Roof failure: Effect and cause

Building Operating Management, Apr 2003 by Warseck, Karen

STAYING OUT OF TROUBLE

Preventing problems begins with the design of the roof and choice of materials. The roof membrane chosen should reflect the characteristics of the building. For instance, if there will be a lot of foot traffic, the facility executive should plan on using a system that will be resistant to such damage. If the roof is wide open and there will be a great deal of thermal movement in the structure, a stretchable material such as an EPDM membrane is a better choice than a system that has limited elongation capabilities.

Details must be carefully thought out prior to installation. For example, a transition from a gravel stop to a parapet is a poor building design that must be compensated for in the roof design. A metal transition piece can help alleviate problems that occur as a result of differential movement and different directional movement between the gravel-stop portion and the parapet portion. Correcting slope-to-drain problems should be determined at the design stage.

Second, the roof must be properly installed. This means using dry materials and installing them according to the design details or manufacturer's requirements. Expansion joints have to terminate in a way that the end of the joint will still compensate for building movement. This means that there should be no material crossing the joint - not gravel stops, not copings, not membrane and certainly not roofing cement - that cannot flex or move with the movement of the structure. Seams should be adhered.

Finally, the roof must be maintained. Roof access should be limited to only those who need to be there. Keep smokers, lunches and sunbathers off the roof. Not only will the cigarettes burn holes in the membrane, the foot traffic will damage the surface and cause the roof to fail prematurely. Owners should monitor the activity of sign installers and window washers to be sure that they are not damaging the roof as they work. New HVAC installations should be flashed not by the mechanical contractor but by a competent roofing contractor to be sure that the penetrations are sealed.

The roof itself should he examined twice a year and drains cleared and roof debris removed. All small problems like punctures and sealant failures should be addressed at this time to be sure that they are not causing problems that will lead to failure. A roofs life is finite, but it doesn't have to be short lived. Some common sense when designing the roof, some attention to detail when installing it, and some care when using it will maximize its life.

BY KAREN WARSECK. CONTRIBUTING EDITOR

Contributing editor Karen Warseck, AIA, is president of Building Diagnostics Assoc., a Hollywood, Fla., architecture firm that specializes in building repair consulting.

E-mail comments to edward.sullivan@tradepress.com.