26 September 2006
New Trusses and Decking.
Adding lightweight steel or wood trusses or rafters and a nailable deck permits
the use of most conventional steep roofing systems.
Re-roofing invariably means disruption of building operations. For some
sensitive occupancies (e.g., top floor computer rooms, surgical suites,
laboratories, or telephone equipment) a total tear-off may be an unacceptable
risk. The addition of a secondary membrane should be analyzed for
A complete tear-off requires good weather since the building is usually occupied
and nightly tie-offs may not provide adequate protection. The demands of
protecting the building may prompt phased construction--especially when a
thicker insulation system is being added and it is not feasible to run from eave to
ridge in a single day.
Nightly Seal-off of New Penetrations.
When new structural members are added it is necessary to carefully seal where
the new anchor bolts penetrate the old roof system. This seal might be little
more than asphalt mastic or it may be more complex. Existing drains must
remain in working order until the new roof and associated drainage system is
Adding new insulation and/or an air space above the existing roof will change
snow-melting characteristics. Generally the added insulation reduces vapor
condensation problems; however, the effect of the new insulation on vapor
Planning a re-roofing project must include all the logistics of the project,
especially if the re-roofing occurs over an occupied building. Items to consider in
the planning include the following:
a. Protecting the newly applied roof covering from tear-off debris and
construction traffic. This is critical to the longevity of the new roof;
b. Planning for the possible presence of asbestos-bearing materials
and landfill or recycling rules and regulations that may require
separation of construction materials;