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An analysis of cost and duration for deconstruction and demolition of residential buildings in Massachusetts
Resources, Conservation and Recycling 44 (2005) 1–15
An analysis of cost and duration for deconstruction and demolition of residential buildings in Massachusetts Nasiru Dantata, Ali Touran, James Wang∗ Northeastern University Department of Civil and Environmental Engineering, 400 Snell Engineering Center, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA Received 9 April 2004; accepted 20 September 2004
Abstract Deconstruction is an effective means for reducing construction demolition (C&D) debris at a time of diminishing landfill capacities and increased environmental awareness. This paper compares the cost of residential building deconstruction with the cost of demolition in the Commonwealth of Massachusetts. The comparative cost analysis is developed by systematically analyzing two separate residential deconstruction projects previously reported in other studies and augmenting with up-todate cost data for Massachusetts. The study shows that under current conditions in Massachusetts, deconstruction costs could be 17–25% higher than demolition costs. The analysis further identifies and ranks the parameters affecting these costs. These parameters, in the order of their impact on costs are: labor cost (either productivity or hourly rate), disposal cost (tipping fee and transportation), and resale value of deconstructed materials. A sensitivity analysis is used to identify the break-even points for these parameters such that deconstruction becomes economically competitive with demolition. This study demonstrates an approach for planners of waste management programs to evaluate and develop strategies for promoting C&D waste reduction. © 2004 Elsevier B.V. All rights reserved. Keywords: Deconstruction; Construction and demolition waste; Waste management; Cost analysis; Recycling; Waste reduction
∗
Corresponding author. Tel.: +1 617 373 3631; fax: +1 617 373 4419. E-mail address: [email protected] (J. Wang).
0921-3449/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.resconrec.2004.09.001
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1. Introduction Managing solid waste has challenged cities and governments throughout the world. Limited landfill capacity coupled with the difficulty of developing new landfills, especially in the face of environmental concerns and public opposition, has caused regulators to set plans for reducing the disposal of solid waste in landfills. In the United States, the major component of non-municipal solid waste consists of Construction and Demolition (C&D) debris. According to one estimate, approximately 136 million tons of building-related C&D debris was generated in the United States in 1996 (Franklin Associates, 1998). In the Commonwealth of Massachusetts, it is estimated that 95% of non-municipal solid waste is C&D debris (Executive Office, 2000). Although C&D waste is generally inert, and therefore, may not pose an environmental threat as great as hazardous waste or typical municipal solid waste, still its large volume results in a major problem for many communities due to the diminishing disposal capacity. In responding to this concern, Massachusetts has set a goal of reducing the non-municipal waste by 88% by the year 2010 (Executive Office, 2000). One effective means of reducing the volume of C&D waste is to increase and promote the practice of deconstruction. A careful analysis of the costs of deconstruction in Massachusetts will help in planning and formulating policies that can promote C&D waste reduction. Deconstruction, also referred to as selective dismantling, is the process of dismantling building components in the reverse order as how they are originally constructed (Guy and McLendon, 2000). It is a last-in, first-out process. The materials removed are salvaged for reuse or recycling and only those that cannot be reused or recycled are discarded. Deconstruction provides potential economic and environmental benefits compared to the conventional practice of total demolition. The economic benefits come from the salvage materials sold/reused and from the disposal fees avoided. The primary environmental benefit is the reduced waste generation. However, deconstruction may take longer than demolition because of its labor-intensive nature. This paper discusses the economic prospects of deconstruction practices in Massachusetts and the labor requirement and project duration based on the analysis of deconstruction projects and studies previously reported for the Southeast (Florida) and mid-Atlantic (Maryland) regions. Several studies have shown the potential economic and environmental benefits of deconstruction. Among these is a study by the Center for Construction and Environment (CCE) of the University of Florida. The study included deconstructing six (6) houses in 1999 and 2000 “to examine the cost–effectiveness of deconstruction and salvage when compared to traditional demolition” (Guy and McLendon, 2000). The analysis in the CCE report was based on the labor rates, demolition cost, and landfill tipping fees in the Gainesville, Florida area. It is expected that these rates are area-specific and can vary significantly between various regions in the U.S. Another study was done by the National Association of Home Builders (NAHB) Research Center. The report (NAHB, 1997) documents the deconstruction of a 2000 ft2 (SF) building located in Baltimore County, Maryland. A comparative analysis of the deconstruction versus demolition costs is performed using the prevailing wage rates, tipping fees, and demolition fees applicable to Massachusetts. The two research studies mentioned above are used as the basis for this
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analysis. The objective of this study is to evaluate how the impact of certain cost parameters may affect industry’s decisions of adopting deconstruction and the potential delay impact of deconstruction on projects. The results of this study should be also valid for most Northeastern States with labor and housing conditions similar to Massachusetts.
2. Cost analysis The primary cost elements for deconstruction and demolition projects include labor cost and waste disposal cost. With waste reduction as an objective for deconstruction, the labor cost may become the most important parameter in total deconstruction costs (Guy and McLendon, 2000). In this section, a background description for each of the CCE and NAHB studies will be provided followed by estimates for deconstruction and demolition costs using Massachusetts’s costs. An analysis of the sensitivity of deconstruction and demolition cost parameters are also provided.
3. CCE study 3.1. CCE deconstruction study background and results This study includes deconstruction of six wood-framed residential structures in Gainesville, Florida. University of Florida students and Americorps National Civilian Community Corps teams provided the labor for the projects. For each building, all structures were removed from the site, as would be the case in a demolition project. The six structures deconstructed varied in size, location, age, and condition. These buildings range from about 1100–2000 SF with an average size of 1476 SF (Guy and McLendon, 2000). Based on the report, these buildings appear to be comparable to typical residential buildings in Massachusetts. The data collected in the CCE study includes the on-site labor that was subdivided into seven categories: supervision, deconstruction, demolition, processing, nonproduction, clean-up/disposal, and loading/unloading. The amount of waste and salvaged material was also recorded. The net cost for demolition is estimated as the sum of demolition labor and equipment cost, disposal cost, and other costs such as permitting and testing for asbestos and lead. The gross deconstruction cost is calculated as the cost of deconstruction labor plus disposal cost plus other costs such as permitting and testing. The net deconstruction cost is the gross deconstruction cost less salvage. Salvage is the dollar amount gained by selling the materials recovered from the building deconstruction. Table 1 shows the average labor requirement, disposal quantity, estimated demolition costs, and deconstruction costs for the six deconstructed buildings. It should be noted that the salvage value used to calculate the net deconstruction cost is assumed to be at 50% of the estimated retail value of the new material. The calculated total salvage value in Table 1 is an estimate of what is possible because the materials were not actually sold in the CCE study.
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Table 1 CCE study: average costs and salvage summary (source: Guy and McLendon 2000) Average demolition costs Size (SF) Demolition labor/equip ($/SF) Demolition labor/equip (percentage of project total costs) Testing for asbestos and lead ($/SF) Disposal ($/SF) Disposal (#/SF) Disposal (percentage of project total costs) Other costs: permit, etc. ($/SF) Demolition ($/SF)
1476.17 1.74 32.5 0.97 2.17 52.33 40.5 0.48 5.36
Average deconstruction costs Size (SF) Deconstruction labor ($/SF) Deconstruction labor (h/SF) Deconstruction labor (percentage of project total costs) Testing for asbestos and lead ($/SF) Disposal ($/SF) Disposal (#/SF) Disposal (percentage of project total costs) Diversion from landfill (percentage by weight) Other costs ($/SF) Gross deconstruction ($/SF) Salvage ($/SF) Salvage ($/SF at 50% retail value) Net deconstruction cost ($/SF) Net deconstruction cost ($/SF) considering (50% salvage)
1476.17 3.64 0.29 56 0.97 0.97 19.05 15 59.89 0.89 6.47 3.28 1.64 3.19 4.83
Cost comparison Demolition–gross deconstruction ($/SF) = 5.36 − 6.47 Demolition–net deconstruction considering 50% salvage = 5.36 − 4.83
−1.11 0.53
3.2. Applicable cost data for Massachusetts This section presents an estimate for the labor rate, demolition costs, and landfill tipping fees applicable in Massachusetts.
