Flat Roofing done right.

A flat or very-low-pitch roof needs its own approach, and the first question I ask is how long you plan to keep the building. Owners of commercial buildings they will hold for a long time usually want the best option: a full tear-off to the bare deck, repair any decking, wood or metal, then insulation board, membrane and drip edge. With a concrete deck there is usually no damage on the outside, but if it has been leaking for a while there can be damage on the inside.

There are four ways to do it, and we price them side by side. A roof-over leaves the existing covering in place, if its condition allows, and adds a new membrane and drip edge on top. A roof-over with insulation puts about two inches of ISO board over the old roof first, then drip edge and membrane. A partial re-roof takes off all the membrane, tears out only the insulation that is wet or damaged, spot repairs, and lays new membrane. And the full tear-off, down to the deck. On commercial roofs the membrane is 60 mil TPO.

Coatings have a place, and it is a narrow one. A coating fits a roof that is getting toward the end of its life with only minor wear and damage, where we can patch the weak spots and coat over the whole thing. It does not fit a roof that has leaked for a long time and now holds water. Once there is ponding, a coating is not the answer, and I will say so.

Flat sections on houses, a lanai roof or an addition, are a different job and an easier one. They get base and cap modified bitumen. If the area is truly flat with no pitch at all, a tapered insulation system goes on first. In plain terms that is material that builds a slope where the roof never had one, with a little insulation value as a bonus, so water leaves instead of sitting. If the area already drains, it is not needed and base and cap goes straight on.