Attic Air Sealing Is Often Left Out of the Reroof Price

A reroof is one of the few times a St. Louis homeowner can reach the attic floor without tearing into the ceiling. The crew will be up there anyway to pull the old shingles and check the decking, so sealing air leaks at the top of the house costs less during a reroof than it would as a separate job next year. Most reroof quotes do not mention it. That silence is worth a question, because a new roof over an attic that still leaks warm, wet air can hide a problem that shows up a few winters later.

Where the air gets in

Warm air rises. In a St. Louis winter, the air inside a heated house is warmer and wetter than the air in the attic, and it finds every gap between the living space and the attic. The usual routes are the top plates of interior walls, the openings around plumbing stacks, the chase around a chimney, the recessed lights in the ceiling, bathroom and kitchen exhaust fans that end in the attic instead of outside, and the attic hatch itself. Each of these lets moist air rise into the cold space under the roof deck.

When that moist air meets the underside of the cold sheathing, it condenses. In January the condensation can freeze into frost on the nails. In a warm spell it drips, and the wood stays damp. Over a few winters the decking can soften near the eave, and staining shows up on the rafters before anyone sees it from inside the house. A new shingle does not stop this, because the problem sits below the shingle.

Air leakage also feeds ice damming at the eave. Heat from the attic warms the roof deck above the top of the wall, snow melts on that warm patch, and the water runs down until it reaches the overhang, where it refreezes. Better ice protection at the eave helps the outer edge, but if warm air keeps reaching the deck, the melt starts again on the next cold day. Ask whether the sealing and the eave detail are being treated as one job, since each one affects the other.

Why a reroof is the moment to price it

The roofing crew removes the old shingles, and the decking stays exposed for a day or two. That is when the underside of the deck is easiest to reach from above and when the attic is open to the sky. Sealing from the top is slower and more limited. Once the new shingles are on, the work has to be done from inside, with a ladder through the attic hatch and a trade that may not be your roofer at all.

There is also a sequence question. Air sealing should happen before new insulation goes down, because insulation laid over open gaps does less than its rating suggests. If the roofer is not doing the sealing, you need an insulation or air-sealing contractor scheduled before the blown insulation goes in, which means two trades working in the attic on different days. Ask who is doing the work, when they arrive, and whether your roofing schedule waits for them or ignores them.

What it can cost, and what to ask for

Attic air sealing is usually priced from the number of penetrations, the length of the top plates, and the amount of foam or caulk the job needs. A small ranch with a few plumbing stacks and two bath fans is a different job from a two-story house with a finished attic and a chimney chase. No single number fits every St. Louis house, and any figure you read online is a range built from someone else's attic. What you can do is ask the roofer to show the line.

Ask for these items in writing, in plain terms:

• Whether air sealing at the attic floor is in the roof scope, and if it is not, who is responsible for it and when they arrive.
• The count or length the price is based on, such as the number of penetrations, linear feet of top plate, or the number of recessed fixtures.
• The sealing material by name, such as caulk, spray foam, or foam board, because each one costs a different amount and holds up differently in a hot attic.
• Whether the bath fan ducts will be routed to the outside, and whether that work is in the price.
• Whether insulation top-up is included or priced separately, and the depth it will reach.
• Whether the attic hatch will be weather-stripped and insulated, since it is a large opening in many houses.

A line that reads "air sealing, allowance" with no count underneath is a number that can move after the work starts. The same goes for a line that says "attic work included" without saying what that means. Ask the roofer to write the count and the material next to the price, so you can check it against what gets done.

Check the bath fans first

Bathroom and kitchen exhaust fans that vent into the attic are a cost that often goes unbudgeted. The fix is a duct to an exterior wall or a roof cap, and that duct has to be sized, sloped, and sealed where it passes through the attic floor. On a reroof, the roofer is already cutting the roof, so a fan that exits through the roof can be redone at the same time, if it appears in the quote. Ask whether the fan vent is being replaced as part of the new flashing, and whether the new cap is named in the bid. These are small lines, but they tend to disappear when a quote is trimmed to hit a number.

What a complete quote looks like

A complete quote does not need to be long. It needs to say whether the attic floor is included, what that covers, and who does it. If the answer is that it is not included, the quote should name the trade you need, and the cost should not be hidden inside the shingle total. A roofer who says the attic is outside their scope is not dodging the question. They are telling you the work sits outside their contract, and that is worth knowing before the price is compared with another bid.

Keys Roofing installs Atlas and Malarkey shingles, and the written scope Keys gives a homeowner sets out the roof work, the flashing, and the vent work in plain terms. If attic air sealing is something you want priced, ask for it as its own line so you can compare it fairly with any other bid. Call the office at (314) 220-2333 and ask the crew what they would need to see in the attic before tear-off day.

Questions to bring to the bid

1. Is attic air sealing in the scope, out of it, or listed as an allowance?
2. What count, length, or area is the price based on?
3. Which sealing material is named, and where will it go?
4. Who does the attic work, and does it happen before any new insulation?
5. Are the bath fans and the attic hatch in the same line or priced separately?
6. Does the insulation top-up stop at a stated depth, and is that depth in writing?

If the answers are short and specific, the bids are easier to compare. If they are vague, the attic is likely where the price will move after the shingles come off.