3.2.1. Labor rate Labor rate for a common building laborer for Boston, MA, is $31.30/h in 2001 according to Means (2001). We compare this rate to the data for construction laborers in Massachusetts collected from two other sources. The U.S. Department of Labor data shows that the average Construction Laborer’s wage is $21.29/h for Boston, MA in 2001 (Bureau of Labor Statistics, 2002). The other data is $39.06/h collected from Consigli Construction, a Massachusetts building contractor adopting the practices of source separation and construction recycling (Christoforou, 2002). The $31.30/h from Means will be used and is within the range of the other rates.
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Table 2 A comparison of costs for demolition and deconstruction in Florida and Massachusetts Average costs
CCE study
Massachusetts
Deconstruction productivity (h/SF) Demolition disposal (#/SF) Deconstruction disposal (#/SF) Disposal ($/ton) Deconstruction labor rate ($/h) Demolition labor and equipment ($/SF) Salvage ($/SF)
0.29 52.33 19.05 81.9–101.84 12.50 1.74 3.28
0.29 52.33 19.05 99.2 (sorted), 136.2 (unsorted) 31.30 3.14 3.40
3.2.2. Disposal cost Christoforou (2002) estimated the average disposal costs in Massachusetts using the data collected from Consigli Construction: Landfill tipping fee ($/ton) Transportation cost ($/ton) Disposal cost ($/ton)
83 (sorted) and 120 (unsorted) 16.20 99.20 (sorted) and 136.20 (unsorted)
In the case of deconstruction the cost for sorted waste ($99.2/ton) applies, while in the case of demolition the rate of $136.2/ton for unsorted waste is used. 3.2.3. Demolition cost Demolition costs are estimated using the R.S. Means repair and remodeling cost data (1998). The cost was adjusted using the city factor for Boston. The demolition costs are estimated as $3.14/SF. 3.2.4. Salvage value The salvage value is adjusted using the Means (2001) materials location factor as follows: Location factor for Gainesville, Florida: 100.0. Location factor for Boston, Massachusetts: 103.8. Salvage value for CCE study: $3.28/SF. Estimated salvage value (at 100% retail) for Massachusetts: $3.28 (103.8/100.0) = $3.40/SF. The cost data described above are used to evaluate the deconstruction and demolition costs for Massachusetts. 3.3. Cost comparison for deconstruction and demolition in Massachusetts In estimating the cost of deconstruction and demolition in Massachusetts, deconstruction productivity (labor requirement) and disposal quantity in demolition and deconstruction are assumed to be the same as in the CCE study. Table 2 summarizes the estimated cost parameters for Massachusetts and Florida. Massachusetts’s data presented in Table 2 are used to calculate the average costs for demolition and deconstruction following the method reported in the CCE study (Table 3).
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Table 3 Average deconstruction and demolition costs for Massachusetts (based on CCE study) Deconstruction (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Deconstruction labor ($/SF) = productivity (h/SF) × labor rate ($/h) Productivity (h/SF) Labor rate ($/h) (3) Other costs (tests, permits, general conditions) Other costs ($/SF) (4) Gross deconstruction cost ($/SF) = (1) + (2) + (3) (5) Salvage ($/SF) Salvage ($/SF) (6) Net deconstruction cost assuming 50% salvage, $/SF = (4) − 0.5 × (5) Demolition (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Demolition cost (for MA) ($/SF)
0.94 19.05 99.20 (transport and tipping–sorted waste) 9.11 0.29 31.30 1.86 1.86 11.91 3.4 10.21 3.56 52.33 136.20 (transport and tipping–unsorted) 3.14
(3) Other costs (tests, permits, general conditions) Other costs ($/SF)
1.45 1.45
(4) Total demolition cost ($/SF) = (1) + (2) + (3)
8.15
Demolition—gross deconstruction ($/SF) = 8.15 − 11.91 Demolition—net deconstruction assuming 50% salvage = 8.15 − 10.21
−3.76 −2.06
As seen from Table 3, in Massachusetts deconstruction may not be economically favorable as compared to demolition. Total demolition costs for Massachusetts are estimated at $8.15/SF compared with $5.36/SF estimated for Florida in the CCE study. However, the increase in labor rate and disposal fees between the CCE study and the Massachusetts data has made gross deconstruction costs to be 46% higher than demolition costs. Even the net deconstruction cost using 50% retail value for salvage is still 25% higher than demolition costs. A range of 25–50% of retail prices for salvaged materials was estimated in the CCE study (Guy and McLendon, 2000). A consultation with a local used material dealer in Boston led us to expect that salvaged materials will sell at less than 50% of retail prices. This will make the net deconstruction cost in Massachusetts to be even higher than the one presented in Table 3. The estimated unit costs discussed above can vary within a range due to the contractor’s experience in deconstruction and market conditions. A spider curve is developed to help visualize the effects of changes in the labor productivity, demolition costs, and disposal costs on the overall deconstruction and demolition costs (Fig. 1). The base value of the net deconstruction cost includes an assumed 50% retail value for salvage.
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Fig. 1. Evaluation of deconstruction and demolition costs for Massachusetts using CCE study.
As seen from Fig. 1, deconstruction labor is the most sensitive cost parameter. A decrease of about 20% in labor cost (from base value to 80%) will make net deconstruction costs equal to the base demolition costs. The parameters affecting the net deconstruction cost in the order of decreasing sensitivity are labor cost, salvage value, and disposal cost. A 1% change in the labor cost will change the net deconstruction cost by 0.89% in the same direction. A 1% change in the disposal cost will change the net deconstruction cost by 0.10% in the same direction. The salvage value has an opposite effect on the deconstruction cost. A 1% change in the salvage value will change the net deconstruction cost by 0.17% in the opposite direction. For demolition, disposal cost and demolition costs have similar effects on the total costs, as shown in Fig. 1 that the two lines to be almost identical. A 1% change in the disposal cost will change the total demolition cost by 0.44% and a 1% change in the unit demolition cost will change the total demolition cost by 0.39% in the same direction. 3.4. NAHB case study The NAHB reported an extensive deconstruction study. The report (NAHB, 1997) presents the results of a pilot project of deconstructing a 4-unit, residential building in Baltimore County, Maryland. It also includes a methodology for future deconstruction studies. This methodology was followed in the CCE study discussed earlier. The NAHB report also discusses the economic and environmental benefits of deconstruction and the relevant issues concerning the deconstruction and demolition industry.
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Table 4 NAHB study: comparison of deconstruction and demolition costs (source: NAHB, 1997) Costs/premiums
Deconstruction cost ($)
Labor Marketing Equipment Disposal Recycling (Wood, Masonry, Shingles) Recycling value (metals) Estimated value of salvaged materials Total
11,443 500 0 900 1,000 −250 2,791–4,572 9,021–10,802
Demolition cost ($)
Proprietary information: NA
7,000–10,000
We follow the NAHB’s cost analysis and apply Massachusetts’s rates to assess the viability of deconstruction practices in the Northeast. The background of the NAHB study is presented with a summary of the cost analysis. The reported cost analysis is then adjusted with the estimated labor rates and disposal costs for Massachusetts. 3.5. NAHB study background and results The NAHB case study documented the deconstruction of a two-story, 2000 SF, four-unit residential building in Baltimore County, Maryland, in 1997. Built in 1948, the building is wood-framed and the exterior walls were made of 8-in. double Wythe masonry (4 in. brick, 4 in. CMU). The roof is wood-framed with asphalt shingles cover. The interior walls are plastered over gypsum lath boards. The floors consist of oak strip, vinyl tiles, and ceramic tiles (NAHB, 1997). Key objectives of the NAHB study include finding the labor requirements, job training potential, waste diversion rate, salvageable material, cost comparison of deconstruction to demolition, and the environmental benefits of deconstruction. Our study focuses on the cost comparison and analysis. As in the CCE study, the parameters that affect deconstruction costs include disposal costs, labor rates, market for salvage materials, and job duration. The cost analysis of the NAHB study is summarized in Table 4. The total labor hours spent was 902.5 h including laborers idle time. This means the productivity is 0.45 h/SF of building (902.5/2000). The labor rate assumed is $12/h for semi-skilled laborer and $20/h for the foreman. Marketing cost is the cost of newspaper advertising of the salvage materials. Disposal cost was calculated based on a pull fee of $300 for a 30-cubic yard dumpster. Wood, masonry, and shingles were recycled in the Baltimore area at a cost less than disposal cost. On the other hand, metal recycling represents potential revenue. Salvage value was estimated as a percentage of the retail prices of the new materials. This percentage varies from 0 to 100% depending on the material and its condition. The demolition cost estimate was based on R.S. Means and discussions with demolition contractors. Further breakdown of the cost and productivity can be found in the NAHB study report (NAHB, 1997). The total salvaged and recycled material was estimated at 96.5 tons and about 30.7 tons was landfilled. This represents a 76% waste diversion rate by weight.
