A gas water heater in a Ladue basement often sends its exhaust out through the roof, and the metal pipe that carries it is one of the first penetrations a replacement disturbs. The pipe rises through the attic, passes through the roof deck, and ends in a cap above the shingles. Where it meets the roof, two parts do the sealing: a flashing that lies on the roofing, and a storm collar that closes the gap between the flashing and the pipe. When the old shingles come off, both parts come up with them. What goes back on decides whether the new roof stays dry at that spot for the next several years.
This page is for the homeowner who has a roof quote in hand and wants to know whether the water heater flue is written into it. Often it is not. A roof bid speaks in squares, nails and underlayment, and a flue collar shows up only if someone counts it as a line. Ask before you sign, and ask in a way that makes the answer specific.
Why the flue is a roof detail, not only a plumbing detail
The flue is built to carry combustion gases up and away from the house. For the roof, it is simply a hole that has to be made watertight while staying clear of the pipe's heat. Warm exhaust moves up through the pipe, and in a cold attic, especially on a January night when the attic air is far below the temperature inside the flue, moisture can condense on the cold outer surfaces of the pipe. That condensation drips back down and shows up as a stain on the attic sheathing or the insulation near the pipe.
A roof flashed badly at the pipe will leave a stain of the same shape, from water that came in from above instead of condensing below. From the attic the two look almost identical. The difference shows at the flashing, where a roofer can see whether the water was running down the pipe from the cap or seeping through a joint that was never sealed. That is why the flue belongs in the roof scope, and why the roofer, not the plumber, is the one who can confirm the seal.
The four lines a written scope should name
- The flashing at each pipe, with the material named and a note on whether it is new or reused.
- The storm collar or boot at each pipe, and whether it is replaced rather than reset.
- The cap or termination above the roof, and who sets it back on the pipe.
- The height of the cap above the shingles, checked against the manufacturer's instructions for the installed unit and the local code.
Reusing an old flashing is sometimes reasonable on a pipe that is sound and not corroded, but a reused flashing should appear in the scope as a choice, not turn up as a surprise on the day of the work. A collar that has cracked or lost its seal under the old shingles is usually inexpensive to replace while the roof is open. Discovering it after the new shingles are down means lifting courses to reach it.
What a failed collar looks like from the ladder
A collar that has lost its seal often shows a dark band on the metal where water has run down, or a gap where the collar meets the pipe. Rust streaks below the cap are another sign, as is a crust of old sealant that has cracked and pulled away from the pipe. Ask the roofer to photograph each one at the start of the job. Those photos are useful later if a leak appears near the pipe, because they show what the crew found before the new roof went on.
What the range hood and bathroom fans add to the list
Many Ladue kitchens have a range hood that vents outside, and bathroom or laundry fans often finish at a cap in the roof or a wall. Each of these is another pipe or duct passing through the same roof surface. A range hood cap at the roof is commonly a small sheet metal piece with a flange that lies under the shingles above it and over the flashing below. If that cap is left off the bid, it tends to get the least attention when the crew is busy and the weather is turning.
The question to ask is simple: how many penetrations does the roof have, and is each one a line in the scope? A roofer who counts the water heater flue, the range hood, the bathroom fan and the dryer vent as separate items is describing the work honestly. A roofer who writes penetrations included without listing them is leaving the scope open to argument later.
Freeze and thaw at the collar
St. Louis winters run through repeated freeze and thaw cycles, and each cycle can work water into any joint that is not properly sealed. A storm collar that is caulked alone, without a proper flashing beneath it, tends to fail first at the top edge, where water sheds from the shingles above. Once that happens, the water runs down the outside of the pipe and into the attic at the flashing line. The fix is not more caulk on top. The fix is a flashing that sheds water over the shingles and a collar that is fastened and sealed as a unit.
Ask whether the crew will fasten the flashing according to the manufacturer's detail and whether the collar will be sealed at its base, not only at the top. Those are practical questions that a roofer should answer in a sentence without reaching for the manual.
Where the permit desk comes in
Most St. Louis County municipalities require a permit for a roof replacement, and each city sets its own permit scope and inspection points. The desk that covers your address is the one that decides whether a replaced flue cap or collar needs to be looked at separately. Call that desk before the permit is pulled and ask whether penetrations that carry combustion exhaust are part of the inspection. Do not assume the roofer already knows the local answer, because the answer varies from one municipality to the next.
It also helps to ask the roofer which desk they pull from and whether they schedule the inspector for the day the penetrations are open. A roof inspection that happens after the shingles are fully down cannot see the flashing beneath them, so the timing of the inspection matters as much as the scope itself.
Questions to put to the roofer
- Which flashing and collar will be installed at the water heater flue, and is it new or reused?
- Who sets the cap back on the pipe, and at what height above the finished shingles?
- Is the range hood cap and each bathroom or laundry fan cap listed in the scope, with its own flashing?
- Will the crew photograph each penetration before the shingles go back over it?
- Which permit desk do you pull from, and when is the inspector scheduled relative to the penetrations?
A roofer who answers these questions in plain words is describing the work that will happen on your roof. One who says the penetrations are included without naming them has not yet decided what the job includes. Ask for the answers in writing before the start date is set, and keep a copy with the rest of the bid.
What to check before the tear-off starts
Walk the attic with a flashlight the day before the crew arrives. Look at each pipe where it leaves the ceiling plane and note any staining on the sheathing, rust on the pipe, or a gap at the collar. Take a phone photo of each one. This takes about ten minutes and gives you a baseline, so that a new stain after the work can be traced to the right place. If you see something that concerns you, tell the roofer before the tear-off begins rather than after the new roof is closed.
If you want the penetrations walked with a crew before the bid is final, Keys Roofing can be reached at (314) 220-2333. Keys documents the flues, collars and caps on the roof and puts a written scope with photos and measurements in your hands, so the decision about each pipe is yours to make with the details in front of you.