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August 24, 2020 - 20 min

Increasing the Durability of a Roofing System Through Resurfacing

Published by Pierre-André Lebeuf

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Durability

Whether environmental (such as weather conditions), social (such as undesirable use of the building) or economic (such as lack of maintenance), several factors can influence the service life of a structure.

Literature reveals that 70% of the buildings can reach the age of 51 to 100 years before being demolished, that is to say 13% will reach 100 years or more, 38% will stand for 76 to 100 years, and 19% will last for 51 to 75 years [1]. Also, almost 50% of solid waste comes from construction materials [2]. In addition, 60% of the raw materials extracted from the lithosphere are used for the construction of civil engineering works (20%) and buildings (40%) [3].

All things considered, these figures show that the service life of buildings is relatively long, spanning several decades. However, they also reveal a high consumption of raw materials to manufacture construction materials and considerable waste in terms of residual materials generated when the materials reach the end of their useful life.

Resurfacing

The overall cost of a building can be optimized by choosing suitable technical solutions at its design phase. In the case of a roofing system, this choice can contribute to the durability of the structure while delaying the replacement of all of its components.

One of the solutions is resurfacing, and this solution has been offered by SOPREMA for more than 20 years.

Whether heat-sealed or self-adhered, resurfacing involves installing a new cap sheet membrane over the existing waterproofing [4].

Case Study: CF Champlain in Dieppe (Nb)

All rights reserved Julian Parkinson.

The developer Cadillac Fairview, the firm WSP and the manufacturer SOPREMA selected resurfacing to ensure the durability of the 175,500 ft2 roof system of the CF Champlain shopping centre in Dieppe (NB). Built in 1974, the old roofing system (asphalt-gravel) was completely rehabilitated, giving way to a system with SBS membranes in 1999. Carried out in four phases (2019 to 2022), the resurfacing works offer significant benefits compared to the complete reconstruction of the roof system.

Read this case study to see how the environmental impacts were reduced and the economic benefits acquired during this large-scale project.

Project Collaborators

  • Developer: Cadillac Fairview
  • Contractor (roofer): A-Tech Roofing Ltd.
  • Consultant: WSP Global Inc.
  • SOPREMA sales representative : Daniel Robichaud

Project Description

Environmental Impacts

Mitigated and avoided environmental impacts could be estimated by comparing the quantity of materials required for a complete roof repair and the one required for a resurfacing. The impacts measured relate to the lifespan of the system as well as to the consumption of raw materials and energy.

All rights reserved Julian Parkinson.

Note: Typically, only one ply of membrane is required for a resurfacing over an existing membrane. For this specific project, the consultant/ownerchose to install a two-ply membrane over the existing system. 

Between 25 to 95 Years Gained

The old roofing system (asphalt-gravel) was 25 years old when it was first repaired in 1999, that is to say when it was replaced by the new system (SBS membrane). Although the lifespan of the materials that were to be replaced generally varies from 25 to 30 years, the developer decided to be proactive and perform the first resurfacing after 20 years in 2019.

Compared to a complete repair, the first resurfacing extended the life of the cap sheet membrane installed over the existing waterproofing by at least 25 years. In doing so, there was therefore no need to replace the roofing system’s underlayments, namely the vapour barrier, insulation, support panel and two-ply system.

As part of this project, two other resurfacings would be possible in the future. These potential works would extend the life of the existing system by 50 years. Considering that it is already 20 years old and another 25 years was added with the first resurfacing in 2019, this would mean that the roof system could reach a lifespan of 95 years*.

One of the solutions is resurfacing, and this solution has been offered by SOPREMA for more than 20 years.

Durability of the Roofing System Depending on the Different Types of Work (in Years)

* Although the frequency of work and the number of resurfacings are at the discretion of the customer, it is likely that the physical integrity of the cap sheet membrane will be greater than that covered by the selected warranty. The number of resurfacings is also determined by the estimated capacity of the building structure. The physical integrity of the roofing system materials can influence the frequency and nature of the work. The roofing systems offered by SOPREMA allow up to three resurfacings.