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Table 5 A comparison of costs for demolition and deconstruction in Maryland and Massachusetts Average costs
NAHB study
Massachusetts
Deconstruction productivity (h/SF) Demolition disposal (#/SF) Deconstruction disposal (#/SF) Disposal ($/ton) Deconstruction labor rate ($/h) Demolition labor and equipment ($/SF) Salvage value ($/SF)
0.45 127.2 30.7 30.00a 12.00–20.00 3.50–5.00 1.40–2.29
0.45 127.2 30.7 99.20 (sorted), 136.20 (unsorted) 31.30 3.14 1.5–2.45
a
Converted from a volume-based pull fee of $300 per 30-yard dumpster.
The estimated cost parameters for Massachusetts have been described earlier. The salvage value is adjusted using the R.S. Means materials location factor as follows: Location factor for Baltimore, Maryland: 97.1. Location factor for Boston, Massachusetts: 103.8. Salvage value for NAHB study: $1.40/SF–$2.29/SF Estimated salvage value for Massachusetts: 1.40(103.8/97.1) to 2.29(103.8/ 97.1) = $1.50/SF–$2.45/SF. 3.6. Comparative cost analysis for Massachusetts Table 5 summarizes the estimates used in the comparative cost analysis for Massachusetts. Table 6 presents the results of the demolition cost and deconstruction cost estimates for Massachusetts. Other costs, such as testing and permit fees are estimated to be the same as those in the CCE study. These costs are estimated as $1.86/SF for deconstruction and $1.45/SF for demolition. As seen in Table 6, deconstruction is not economically favorable to demolition using Massachusetts cost data. The labor component of deconstruction costs alone is higher than the estimated demolition costs. The salvage value gained is not enough to compensate for the cost difference. The NAHB study shows mid-range net deconstruction cost ($9911.5) to be 17% higher than mid-range demolition costs ($8500) (Table 4). Our comparative analysis for Massachusetts shows net deconstruction cost to be about 14–20% higher than the estimated demolition cost. Deconstruction productivity reported in the NAHB study is much lower than that of the CCE study. One of the reasons is the presence of bricks in the NAHB study. These bricks are also the main reason behind the large amount of disposal in both deconstruction and demolition compared to the CCE study. By comparing the CCE and the NAHB study we conclude that deconstructing brick buildings is less economically attractive compared to deconstructing wood frame buildings. Fig. 2 presents a spider curve showing the changes of deconstruction and demolition costs due to changes in individual cost parameters. The base cost for deconstruction includes the estimated salvage (Table 6). Deconstruction labor is the most sensitive cost parameter, same as the observation shown in Fig. 1. The parameters affecting the net deconstruction cost in the order of decreasing sensitivity are labor cost, salvage value, and disposal cost. A
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Table 6 Average deconstruction and demolition costs for Massachusetts (based on NAHB study) Deconstruction (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Deconstruction labor ($/SF) = productivity (h/SF) × labor rate ($/h) Productivity (h/SF) Labor rate ($/h) (3) Other costs (tests, permits, general conditions) Other costs ($/SF) (4) Gross deconstruction cost ($/SF) = (1) + (2) + (3) (5) Salvage ($/SF) Salvage ($/SF) (6) Net deconstruction cost 50% salvage, $/SF = (4) − (5) Demolition (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Demolition cost (for MA) ($/SF) (3) Other costs (tests, permits, general conditions) Other costs ($/SF)
1.52 30.7 99.20 (transport and tipping–sorted waste) 14.12 0.45 31.30 1.86 1.86 17.50 1.5–2.45 15.05–16.00 (mid-range: 15.53) 8.66 127.2 136.20 (transport and tipping–unsorted) 3.14 1.45 1.45
(4) Total demolition cost ($/SF) = (1) + (2) + (3)
13.25
Demolition—gross deconstruction ($/SF) Demolition—net deconstruction ($/SF) (mid-range)
−4.25 −2.27
1% change in the labor cost will change the net deconstruction cost by 0.91% in the same direction. A 1% change in the disposal cost will change the net deconstruction cost by 0.10% in the same direction. The salvage value has an opposite effect on the deconstruction cost. A 1% change in the salvage value will change the net deconstruction cost by 0.13% in the opposite direction. For demolition, the unit disposal cost is the more sensitive parameter. A 1% change in the unit disposal cost will change the total demolition cost by 0.65% and a 1% change in the unit demolition cost will change the total demolition cost by 0.24% in the same direction. This is different from the observation made in Fig. 1 where two parameters have very similar effects on the overall demolition cost. Similar to the observation made in Fig. 1, one break-even point is reached when deconstruction labor cost is lowered by 15%. An interesting observation in Fig. 2 is the additional scenario in which the costs for deconstruction and demolition are comparable. A second break-even point is reached when the disposal costs for deconstruction and demolition both increase by 30%. This result suggests that deconstruction may become a competitive, or even attractive, option in a region where disposal capacity diminishes quickly resulting in a fast-rising disposal cost for C&D waste.
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Fig. 2. Evaluation of deconstruction and demolition costs for Massachusetts using NAHB study.
4. Deconstruction duration and labor requirement The time required to deconstruct a house is of particular importance when the deconstruction site is slated for redevelopment. Deconstruction time includes the time to remove all materials and clean the site. It is expected that the time required for deconstruction depend partly on the labor utilized. Both deconstruction duration and labor utilization affect the overall deconstruction cost. We examine five published deconstruction studies to assess the project duration and labor requirement for deconstruction of residential buildings. 4.1. Study no. 1 This is the CCE study described in previous sections. The average building size was 1476 SF and the average man-hours for deconstruction was 429 h (Guy and McLendon, 2000). This amounts to deconstruction productivity of 0.29 h/SF. Assuming a crew size of five laborers, working 8 h a day, it will take ten working days to finish the job. 4.2. Study no. 2 DeConstruction Services, a deconstruction contractor in Portland, Oregon, deconstructed three buildings in 9 days with a crew size of 25 workers (Emmaus, 2001). This translates into on average 3 days per building. Although the building square footage was not reported, the deconstruction duration appears to compare well with the CCE study mentioned above after factoring in the crew size.
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Table 7 Summary of deconstruction duration studies Building size (SF)
Crew size (laborers)
Duration, working days (8 h/day)
Duration (days/1000) (SF)
Actual (h/SF)
Study reference
1,476a – 1,280
5 25 –
10b 3b 10
6.78 – 7.81
0.29 – –
3,600 2,000
– 6
9b 15
2.50 7.50
– 0.45
CCE (2000) Emmaus (2001) The Air Force Center for Environmental Excellence (2003) Cosper (2000) NAHB (1997)
a b
Average of several projects included in the report. Estimate based on reported labor hours.
