Contractors Prequalification for Roof Replacement
The MacDonald Building, located at 344 Edmonton Street is within the center of the city of Winnipeg. The building was constructed in 1960-1961 and has numerous renovations and modifications done over its lifespan. It is a four-story building with a basement/lower level and houses multiple government departments with its largest tenant being Transport Canada.
The roof membrane is original and nearing the end to its useful life. As the roof continues to age, frequency of roof leaks, damage and disruption to tenants increase. Replacement may provide opportunity to improve insulation values. Patching around the duct along roof was done in summer of 2013 as some leaks had developed in tenant space. BCR recommends replacing the built-up roof in 2013.
The scope of work associated with this option involves completely replacing all the roofing systems on the MacDonald Building, with a new 2-ply Modified Bitumen insulated roofing system. In addition, the new insulation will be sloped to provide positive drainage to the existing roof drains. This will limit the standing water on the roof and the therefore reduce the potential for leakage. Due to the increase in overall insulation thickness, some modification to the curb heights for mechanical units will be required. It is unlikely that any parapets will have to be extended due to increased insulation thickness. All roof drains will have to be extended with this option. These costs are included within the estimate. Roofs installed to the current National energy Code of Canada (2015) require an overall thermal transmittance of 0.162 W/(m2 K), equivalent to RSI 6.17 or R-35. Therefore, an R35 roof meets the requirements. The addition of a fully adhered vapor barrier will assist in the total performance of the new roof system, including a detailed membrane at all roof wall interfaces. The new roof system will meet and exceed the CSA123.21 roof assemblies for wind uplift.
