On a flat or low-slope section, a stain near the ceiling drain or a wet patch by the scupper can make the whole membrane look suspect. Most of the time the fault is one small piece: the drain bowl, the clamping ring that holds the membrane to the drain body, or the seam where the membrane meets the flange. Water collects around a drain because it has nowhere else to go, so it presses on the weakest joint every time it rains.
Leak and repair
Find where the water stands
Start with what the water does after a storm. Ponding means water stays on the roof for a day or more after rain stops. Walk the flat section the morning after a heavy rain and look for the low point. If the standing water sits over the drain, the bowl, strainer dome and clamping ring are the first parts to check. Look for leaves, grit and roofing debris packed into the bowl, a cracked dome, and any gap between the ring and the membrane.
The clamping ring is a metal collar that squeezes the membrane against the drain body. Years of thermal movement loosen its bolts, and the membrane can pull up at one side. Water then runs under the membrane instead of across the bowl. The stain often appears several feet from the drain, because water travels along the deck or a joist before it drips through the ceiling.
Why it returns each spring
Freeze and thaw matter here. St. Louis winters fill drain bowls with ice, and a bowl that holds ice holds meltwater for longer. When the thaw comes, a partly blocked drain sends a second pulse of water onto the membrane. A stain that shows each March and fades by June points to a repeating path, not a single bad storm, and it usually means the drain edge has been moving with the seasons.
What a repair usually involves
Repairs fall into a few groups. The simplest is clearing the bowl and setting the strainer back in place. The next is tightening or replacing the clamping ring and bowl, then sealing the membrane edge to the flange with a compatible sealant or a membrane patch. If the membrane around the drain is cracked, blistered, or has lost its surface, a patch may hold for a season but will not repair the field of the roof around it.
Old repairs stacked on top of each other are common on drains. A drain that has been caulked three times usually has a membrane edge that was never reset. At that point the sound repair is to lift the membrane at the drain, reset it onto a solid flange, and seal it again. That is more work than a patch, and the written scope should say so.
Check the scupper and the edge too
A second common source sits at a scupper or the roof edge. A clogged scupper backs water up under the metal edge, and the water can come through the wall flashing or the top of the fascia. That is a different fault from a drain problem, so a roofer who checks only the drain has not finished the job. Ask the crew to look at both on the same visit, and ask for photos of each.
What it costs
Price depends on what has to be opened. Clearing a drain and resetting a strainer is a small trip. Replacing a clamping ring and bowl on one drain is a modest repair, often priced per drain. Patching the membrane around a drain is priced by area and by the number of layers involved. Lifting and resetting the membrane around a drain, with the surrounding field opened, costs more and should appear as its own line.
A usable written bid for a drain repair lists each item separately:
- Clearing debris, resetting the strainer, and a dated photo set of the pond
- Replacing the bowl or clamping ring, with the size and material named
- Membrane patch or edge seal, with the sealant or membrane product and the area stated
- Lifting and resetting the membrane at the drain, priced as a separate line
- A recheck of the drain after the next heavy rain, with the result in writing
A cheaper total is not always the right bid. A bid that says repair drain without naming the bowl, the ring, or the sealant leaves the scope open to whatever the crew finds once the section is uncovered. That gap often shows up as a change order after the work has started.
What to ask
Ask each roofer these questions before you agree to a scope.
- Where does the water stand after rain, and how long does it sit? Ask for a photo of the pond.
- Is the clamping ring loose on one side, and does the membrane lift at that edge?
- What drain bowl and clamping ring will be installed, by size and material?
- Will the crew check the scupper or edge on the same visit?
- Will the written scope include photos and measurements of the drain area?
- If the stain returns after the next heavy rain, who comes back, and how is that visit written into the contract?
Keys works as the contractor on the roof. The written scope comes with photos and measurements in your hands, and the crew attends the inspection to explain the repair. Keys does not handle, file or negotiate any insurance matter for you.
Before you call
Note the date of each stain, the weather in the two days before it, and whether the ceiling below is dry now. Note whether the ponding lasts after a light rain or only after a heavy one. Those notes shorten the visit. If you can photograph the drain from a window or the roof edge on a day when the water is standing, do that, but do not walk the membrane yourself, because a wet membrane tears and hides its seams.
Call Keys at (314) 220-2333 to set a time for a drain check on the flat section. Ask for the visit to cover the drain, the scupper and the edge in one pass, and ask that the written scope list each one. A dry day works better for the check, because wet membrane hides seams and lifted edges are hard to see.