4.3. Study no. 3 The U.S. Air Force Center for Environmental Excellence reported a case study of deconstructing a 1280 SF house. It took 2 weeks (10 working days) to complete the deconstruction. The report also estimated the required demolition time for the same building would be 2 days (The Air Force Center for Environmental Excellence, 2003). 4.4. Study no. 4 An Army Corps of Engineers’ report estimated that a typical wood-framed building (3600 SF) can be demolished in 3 days and deconstruction will take about three times as much, or about nine working days (Cosper, 2000). However, the report did not specify the crew size. 4.5. Study no. 5 This is the NAHB pilot project described in previous sections (NAHB, 1997). A twostory, four-unit, 2000 SF residential building was deconstructed in 15 working days. The total labor hours were 902.5. This represents a deconstruction productivity of 0.45 h/SF. The labor crew consisted of five laborers and a foreman. Based on the case studies described above, the reported time to deconstruct a residential building of 1000–2000 SF ranges from 10 to 15 working days using a crew size of 5–6 workers (Table 7). Demolition of the same building may be completed in just one-fifth to one-third of the time required for deconstruction (The Air Force Center for Environmental Excellence, 2003; Cosper, 2000). The project duration for the 3600 SF building in Table 7 is only an estimate and the building was not actually deconstructed. The first three cases in Table 7 show that the duration to deconstruct a residential building is on average 7.4 working days per 1000 SF of building. This is the project duration estimated for building size of 1000–2000 SF and a crew size of five laborers. Deconstruction can potentially be completed in a timelier manner if a larger crew size or a more experienced crew is utilized.
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Table 8 Cost of deconstruction delay
Square foot (SF) Cost ($/SF)a (Means, 2002) Home office overhead rate (Means, 1998) (percentage of direct costs) Construction duration (weeks) Total overhead ($/SF) Overhead per week ($/SF/week) Deconstruction duration (weeks) Demolition durationd Delay due to deconstruction Effect of delay on cost ($/SF) (additional overhead) Average additional overhead ($/SF)
Average one-story
Average two-story
1600 77.52
1600 74.68
3400 60.82 7.70
26b 5.97 0.2296 2.4 0.6 1.8 0.41
3200 61.50 7.70
40c 4.68 0.1171 5.0 1.3 3.7 0.43 0.42
26b 5.75 0.2212 2.4 0.6 1.8 0.40
40c 4.74 0.1184 5.0 1.3 3.7 0.44 0.42
a
$/SF, cost adjusted by average location factor of 1.054 for Massachusetts (Means, 2002). Allen and Thallon (2002). c Estimate from local contractor. d Twenty-five percent of deconstruction duration, average from The Air Force Center for Environmental Excellence (2003) and Cosper (2000). b
5. Potential cost of deconstruction due to project duration Deconstruction, as discussed above, may lengthen the overall project duration as compared to demolition. To estimate the cost of this delay we took into account the contractor’s overhead costs during the delay period. Contractor’s weekly overhead is estimated using R.S. Means data and average construction duration. Multiplying this overhead cost by the potential delay due to deconstruction duration provides an estimate of the additional cost of deconstruction due to schedule delay. The average cost of deconstruction delay for one- and two-story, 1600–3400 SF, homes is estimated as $0.42/SF (Table 8). This is approximately 0.6% of the average total construction cost. Furthermore, for redevelopment projects there will be finance charges to the developer. These charges are not considered in our analysis because they vary widely by the project type and owner.
6. Summary and conclusion Similar conclusions are reached in our analyses based on the CCE study and the NAHB study. The adjusted cost analyses of the CCE and NAHB case studies using current Massachusetts’s cost data show that deconstruction is less favorable to total demolition. Our analyses suggest that in Massachusetts’s net deconstruction costs may vary between $10.21/SF and $15.53/SF, while demolition costs are estimated as between $8.15/SF and $13.25/SF. This shows deconstruction costs for Massachusetts could be 17% (adjusted from NAHB study) to 25% (adjusted from CCE study) higher than demolition costs.
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Table 9 Sensitivity of cost parameters in demolition and deconstruction Parameter
Net deconstruction cost Labor cost Disposal cost Salvage value Total demolition cost Disposal cost Demolition cost
Percentage change in Massachusetts net deconstruction or demolition costs due to a 1% change in parameter Based on CCE study
Based on NAHB study
0.89 0.10 −0.17
0.91 0.10 −0.13
0.44 0.39
0.65 0.24
Table 9 presents a summary of the potential effects of selected cost parameters on the overall deconstruction and demolition costs. As shown in Table 9, the sensitivities of cost parameters are consistent across the two studies used as the basis for our analysis for Massachusetts. For net deconstruction cost, the most sensitive cost parameter is the labor cost, followed by the salvage value, and lastly the disposal cost. For total demolition cost, the most sensitive parameter is the disposal cost for both studies. In each of our analyses for Massachusetts, we apply the productivity and waste generation rate reported in the CEE and NAHB studies. Deconstruction in Massachusetts will become more favorable if productivity increases or lower wage rate or higher disposal cost applies. While disposal cost and wage rate may be predominately controlled by the market, contractors may improve their deconstruction productivity through training, planning, and experience. Such experience-building practice is worth considering for contractors in the region where disposal cost is likely to continue to increase. The productivity in the NAHB study is much lower than that in the CEE study. The main cause is likely that the NAHB building had brick walls while none of the six buildings in the CCE study had bricks. The cost difference between deconstruction and demolition is even higher if the impact of extended project duration caused by deconstruction is considered. Residential deconstruction duration is estimated at 7.4 working days per 1000 SF with a crew of five laborers. We estimated the additional contractor overhead cost of deconstruction delay for one- and two-story, 1600–3400 SF, homes as $0.42/SF. When considering deconstruction, a building’s condition should be evaluated to see how much salvage could be recovered and a cost analysis similar to the one done in this report will provide a quick way to compare deconstruction and demolition costs. Deconstruction is also attractive when access to the site is limited because demolitions usually require larger space for equipment. In urban settings where the lack of space can slow down the demolition process, deconstruction may be a reasonable alternative. Future deconstruction studies should pay more attention to the time requirement compared to demolition especially on lands that are scheduled for immediate redevelopment. Deconstruction is most preferable to demolition when there is no such time constraint. Deconstruction represents an effective option for reducing C&D waste generation. Certain cost parameters associated with the deconstruction practice may vary among different regions. A comparative cost analysis can provide an insight as how each cost parameter
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may impact the overall costs. Such analysis can also help us identify the conditions under which deconstruction can be cost–effective. Our analyses suggest that both improved deconstruction productivity and increased waste disposal costs represent such opportunities. This study also demonstrates an approach for planners of regional waste management programs to evaluate and develop strategies for promoting C&D waste reduction.
References Allen E, Thallon R. Fundamentals of residential construction. New York, N.Y.: John Wiley and Sons Inc.; 2002. Bureau of Labor Statistics. 2001 metropolitan area occupational employment and wage estimates. Division of Occupational Employment Statistics, U.S. Department of Labor, Bureau of Labor Statistics; 2002, http://www.bls.gov/oes/2001/oes 1120.htm-b47-0000, last accessed April 7, 2003. Christoforou C. A systems analysis tool to assist decisions in construction and demolition waste management. M.S. Thesis. Boston, MA: Northeastern University; 2002. Cosper SD. Selection of demolition reduction, reuse, and reduction, reuse, and recycling methods recycling methods. Charlotte NRC, Charlotte, NC: Construction Engineering Research Laboratory’ NRC; 2000. Emmaus A. Taking the deconstruction road to C&D management. BioCycle 2001;42(5):42 [JG Press Inc.]. Executive Office of Environmental Affairs. Beyond 2000—solid waste master plan. Commonwealth of Massachusetts: Department of Environmental Protection; December 2000. Franklin Associates. Characterization of building-related construction and demolition debris in the United States. Report no. EPA530-R-98-010. EPA; June 1998. Guy B, McLendon S. Building deconstruction: reuse and recycling of building materials. Florida: Center for Construction and Environment, University of Florida; 2000. NAHB Research Center Inc. Deconstruction—building disassembly and material salvage: the Riverdale cast study. Maryland, MD: NAHB; 1997. Means RS. 1999 RS Means building construction cost data. 57th Annual ed. MA: RSMeans Company Inc.; 1998. Means RS. R.S. Means 1999 repair & remodeling cost data. MA: RSMeans Company Inc.; 1998. Means RS. 2002 RSMeans square foot costs. 23rd Annual ed. MA: RSMeans Company Inc.; 2001. The Air Force Center for Environmental Excellence. C&D waste management guide. Brooks AFB, San Antonio, Texas: The Air Force Center for Environmental Excellence; 2003, http://www.afcee.brooks. af.mil/green/resources/cdguide.exe, last accessed April 7, 2003.
