By building type
A restaurant roof is a chemistry problem before it is a roofing problem
A restaurant has one of the smallest commercial roofs and one of the most demanding. It is crowded with equipment, it is coated in something that attacks roofing materials, and it sits directly above a business that cannot afford to close.
The grease problem
Kitchen exhaust carries vaporized fats that condense on the roof around the fan. Rain spreads them outward. On a membrane that is not formulated for it, the result is softening, discoloration and eventual failure in a widening circle around the exhaust, while the rest of the roof looks fine. It is one of the most recognizable failure patterns in commercial roofing.
- Specify PVC over the kitchen, which is formulated to resist the exposure.
- Fit and maintain grease containment at every cooking exhaust fan. The maintenance is the part that gets forgotten.
- Keep drains clear of grease, because grease plus debris blocks a drain faster than debris alone and a blocked drain on a small roof floods quickly.
- Protect the walking routes, since a greasy membrane is genuinely slippery and the exhaust fans are exactly where people have to go to service them.
The drawing below shows the welded PVC lap that goes over a kitchen, with the three membranes that do not suit the exposure drawn alongside it.
Everything else that is on a restaurant roof
Make-up air units, condensers, the grease exhaust, gas lines on blocks, condensate lines, and often a walk-in cooler unit — on a roof that might be a fraction of the size of a warehouse bay. Nearly every leak is at one of those curbs or supports rather than in the field, and nearly every one of them has been serviced by somebody who did not repair the membrane afterwards.
| Component | What goes wrong | What it needs |
|---|---|---|
| Grease exhaust fan curb | Grease saturation and a failed flashing under the fan | Correct membrane, containment, and flashing that can be inspected |
| Gas lines on blocks | Blocks migrate and abrade the membrane; nobody flashes them | Proper supports with a bearing pad, not a paver on the membrane |
| Condensate discharge | Constant wet area, algae, and freeze damage in winter | Piped to a drain rather than discharged onto the roof |
| Unit service hatches | Membrane damage from tools and foot traffic | Walkway pads on the route, and a rule about who goes up |
Working around the kitchen
- Work usually happens overnight, on a closed day, or in the window between service and prep.
- Odor is the constraint that surprises people. Adhesives and hot asphalt smell, and the smell finds its way into a kitchen and dining room through make-up air. Self-adhered and mechanically attached systems avoid most of it.
- Open flame over a restaurant is a serious decision and often simply the wrong method for the building.
- Anything that requires the exhaust fans to be off has to be sequenced with the kitchen rather than announced to it.
Membrane failing in a circle around the kitchen exhaust?
Talk to us about the buildingCan just the greasy section be replaced?
Often yes, as a sectional replacement in a compatible membrane with proper transitions and containment fitted at the same time. It buys real time, and it is worth being clear that the surrounding roof continues to age on its own schedule.
How quickly does grease damage a roof?
It depends on the volume of cooking, the exhaust design and whether containment is in place. What is consistent is that it is progressive and concentric, so a roof with a visibly affected ring around the fan has an established problem rather than a new one.
Can you work while we are open?
Some scopes can be done in sections without affecting service. Anything noisy, smelly or directly over the dining room usually cannot, and it is better to plan around that than to try.
Do you deal with the exhaust fan itself?
The roofing scope covers the curb and the flashing around it. The fan, the ductwork and the hood cleaning belong to the kitchen exhaust trade, and the two have to coordinate where the curb is being rebuilt.
All work is performed by licensed and insured local roofing professionals.