A plumbing vent is the pipe that rises through your roof so sewer gas can leave the house and air can reach the drain lines. On many St. Louis houses the top of that pipe is fitted with a plastic cap, often a hollow dome or a flared hood, and hail hits it the same way it hits everything else up there. The cap can crack, split at a seam or get knocked loose. It is a small part, and it is easy to skip when you are photographing a storm. That is why it belongs in the file.
Storm and hail
A plastic cap sits above the roof surface, so a walk around the lawn with a phone will not show you much of it. The damage often looks like a hairline crack on a dark dome, which is hard to see from the ground. From a ladder it is easy to dismiss unless someone is looking for it on purpose. Hail that hits the windward slope usually leaves the heavier marks there, so the stacks on that side of the house deserve a closer look than the ones on the far side.
An open or broken cap lets rain fall straight down the pipe. Water running down the stack reaches the rubber or neoprene boot where the pipe passes through the roof deck. If that boot is already aging, water can work past it into the attic, or travel along the pipe to the ceiling below. Debris can also drop into the stack. When water sits in the pipe top during a freeze, it can expand and split the cap a little further in the next cold snap. That is the freeze and thaw cycle working on a part that was already damaged. None of this means the whole roof has failed. It means an opening that was supposed to be protected is no longer doing its job.
The attic side of the stack is worth a look on the same day. Stand under each pipe where it comes through the ceiling and check the drywall around it for rings, soft spots or paint that has lifted. Check the insulation near the pipe for dampness or matted spots. A stain on the ceiling by a vent pipe does not prove the cap is the cause, but it tells you which stack to examine first from the roof.
What to photograph on the vent stack
Photograph each vent stack from the ground first, then from the roof if a crew is up there. Get the whole stack in one frame, with the roof slope behind it and a tape measure or a known object for scale. Then move in close enough to show the cap material and any crack, split, dent or missing piece. Shoot the boot at the base of the pipe too, because the boot is where water goes next. If the pipe is cast iron, look at the top edge for dents and check whether the cap is cracked, bent or pulled off its seat. Write down which slope each stack sits on, so the photos can be matched to a location later.
Do the same for any other pipe or vent that projects through the roof, including a bathroom fan cap, a dryer vent hood and a kitchen exhaust. The range hood and bathroom fan each have their own page on this site, but they belong in the same folder as the plumbing stacks. Keep the original photo files with their date information. A screenshot of a photo loses that detail, and it can be hard to show later when and where each picture was taken.
What it costs
A cracked plastic cap is usually replaced rather than patched. A patch on a cap that has already split tends to crack again along the same seam, and a new cap is a small part of the job. A cast iron stack with a dented top is a different case, because the pipe itself may need to be replaced or fitted with a new cap that seats properly. The boot under the cap should be checked during the same visit. If the boot is cracked or its flange has lifted, replacing only the cap leaves the water path open.
Ask for the cap and the boot as separate lines on the proposal, with the work described for each. A line that says vent work does not tell you what is being replaced, what material is going in, or whether the boot was looked at. A cap is usually a small part of the total, so the cost to watch is the trip itself. If the roofer is already on the roof for shingles, the vent work should be written into that same scope, not added later as a separate return visit with its own charge.
Keys Roofing documents this kind of damage with a written scope, photos and measurements, and the homeowner keeps those in hand. If you are dealing with an insurer, that conversation belongs to you and your insurer. Missouri law bars a roofing contractor from representing or negotiating a homeowner's insurance claim, and from saying anything about paying, waiving or covering a deductible. A roofer can document the damage and attend as the contractor, while the claim stays with the homeowner.
What to ask
- Will the crew photograph each vent cap and boot before touching it, and will those photos be attached to the written scope?
- Is the cap replaced in the same material, or does the proposal name a different cap? If it is different, is the reason written down?
- If the stack is cast iron, who checks the top of the pipe, and what happens if it has to be replaced?
- Is the boot under the cap replaced at the same visit, and does the proposal list it as a separate line?
- If the cap splits again over the winter, who comes back to look at it, and is that written down?
A good answer to each of these is short and specific. A roofer who says the vents will be looked at when the crew gets to them has not yet told you what will be looked at. Ask for the answer in writing before the schedule is set.
To have Keys look at the vent stacks on your roof, call the office at (314) 220-2333. Bring the photos you took from the ground, and note which stacks showed staining in the attic. That gives the crew a clear list to start from when they reach the roof.