An analysis of cost and duration for deconstruction and demolition of residential buildings in Massachusetts Nasiru Dantata, Ali Touran, James Wang∗ Northeastern University Department of Civil and Environmental Engineering, 400 Snell Engineering Center, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA Received 9 April 2004; accepted 20 September 2004
Abstract Deconstruction is an effective means for reducing construction demolition (C&D) debris at a time of diminishing landfill capacities and increased environmental awareness. This paper compares the cost of residential building deconstruction with the cost of demolition in the Commonwealth of Massachusetts. The comparative cost analysis is developed by systematically analyzing two separate residential deconstruction projects previously reported in other studies and augmenting with up-todate cost data for Massachusetts. The study shows that under current conditions in Massachusetts, deconstruction costs could be 17–25% higher than demolition costs. The analysis further identifies and ranks the parameters affecting these costs. These parameters, in the order of their impact on costs are: labor cost (either productivity or hourly rate), disposal cost (tipping fee and transportation), and resale value of deconstructed materials. A sensitivity analysis is used to identify the break-even points for these parameters such that deconstruction becomes economically competitive with demolition. This study demonstrates an approach for planners of waste management programs to evaluate and develop strategies for promoting C&D waste reduction. © 2004 Elsevier B.V. All rights reserved. Keywords: Deconstruction; Construction and demolition waste; Waste management; Cost analysis; Recycling; Waste reduction
∗
Corresponding author. Tel.: +1 617 373 3631; fax: +1 617 373 4419. E-mail address: [email protected] (J. Wang).
0921-3449/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.resconrec.2004.09.001
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1. Introduction Managing solid waste has challenged cities and governments throughout the world. Limited landfill capacity coupled with the difficulty of developing new landfills, especially in the face of environmental concerns and public opposition, has caused regulators to set plans for reducing the disposal of solid waste in landfills. In the United States, the major component of non-municipal solid waste consists of Construction and Demolition (C&D) debris. According to one estimate, approximately 136 million tons of building-related C&D debris was generated in the United States in 1996 (Franklin Associates, 1998). In the Commonwealth of Massachusetts, it is estimated that 95% of non-municipal solid waste is C&D debris (Executive Office, 2000). Although C&D waste is generally inert, and therefore, may not pose an environmental threat as great as hazardous waste or typical municipal solid waste, still its large volume results in a major problem for many communities due to the diminishing disposal capacity. In responding to this concern, Massachusetts has set a goal of reducing the non-municipal waste by 88% by the year 2010 (Executive Office, 2000). One effective means of reducing the volume of C&D waste is to increase and promote the practice of deconstruction. A careful analysis of the costs of deconstruction in Massachusetts will help in planning and formulating policies that can promote C&D waste reduction. Deconstruction, also referred to as selective dismantling, is the process of dismantling building components in the reverse order as how they are originally constructed (Guy and McLendon, 2000). It is a last-in, first-out process. The materials removed are salvaged for reuse or recycling and only those that cannot be reused or recycled are discarded. Deconstruction provides potential economic and environmental benefits compared to the conventional practice of total demolition. The economic benefits come from the salvage materials sold/reused and from the disposal fees avoided. The primary environmental benefit is the reduced waste generation. However, deconstruction may take longer than demolition because of its labor-intensive nature. This paper discusses the economic prospects of deconstruction practices in Massachusetts and the labor requirement and project duration based on the analysis of deconstruction projects and studies previously reported for the Southeast (Florida) and mid-Atlantic (Maryland) regions. Several studies have shown the potential economic and environmental benefits of deconstruction. Among these is a study by the Center for Construction and Environment (CCE) of the University of Florida. The study included deconstructing six (6) houses in 1999 and 2000 “to examine the cost–effectiveness of deconstruction and salvage when compared to traditional demolition” (Guy and McLendon, 2000). The analysis in the CCE report was based on the labor rates, demolition cost, and landfill tipping fees in the Gainesville, Florida area. It is expected that these rates are area-specific and can vary significantly between various regions in the U.S. Another study was done by the National Association of Home Builders (NAHB) Research Center. The report (NAHB, 1997) documents the deconstruction of a 2000 ft2 (SF) building located in Baltimore County, Maryland. A comparative analysis of the deconstruction versus demolition costs is performed using the prevailing wage rates, tipping fees, and demolition fees applicable to Massachusetts. The two research studies mentioned above are used as the basis for this
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analysis. The objective of this study is to evaluate how the impact of certain cost parameters may affect industry’s decisions of adopting deconstruction and the potential delay impact of deconstruction on projects. The results of this study should be also valid for most Northeastern States with labor and housing conditions similar to Massachusetts.
2. Cost analysis The primary cost elements for deconstruction and demolition projects include labor cost and waste disposal cost. With waste reduction as an objective for deconstruction, the labor cost may become the most important parameter in total deconstruction costs (Guy and McLendon, 2000). In this section, a background description for each of the CCE and NAHB studies will be provided followed by estimates for deconstruction and demolition costs using Massachusetts’s costs. An analysis of the sensitivity of deconstruction and demolition cost parameters are also provided.
3. CCE study 3.1. CCE deconstruction study background and results This study includes deconstruction of six wood-framed residential structures in Gainesville, Florida. University of Florida students and Americorps National Civilian Community Corps teams provided the labor for the projects. For each building, all structures were removed from the site, as would be the case in a demolition project. The six structures deconstructed varied in size, location, age, and condition. These buildings range from about 1100–2000 SF with an average size of 1476 SF (Guy and McLendon, 2000). Based on the report, these buildings appear to be comparable to typical residential buildings in Massachusetts. The data collected in the CCE study includes the on-site labor that was subdivided into seven categories: supervision, deconstruction, demolition, processing, nonproduction, clean-up/disposal, and loading/unloading. The amount of waste and salvaged material was also recorded. The net cost for demolition is estimated as the sum of demolition labor and equipment cost, disposal cost, and other costs such as permitting and testing for asbestos and lead. The gross deconstruction cost is calculated as the cost of deconstruction labor plus disposal cost plus other costs such as permitting and testing. The net deconstruction cost is the gross deconstruction cost less salvage. Salvage is the dollar amount gained by selling the materials recovered from the building deconstruction. Table 1 shows the average labor requirement, disposal quantity, estimated demolition costs, and deconstruction costs for the six deconstructed buildings. It should be noted that the salvage value used to calculate the net deconstruction cost is assumed to be at 50% of the estimated retail value of the new material. The calculated total salvage value in Table 1 is an estimate of what is possible because the materials were not actually sold in the CCE study.
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Table 1 CCE study: average costs and salvage summary (source: Guy and McLendon 2000) Average demolition costs Size (SF) Demolition labor/equip ($/SF) Demolition labor/equip (percentage of project total costs) Testing for asbestos and lead ($/SF) Disposal ($/SF) Disposal (#/SF) Disposal (percentage of project total costs) Other costs: permit, etc. ($/SF) Demolition ($/SF)
1476.17 1.74 32.5 0.97 2.17 52.33 40.5 0.48 5.36
Average deconstruction costs Size (SF) Deconstruction labor ($/SF) Deconstruction labor (h/SF) Deconstruction labor (percentage of project total costs) Testing for asbestos and lead ($/SF) Disposal ($/SF) Disposal (#/SF) Disposal (percentage of project total costs) Diversion from landfill (percentage by weight) Other costs ($/SF) Gross deconstruction ($/SF) Salvage ($/SF) Salvage ($/SF at 50% retail value) Net deconstruction cost ($/SF) Net deconstruction cost ($/SF) considering (50% salvage)
1476.17 3.64 0.29 56 0.97 0.97 19.05 15 59.89 0.89 6.47 3.28 1.64 3.19 4.83
Cost comparison Demolition–gross deconstruction ($/SF) = 5.36 − 6.47 Demolition–net deconstruction considering 50% salvage = 5.36 − 4.83
−1.11 0.53
3.2. Applicable cost data for Massachusetts This section presents an estimate for the labor rate, demolition costs, and landfill tipping fees applicable in Massachusetts.