Raw Material Reduced by 31%

Consumption of Raw Materials for the Production of Materials by Type of Work (in Metric Tonnes)

Compared to a complete repair, resurfacing reduced the quantity of raw materials normally needed to manufacture construction materials by 31%. The complete repair would have required 84.56 metric tonnes of material compared to resurfacing, which was completed with 58.59 metric tonnes. Hence, 25.97 metric tonnes of materials were saved.

For the whole project, the complete repair would have generated about 240 metric tons of residual materials, which is more than 160 containers of avoided waste*.

* This number was estimated by the roofer (A-Tech Roofing Ltd.). One container has a capacity of 40 cubic yards (20 ft × 8 ft × 8 ft).

All rights reserved Julian Parkinson.

Greenhouse Gases Reduced by 67%

Compared to a complete repair, resurfacing should have reduced greenhouse gas (GHG) emissions associated with the production and transport of materials to the site by 67%. The complete repair would have totalled 11.25 tonnes of CO2-eq compared to 3.72 for resurfacing, which is a 7.53 tonnes of CO2-eq difference.

The avoided GHG emissions amount to 7.14 tonnes of CO2-eq (-68%) for the production and 3.84 tonnes of CO2-eq (-52%) for transportation. It should be mentioned that only 5 shipments of 53-foot trucks were needed for the resurfacing, whereas the complete repair would have required 25 shipments. This represents a total of 18,000 km of travel avoided. All in all, although the results may vary depending on the construction project characteristics, the case study reveals that resurfacing can significantly mitigate, delay or even avoid some environmental impacts. Being a form of reduction at the source, it is a simple solution that also increases the durability of the structure.

 

Total Greenhouse Gas (GHG) Emissions Depending on the Type of Work (in Tonnes of CO2-eq.)

* The estimate of GHG emissions is based on the following parameters and sources: Environment Canada, 2019. National Inventory Report 1990–2017. | Environment Canada, 2017. National Inventory Report 1990–2015. | IPCC, 2006. Guidelines for National Greenhouse Gas Inventories, Volume 5: Waste, Chapter 4: Biological treatment of solid waste.

The estimate of GHG emissions includes the following activities and sources:

  • Production: Scope 1 – Emissions directly related to installations – Combustion of natural gas – Combustion of propane – Combustion of fuel oil. Scope 2 – Emissions indirectly related to energy – Electricity consumption. Scope 3 – Other emissions indirectly related to residual materials. tCO2-eq/product surface.
  • Transport: Scope 1 – Emissions directly related to transportation – Diesel – Heavy vehicle – Moderately efficient system – Flatbed. Weight-distance (e.g. freight transport).

Economic Gains

Comparing the complete repair of the roof with the resurfacing allowed estimation of the savings generated when purchasing materials as well as the time saved during the works. 

All in all, although the results may vary depending on the construction project characteristics, the case study reveals that resurfacing can significantly reduce the time required to complete the work on site and, at the same time, reduce the cost of purchasing materials.

Reduction of Material Costs by 45% To 50%

Compared to a complete repair, resurfacing has reduced the purchase costs of new materials by 45% to 50%. This creates considerable savings, especially in the long term depending on the frequency and number of resurfacings required.

Reduction of Time on Site by 35%

Compared to a complete repair, the resurfacing has reduced the time required to complete the work on site by approximately 35%. The resurfacing work lasted 26 weeks whereas the complete repairs would have required 40 weeks.

 

Duration of the Work Depending on the Type of Work (Weekdays)
References

[1]  The Athena Institute (2004). Minnesota Demolition Survey: Phase-Two Report.

[2] Transparency Market Research (2017). Construction Waste Market – Global Industry Analysis, Size, Share, Growth, Trends, and Forecast 2017–2025.

[3] Zabalza Bribián, I., Capilla, A. V., Usón, A. A. (2011). Life-cycle Assessment of Building Materials: Comparative Analysis of Energy and Environmental Impacts and Evaluation of the Eco-efficiency Improvement Potential. Building and Environment, 46(5), pp. 1133–1140.

[4] SOPREMA (2016). Repair and Re-Cover Roofing Guide.