A turbine vent is the spinning cap on a round metal pipe that rises out of the roof and pulls hot air out of the attic. When one leaks, the water usually shows up as a stain on the ceiling directly below it, sometimes as a drip onto insulation you can see from the attic hatch. The stain tells you where the water is getting in, but not which part of the vent failed. A turbine has three parts that can each leak or wear out: the flange flashing that sits under and over the shingles, the neck or collar where the pipe passes through that flashing, and the rotating head with its bearing. Each one needs a different repair, so it is worth working out which one is failing before anyone quotes a price.
Leak and repair
Start in the attic on a rainy day or the morning after one. Bring a flashlight and look at the vent pipe from inside. Water running down the inside of the pipe or dripping from the collar means the neck is open to rain, usually because the collar seam has split or the head has been pushed off or cracked. Water that appears on the outside of the pipe and runs into the attic along its wall usually means the flange has let go, with nails pulled out of the deck or shingles above the flange lifting. A stain that is not directly under the vent but a few feet downslope points to water that ran across the deck from the flange before it dropped. The ceiling stain is a poor guide on its own, because the path water takes through the attic can be long.
Freeze and thaw cycles work on the collar seals every winter. The sealant or the seam at the base of the neck splits, and the rubber gaskets some turbines use age out under summer heat, which is hard on any roof in the St. Louis area. Hail season adds dents to the head and cracks to the cap, and those dents can crack the bearing housing so the head spins badly or stops. A turbine that squeaks, wobbles, or sits still in a light wind is worn, but a stopped turbine does not by itself let water in. It reduces the airflow the attic needs, and that can show up as hot upstairs rooms in July, which is a separate problem from the leak.
There are three repairs that match the three failures. If only the head is damaged and the base flashing is sound, replacing the turbine head is enough. If the flange is lifted, rusted at the edges, or held down by nails that have backed out, the base has to come out so the new flange can be lapped correctly. The upper edge of the flange should sit under the shingle course above it, and the lower edge should sit over the course below it, so water running down the roof passes over the metal instead of under it. A bead of sealant on a collar that is already split is a stopgap, the same way caulk is a stopgap on any roof penetration. It can hold for a while, but the water is still reaching the deck, and the wood under the flange is where the damage builds.
When the base is replaced, the crew should also look at the shingles on the uphill side and along the sides of the flange. Shingles that were nailed over a lifted flange are often cracked or have lost their seal, and they need to come out, not just be pressed back down. If the deck under the flange is wet or soft when it is opened, the rotted boards need to be cut back to sound wood and replaced before the new flange goes on. The crew can only make that call once the old flange is up, so ask the question before the work starts.
What it costs
The price of a turbine repair depends on which part has to change and how much roof has to come off to reach it. Replacing a head on a low, easy roof is a short job. Replacing the base on a steep slope, with shingles to lift and reset around the flange and a few deck boards to cut out, is a different invoice. A quote that only says fix the vent, with no line for the flange, the shingles, or the deck, is not yet a price you can compare. Ask the roofer to split the work into the head, the base, the shingle work, and any deck repair, because those lines show what each part costs and what you would pay for if the deck turns out to be wet.
Ask whether the quote includes the new flashing material and the sealant, or whether those are assumed. Turbine heads come in several diameters, and a head one size too small will not move the air the attic needs, so the size should be written into the scope along with the make if the vent is being replaced. If the vent is being moved or a second one is being added, that is new work and should be priced as new work, not folded into the repair.
What to ask
- Which part is failing, and what did you see on the deck, the flange, and the collar when you opened it up?
- Will the flange be lapped so the upper edge sits under the shingles and the lower edge sits over them, and will you show me the lap in a photo before the new shingles go on?
- Will the old flange be removed completely, or only covered?
- If the deck under the flange is soft, how many boards will you cut back, and what does each board cost?
- Will the shingles disturbed around the vent be replaced, or only resealed?
- Will you photograph the vent, the flange, and the deck before and after the work, and give me those photos with a written scope?
- Who comes back to check the attic after the next heavy rain?
If hail damaged the vent head or the flashing, Keys documents the damage, puts a written scope with photos and measurements in your hands, and attends as the contractor while you deal with your own insurer. Missouri law under RSMo 407.725 forbids a roofing contractor from representing or negotiating your insurance claim, and from saying anything about paying, waiving, or covering your deductible. Keep the claim conversation with your insurer and the repair conversation with the roofer. To schedule a turbine inspection, call Keys at (314) 220-2333.