3.2.1. Labor rate Labor rate for a common building laborer for Boston, MA, is $31.30/h in 2001 according to Means (2001). We compare this rate to the data for construction laborers in Massachusetts collected from two other sources. The U.S. Department of Labor data shows that the average Construction Laborer’s wage is $21.29/h for Boston, MA in 2001 (Bureau of Labor Statistics, 2002). The other data is $39.06/h collected from Consigli Construction, a Massachusetts building contractor adopting the practices of source separation and construction recycling (Christoforou, 2002). The $31.30/h from Means will be used and is within the range of the other rates.
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Table 2 A comparison of costs for demolition and deconstruction in Florida and Massachusetts Average costs
CCE study
Massachusetts
Deconstruction productivity (h/SF) Demolition disposal (#/SF) Deconstruction disposal (#/SF) Disposal ($/ton) Deconstruction labor rate ($/h) Demolition labor and equipment ($/SF) Salvage ($/SF)
0.29 52.33 19.05 81.9–101.84 12.50 1.74 3.28
0.29 52.33 19.05 99.2 (sorted), 136.2 (unsorted) 31.30 3.14 3.40
3.2.2. Disposal cost Christoforou (2002) estimated the average disposal costs in Massachusetts using the data collected from Consigli Construction: Landfill tipping fee ($/ton) Transportation cost ($/ton) Disposal cost ($/ton)
83 (sorted) and 120 (unsorted) 16.20 99.20 (sorted) and 136.20 (unsorted)
In the case of deconstruction the cost for sorted waste ($99.2/ton) applies, while in the case of demolition the rate of $136.2/ton for unsorted waste is used. 3.2.3. Demolition cost Demolition costs are estimated using the R.S. Means repair and remodeling cost data (1998). The cost was adjusted using the city factor for Boston. The demolition costs are estimated as $3.14/SF. 3.2.4. Salvage value The salvage value is adjusted using the Means (2001) materials location factor as follows: Location factor for Gainesville, Florida: 100.0. Location factor for Boston, Massachusetts: 103.8. Salvage value for CCE study: $3.28/SF. Estimated salvage value (at 100% retail) for Massachusetts: $3.28 (103.8/100.0) = $3.40/SF. The cost data described above are used to evaluate the deconstruction and demolition costs for Massachusetts. 3.3. Cost comparison for deconstruction and demolition in Massachusetts In estimating the cost of deconstruction and demolition in Massachusetts, deconstruction productivity (labor requirement) and disposal quantity in demolition and deconstruction are assumed to be the same as in the CCE study. Table 2 summarizes the estimated cost parameters for Massachusetts and Florida. Massachusetts’s data presented in Table 2 are used to calculate the average costs for demolition and deconstruction following the method reported in the CCE study (Table 3).
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Table 3 Average deconstruction and demolition costs for Massachusetts (based on CCE study) Deconstruction (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Deconstruction labor ($/SF) = productivity (h/SF) × labor rate ($/h) Productivity (h/SF) Labor rate ($/h) (3) Other costs (tests, permits, general conditions) Other costs ($/SF) (4) Gross deconstruction cost ($/SF) = (1) + (2) + (3) (5) Salvage ($/SF) Salvage ($/SF) (6) Net deconstruction cost assuming 50% salvage, $/SF = (4) − 0.5 × (5) Demolition (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Demolition cost (for MA) ($/SF)
0.94 19.05 99.20 (transport and tipping–sorted waste) 9.11 0.29 31.30 1.86 1.86 11.91 3.4 10.21 3.56 52.33 136.20 (transport and tipping–unsorted) 3.14
(3) Other costs (tests, permits, general conditions) Other costs ($/SF)
1.45 1.45
(4) Total demolition cost ($/SF) = (1) + (2) + (3)
8.15
Demolition—gross deconstruction ($/SF) = 8.15 − 11.91 Demolition—net deconstruction assuming 50% salvage = 8.15 − 10.21
−3.76 −2.06
As seen from Table 3, in Massachusetts deconstruction may not be economically favorable as compared to demolition. Total demolition costs for Massachusetts are estimated at $8.15/SF compared with $5.36/SF estimated for Florida in the CCE study. However, the increase in labor rate and disposal fees between the CCE study and the Massachusetts data has made gross deconstruction costs to be 46% higher than demolition costs. Even the net deconstruction cost using 50% retail value for salvage is still 25% higher than demolition costs. A range of 25–50% of retail prices for salvaged materials was estimated in the CCE study (Guy and McLendon, 2000). A consultation with a local used material dealer in Boston led us to expect that salvaged materials will sell at less than 50% of retail prices. This will make the net deconstruction cost in Massachusetts to be even higher than the one presented in Table 3. The estimated unit costs discussed above can vary within a range due to the contractor’s experience in deconstruction and market conditions. A spider curve is developed to help visualize the effects of changes in the labor productivity, demolition costs, and disposal costs on the overall deconstruction and demolition costs (Fig. 1). The base value of the net deconstruction cost includes an assumed 50% retail value for salvage.
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Fig. 1. Evaluation of deconstruction and demolition costs for Massachusetts using CCE study.
As seen from Fig. 1, deconstruction labor is the most sensitive cost parameter. A decrease of about 20% in labor cost (from base value to 80%) will make net deconstruction costs equal to the base demolition costs. The parameters affecting the net deconstruction cost in the order of decreasing sensitivity are labor cost, salvage value, and disposal cost. A 1% change in the labor cost will change the net deconstruction cost by 0.89% in the same direction. A 1% change in the disposal cost will change the net deconstruction cost by 0.10% in the same direction. The salvage value has an opposite effect on the deconstruction cost. A 1% change in the salvage value will change the net deconstruction cost by 0.17% in the opposite direction. For demolition, disposal cost and demolition costs have similar effects on the total costs, as shown in Fig. 1 that the two lines to be almost identical. A 1% change in the disposal cost will change the total demolition cost by 0.44% and a 1% change in the unit demolition cost will change the total demolition cost by 0.39% in the same direction. 3.4. NAHB case study The NAHB reported an extensive deconstruction study. The report (NAHB, 1997) presents the results of a pilot project of deconstructing a 4-unit, residential building in Baltimore County, Maryland. It also includes a methodology for future deconstruction studies. This methodology was followed in the CCE study discussed earlier. The NAHB report also discusses the economic and environmental benefits of deconstruction and the relevant issues concerning the deconstruction and demolition industry.
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Table 4 NAHB study: comparison of deconstruction and demolition costs (source: NAHB, 1997) Costs/premiums
Deconstruction cost ($)
Labor Marketing Equipment Disposal Recycling (Wood, Masonry, Shingles) Recycling value (metals) Estimated value of salvaged materials Total
11,443 500 0 900 1,000 −250 2,791–4,572 9,021–10,802
Demolition cost ($)
Proprietary information: NA
7,000–10,000
We follow the NAHB’s cost analysis and apply Massachusetts’s rates to assess the viability of deconstruction practices in the Northeast. The background of the NAHB study is presented with a summary of the cost analysis. The reported cost analysis is then adjusted with the estimated labor rates and disposal costs for Massachusetts. 3.5. NAHB study background and results The NAHB case study documented the deconstruction of a two-story, 2000 SF, four-unit residential building in Baltimore County, Maryland, in 1997. Built in 1948, the building is wood-framed and the exterior walls were made of 8-in. double Wythe masonry (4 in. brick, 4 in. CMU). The roof is wood-framed with asphalt shingles cover. The interior walls are plastered over gypsum lath boards. The floors consist of oak strip, vinyl tiles, and ceramic tiles (NAHB, 1997). Key objectives of the NAHB study include finding the labor requirements, job training potential, waste diversion rate, salvageable material, cost comparison of deconstruction to demolition, and the environmental benefits of deconstruction. Our study focuses on the cost comparison and analysis. As in the CCE study, the parameters that affect deconstruction costs include disposal costs, labor rates, market for salvage materials, and job duration. The cost analysis of the NAHB study is summarized in Table 4. The total labor hours spent was 902.5 h including laborers idle time. This means the productivity is 0.45 h/SF of building (902.5/2000). The labor rate assumed is $12/h for semi-skilled laborer and $20/h for the foreman. Marketing cost is the cost of newspaper advertising of the salvage materials. Disposal cost was calculated based on a pull fee of $300 for a 30-cubic yard dumpster. Wood, masonry, and shingles were recycled in the Baltimore area at a cost less than disposal cost. On the other hand, metal recycling represents potential revenue. Salvage value was estimated as a percentage of the retail prices of the new materials. This percentage varies from 0 to 100% depending on the material and its condition. The demolition cost estimate was based on R.S. Means and discussions with demolition contractors. Further breakdown of the cost and productivity can be found in the NAHB study report (NAHB, 1997). The total salvaged and recycled material was estimated at 96.5 tons and about 30.7 tons was landfilled. This represents a 76% waste diversion rate by weight.
