Membranes vs Coatings for Roof Overlays

When you start experiencing leaks with a flat roof and need to start thinking about replacements, there are many different options available. For the money conscious consumer, a roof overlay or a roof coating directly to the existing roof membrane may seem like an attractive option, however, before going this route, you must consider the following criteria:

Coatings work when:
•    There is no moisture in the roof assembly
•    The existing membrane is clean and free of dust, dirt, oils, ponding water, etc.
•    There are no blisters, ridges, splits, etc.
•    When installed by a manufacturer certified contractor, using the correct products and following manufacturer’s guidelines

Membranes work when:
•    There is no moisture in the roof assembly
•    The existing membrane is clean and free of dust, dirt, oils, ponding water, etc.
•    There are no blisters, ridges, splits, etc.
•    When installed by a manufacturer certified contractor, using the correct products and following manufacturer’s guidelines

If your roof has been leaking for an extended period of time, it is recommended that you go the full replacement route. In this case, we’ve found that coatings are not a good substitute for a membrane replacement.

Those lucky enough to have a roof that is in relatively good condition and are able to do an overlay option, the type of roof and environment in question can influence the type of roof overlay you choose. If you have a small roof with a lot of accessories, details or tight spaces and not a lot of space for ground set-up, coatings may be the solution for you. If you’re in a fire prone area or are concerned about the smell of asphalt, coatings require no open flame and some of the rubberized roof coatings have no VOCs. If you have a large open roof, membranes may be your best bet. Membranes also tend to be stronger and more puncture resistant. Both options when used as an overlay can reduce waste sent to landfill sites.

If the existing roof membrane is in poor condition with many ridges, blisters, cracks, and moisture laden insulation, it will require restoration of these areas prior to a roof overlay in order for the new membrane to perform well. To determine the extent of moisture in the insulation requires an engineer report and thermographic roof scan. This can be very costly and can often take months to complete as the roof scan must be done in optimal conditions. We often find in aged roofs that it is more economical to consider a full roof replacement if your roof is in this condition as roof restorations are very labour intensive and costly.