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Table 5 A comparison of costs for demolition and deconstruction in Maryland and Massachusetts Average costs
NAHB study
Massachusetts
Deconstruction productivity (h/SF) Demolition disposal (#/SF) Deconstruction disposal (#/SF) Disposal ($/ton) Deconstruction labor rate ($/h) Demolition labor and equipment ($/SF) Salvage value ($/SF)
0.45 127.2 30.7 30.00a 12.00–20.00 3.50–5.00 1.40–2.29
0.45 127.2 30.7 99.20 (sorted), 136.20 (unsorted) 31.30 3.14 1.5–2.45
a
Converted from a volume-based pull fee of $300 per 30-yard dumpster.
The estimated cost parameters for Massachusetts have been described earlier. The salvage value is adjusted using the R.S. Means materials location factor as follows: Location factor for Baltimore, Maryland: 97.1. Location factor for Boston, Massachusetts: 103.8. Salvage value for NAHB study: $1.40/SF–$2.29/SF Estimated salvage value for Massachusetts: 1.40(103.8/97.1) to 2.29(103.8/ 97.1) = $1.50/SF–$2.45/SF. 3.6. Comparative cost analysis for Massachusetts Table 5 summarizes the estimates used in the comparative cost analysis for Massachusetts. Table 6 presents the results of the demolition cost and deconstruction cost estimates for Massachusetts. Other costs, such as testing and permit fees are estimated to be the same as those in the CCE study. These costs are estimated as $1.86/SF for deconstruction and $1.45/SF for demolition. As seen in Table 6, deconstruction is not economically favorable to demolition using Massachusetts cost data. The labor component of deconstruction costs alone is higher than the estimated demolition costs. The salvage value gained is not enough to compensate for the cost difference. The NAHB study shows mid-range net deconstruction cost ($9911.5) to be 17% higher than mid-range demolition costs ($8500) (Table 4). Our comparative analysis for Massachusetts shows net deconstruction cost to be about 14–20% higher than the estimated demolition cost. Deconstruction productivity reported in the NAHB study is much lower than that of the CCE study. One of the reasons is the presence of bricks in the NAHB study. These bricks are also the main reason behind the large amount of disposal in both deconstruction and demolition compared to the CCE study. By comparing the CCE and the NAHB study we conclude that deconstructing brick buildings is less economically attractive compared to deconstructing wood frame buildings. Fig. 2 presents a spider curve showing the changes of deconstruction and demolition costs due to changes in individual cost parameters. The base cost for deconstruction includes the estimated salvage (Table 6). Deconstruction labor is the most sensitive cost parameter, same as the observation shown in Fig. 1. The parameters affecting the net deconstruction cost in the order of decreasing sensitivity are labor cost, salvage value, and disposal cost. A
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Table 6 Average deconstruction and demolition costs for Massachusetts (based on NAHB study) Deconstruction (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Deconstruction labor ($/SF) = productivity (h/SF) × labor rate ($/h) Productivity (h/SF) Labor rate ($/h) (3) Other costs (tests, permits, general conditions) Other costs ($/SF) (4) Gross deconstruction cost ($/SF) = (1) + (2) + (3) (5) Salvage ($/SF) Salvage ($/SF) (6) Net deconstruction cost 50% salvage, $/SF = (4) − (5) Demolition (1) Disposal ($/SF) = disposal (#/SF)/2000 × disposal cost ($/ton) Disposal (#/SF) Disposal cost ($/ton) (2) Demolition cost (for MA) ($/SF) (3) Other costs (tests, permits, general conditions) Other costs ($/SF)
1.52 30.7 99.20 (transport and tipping–sorted waste) 14.12 0.45 31.30 1.86 1.86 17.50 1.5–2.45 15.05–16.00 (mid-range: 15.53) 8.66 127.2 136.20 (transport and tipping–unsorted) 3.14 1.45 1.45
(4) Total demolition cost ($/SF) = (1) + (2) + (3)
13.25
Demolition—gross deconstruction ($/SF) Demolition—net deconstruction ($/SF) (mid-range)
−4.25 −2.27
1% change in the labor cost will change the net deconstruction cost by 0.91% in the same direction. A 1% change in the disposal cost will change the net deconstruction cost by 0.10% in the same direction. The salvage value has an opposite effect on the deconstruction cost. A 1% change in the salvage value will change the net deconstruction cost by 0.13% in the opposite direction. For demolition, the unit disposal cost is the more sensitive parameter. A 1% change in the unit disposal cost will change the total demolition cost by 0.65% and a 1% change in the unit demolition cost will change the total demolition cost by 0.24% in the same direction. This is different from the observation made in Fig. 1 where two parameters have very similar effects on the overall demolition cost. Similar to the observation made in Fig. 1, one break-even point is reached when deconstruction labor cost is lowered by 15%. An interesting observation in Fig. 2 is the additional scenario in which the costs for deconstruction and demolition are comparable. A second break-even point is reached when the disposal costs for deconstruction and demolition both increase by 30%. This result suggests that deconstruction may become a competitive, or even attractive, option in a region where disposal capacity diminishes quickly resulting in a fast-rising disposal cost for C&D waste.
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Fig. 2. Evaluation of deconstruction and demolition costs for Massachusetts using NAHB study.
4. Deconstruction duration and labor requirement The time required to deconstruct a house is of particular importance when the deconstruction site is slated for redevelopment. Deconstruction time includes the time to remove all materials and clean the site. It is expected that the time required for deconstruction depend partly on the labor utilized. Both deconstruction duration and labor utilization affect the overall deconstruction cost. We examine five published deconstruction studies to assess the project duration and labor requirement for deconstruction of residential buildings. 4.1. Study no. 1 This is the CCE study described in previous sections. The average building size was 1476 SF and the average man-hours for deconstruction was 429 h (Guy and McLendon, 2000). This amounts to deconstruction productivity of 0.29 h/SF. Assuming a crew size of five laborers, working 8 h a day, it will take ten working days to finish the job. 4.2. Study no. 2 DeConstruction Services, a deconstruction contractor in Portland, Oregon, deconstructed three buildings in 9 days with a crew size of 25 workers (Emmaus, 2001). This translates into on average 3 days per building. Although the building square footage was not reported, the deconstruction duration appears to compare well with the CCE study mentioned above after factoring in the crew size.
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Table 7 Summary of deconstruction duration studies Building size (SF)
Crew size (laborers)
Duration, working days (8 h/day)
Duration (days/1000) (SF)
Actual (h/SF)
Study reference
1,476a – 1,280
5 25 –
10b 3b 10
6.78 – 7.81
0.29 – –
3,600 2,000
– 6
9b 15
2.50 7.50
– 0.45
CCE (2000) Emmaus (2001) The Air Force Center for Environmental Excellence (2003) Cosper (2000) NAHB (1997)
a b
Average of several projects included in the report. Estimate based on reported labor hours.
4.3. Study no. 3 The U.S. Air Force Center for Environmental Excellence reported a case study of deconstructing a 1280 SF house. It took 2 weeks (10 working days) to complete the deconstruction. The report also estimated the required demolition time for the same building would be 2 days (The Air Force Center for Environmental Excellence, 2003). 4.4. Study no. 4 An Army Corps of Engineers’ report estimated that a typical wood-framed building (3600 SF) can be demolished in 3 days and deconstruction will take about three times as much, or about nine working days (Cosper, 2000). However, the report did not specify the crew size. 4.5. Study no. 5 This is the NAHB pilot project described in previous sections (NAHB, 1997). A twostory, four-unit, 2000 SF residential building was deconstructed in 15 working days. The total labor hours were 902.5. This represents a deconstruction productivity of 0.45 h/SF. The labor crew consisted of five laborers and a foreman. Based on the case studies described above, the reported time to deconstruct a residential building of 1000–2000 SF ranges from 10 to 15 working days using a crew size of 5–6 workers (Table 7). Demolition of the same building may be completed in just one-fifth to one-third of the time required for deconstruction (The Air Force Center for Environmental Excellence, 2003; Cosper, 2000). The project duration for the 3600 SF building in Table 7 is only an estimate and the building was not actually deconstructed. The first three cases in Table 7 show that the duration to deconstruct a residential building is on average 7.4 working days per 1000 SF of building. This is the project duration estimated for building size of 1000–2000 SF and a crew size of five laborers. Deconstruction can potentially be completed in a timelier manner if a larger crew size or a more experienced crew is utilized.
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Table 8 Cost of deconstruction delay
Square foot (SF) Cost ($/SF)a (Means, 2002) Home office overhead rate (Means, 1998) (percentage of direct costs) Construction duration (weeks) Total overhead ($/SF) Overhead per week ($/SF/week) Deconstruction duration (weeks) Demolition durationd Delay due to deconstruction Effect of delay on cost ($/SF) (additional overhead) Average additional overhead ($/SF)
Average one-story
Average two-story
1600 77.52
1600 74.68
3400 60.82 7.70
26b 5.97 0.2296 2.4 0.6 1.8 0.41
3200 61.50 7.70
40c 4.68 0.1171 5.0 1.3 3.7 0.43 0.42
26b 5.75 0.2212 2.4 0.6 1.8 0.40
40c 4.74 0.1184 5.0 1.3 3.7 0.44 0.42
a
$/SF, cost adjusted by average location factor of 1.054 for Massachusetts (Means, 2002). Allen and Thallon (2002). c Estimate from local contractor. d Twenty-five percent of deconstruction duration, average from The Air Force Center for Environmental Excellence (2003) and Cosper (2000). b
5. Potential cost of deconstruction due to project duration Deconstruction, as discussed above, may lengthen the overall project duration as compared to demolition. To estimate the cost of this delay we took into account the contractor’s overhead costs during the delay period. Contractor’s weekly overhead is estimated using R.S. Means data and average construction duration. Multiplying this overhead cost by the potential delay due to deconstruction duration provides an estimate of the additional cost of deconstruction due to schedule delay. The average cost of deconstruction delay for one- and two-story, 1600–3400 SF, homes is estimated as $0.42/SF (Table 8). This is approximately 0.6% of the average total construction cost. Furthermore, for redevelopment projects there will be finance charges to the developer. These charges are not considered in our analysis because they vary widely by the project type and owner.
6. Summary and conclusion Similar conclusions are reached in our analyses based on the CCE study and the NAHB study. The adjusted cost analyses of the CCE and NAHB case studies using current Massachusetts’s cost data show that deconstruction is less favorable to total demolition. Our analyses suggest that in Massachusetts’s net deconstruction costs may vary between $10.21/SF and $15.53/SF, while demolition costs are estimated as between $8.15/SF and $13.25/SF. This shows deconstruction costs for Massachusetts could be 17% (adjusted from NAHB study) to 25% (adjusted from CCE study) higher than demolition costs.
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Table 9 Sensitivity of cost parameters in demolition and deconstruction Parameter
Net deconstruction cost Labor cost Disposal cost Salvage value Total demolition cost Disposal cost Demolition cost
Percentage change in Massachusetts net deconstruction or demolition costs due to a 1% change in parameter Based on CCE study
Based on NAHB study
0.89 0.10 −0.17
0.91 0.10 −0.13
0.44 0.39
0.65 0.24
Table 9 presents a summary of the potential effects of selected cost parameters on the overall deconstruction and demolition costs. As shown in Table 9, the sensitivities of cost parameters are consistent across the two studies used as the basis for our analysis for Massachusetts. For net deconstruction cost, the most sensitive cost parameter is the labor cost, followed by the salvage value, and lastly the disposal cost. For total demolition cost, the most sensitive parameter is the disposal cost for both studies. In each of our analyses for Massachusetts, we apply the productivity and waste generation rate reported in the CEE and NAHB studies. Deconstruction in Massachusetts will become more favorable if productivity increases or lower wage rate or higher disposal cost applies. While disposal cost and wage rate may be predominately controlled by the market, contractors may improve their deconstruction productivity through training, planning, and experience. Such experience-building practice is worth considering for contractors in the region where disposal cost is likely to continue to increase. The productivity in the NAHB study is much lower than that in the CEE study. The main cause is likely that the NAHB building had brick walls while none of the six buildings in the CCE study had bricks. The cost difference between deconstruction and demolition is even higher if the impact of extended project duration caused by deconstruction is considered. Residential deconstruction duration is estimated at 7.4 working days per 1000 SF with a crew of five laborers. We estimated the additional contractor overhead cost of deconstruction delay for one- and two-story, 1600–3400 SF, homes as $0.42/SF. When considering deconstruction, a building’s condition should be evaluated to see how much salvage could be recovered and a cost analysis similar to the one done in this report will provide a quick way to compare deconstruction and demolition costs. Deconstruction is also attractive when access to the site is limited because demolitions usually require larger space for equipment. In urban settings where the lack of space can slow down the demolition process, deconstruction may be a reasonable alternative. Future deconstruction studies should pay more attention to the time requirement compared to demolition especially on lands that are scheduled for immediate redevelopment. Deconstruction is most preferable to demolition when there is no such time constraint. Deconstruction represents an effective option for reducing C&D waste generation. Certain cost parameters associated with the deconstruction practice may vary among different regions. A comparative cost analysis can provide an insight as how each cost parameter
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may impact the overall costs. Such analysis can also help us identify the conditions under which deconstruction can be cost–effective. Our analyses suggest that both improved deconstruction productivity and increased waste disposal costs represent such opportunities. This study also demonstrates an approach for planners of regional waste management programs to evaluate and develop strategies for promoting C&D waste reduction.
References Allen E, Thallon R. Fundamentals of residential construction. New York, N.Y.: John Wiley and Sons Inc.; 2002. Bureau of Labor Statistics. 2001 metropolitan area occupational employment and wage estimates. Division of Occupational Employment Statistics, U.S. Department of Labor, Bureau of Labor Statistics; 2002, http://www.bls.gov/oes/2001/oes 1120.htm-b47-0000, last accessed April 7, 2003. Christoforou C. A systems analysis tool to assist decisions in construction and demolition waste management. M.S. Thesis. Boston, MA: Northeastern University; 2002. Cosper SD. Selection of demolition reduction, reuse, and reduction, reuse, and recycling methods recycling methods. Charlotte NRC, Charlotte, NC: Construction Engineering Research Laboratory’ NRC; 2000. Emmaus A. Taking the deconstruction road to C&D management. BioCycle 2001;42(5):42 [JG Press Inc.]. Executive Office of Environmental Affairs. Beyond 2000—solid waste master plan. Commonwealth of Massachusetts: Department of Environmental Protection; December 2000. Franklin Associates. Characterization of building-related construction and demolition debris in the United States. Report no. EPA530-R-98-010. EPA; June 1998. Guy B, McLendon S. Building deconstruction: reuse and recycling of building materials. Florida: Center for Construction and Environment, University of Florida; 2000. NAHB Research Center Inc. Deconstruction—building disassembly and material salvage: the Riverdale cast study. Maryland, MD: NAHB; 1997. Means RS. 1999 RS Means building construction cost data. 57th Annual ed. MA: RSMeans Company Inc.; 1998. Means RS. R.S. Means 1999 repair & remodeling cost data. MA: RSMeans Company Inc.; 1998. Means RS. 2002 RSMeans square foot costs. 23rd Annual ed. MA: RSMeans Company Inc.; 2001. The Air Force Center for Environmental Excellence. C&D waste management guide. Brooks AFB, San Antonio, Texas: The Air Force Center for Environmental Excellence; 2003, http://www.afcee.brooks. af.mil/green/resources/cdguide.exe, last accessed April 7, 2003.