A porch roof is a small roof with a big joint. It meets the house wall along a ledger board or a flashed line at the siding, and that line is where most porch leaks begin. If you see a stain on the porch ceiling near the wall, or water running down the brick or siding below the porch edge, the shingles over the porch may be fine. The problem is usually the seam where the porch roof stops and the house begins.
Leak and repair
Start by sorting out where the stain is. Water that enters at the wall often runs along the underside of the porch sheathing before it drops onto the ceiling, so the stain may show several feet from the actual entry point. Check the ceiling corner nearest the house first, then the ceiling line below the porch roof where it meets the siding.
On most St. Louis houses, a porch roof ties in with one of three methods. The first is a ledger board fastened to the wall with flashing above it. The second is step flashing run up the wall with the siding lapped over it. The third is counterflashing set into a reglet cut in brick or stone. Each one fails in a different way. A ledger nailed without flashing above it lets water run behind the wall. Step flashing installed without a kick-out at the lower end sends water into the wall cavity. Counterflashing set into a mortar joint can crack as brick expands and contracts through freeze-thaw cycles, which in this metro can happen dozens of times in a single winter.
Ask the crew to pull back the siding or trim at the joint, not just to look at the shingles. A shingle repair on the porch roof does not reach a flashing that sits behind the siding, and a caulk bead on the outside can make the joint look sealed when the flashing underneath was never lapped correctly.
What the damage usually looks like
- A dark stain on the porch ceiling along the wall line, often wider at the top than at the bottom.
- Soft or flaking paint on the trim board where the porch roof meets the house.
- White efflorescence on brick just below the porch edge, most visible after a wet week.
- Rot at the ends of rafter tails or in the fascia where gutter water runs back against the wall.
- A gap between the siding and the porch roof edge where caulk has split or pulled away.
None of these alone tells you the whole story. Caulk on the joint can hide a flashing that was never there. Efflorescence can appear after a dry month if the brick was soaked by a gutter overflow the spring before. Record what you see, with dates, before the crew opens anything.
Where the water actually gets in
The entry point is usually one of three places. The first is the top of the ledger, where the flashing was not lapped over the shingle course. The second is the step flashing at the wall, where the pieces were not woven with the shingle courses. The third is the corner where the porch roof meets the gutter return. Gutter water that overshoots the return dumps against the wall directly under the porch, and that water works into the joint slowly over years.
Ice damming at the eave can also push water up under shingles at the porch edge and carry it back toward the wall. In a St. Louis winter, a porch roof on the north side of a house can freeze and thaw repeatedly while the sun hits the house wall, which tests every seam where the porch meets the house. A leak that appears only after a hard freeze and a warm day is often pointing at this joint rather than at the middle of the porch shingles.
What it costs
A flashing repair at a porch wall is usually a smaller job than a full porch reroof, but most of the labor is access. The crew has to remove trim, lift or cut siding, and reset counterflashing, and each of those steps takes time. If the ledger has to come off to be replaced, the porch roof has to be opened to match, and the scope grows accordingly.
Ask for the repair to be priced as its own line with its own scope. The scope should state the linear feet of flashing being replaced, whether the siding is removed or only lifted, whether the trim is replaced or reused, and what the crew does with the gutter return at the corner. A line that says porch flashing as needed leaves you with a number you cannot check against the work.
If rot reaches the rafter tails or the sheathing under the porch, the repair gets larger. Rot is found only when the trim comes off, so the written scope should say what the crew does when they find it: stop and call you, or proceed within a stated limit. Keys Roofing documents any rot with photos and measurements before it is replaced, so the change is visible to you and not just to the crew.
What to ask
- Will you remove or lift the siding at the joint, and will you photograph the flashing before anything is covered?
- Is the ledger flashed above the shingle course, and will that detail appear in the written scope?
- Where does the gutter return discharge, and will the downspout at the porch corner be checked and corrected if it is short?
- What happens to rot found behind the trim, and who signs off before it is replaced?
- Will the photos and measurements be in my hands before the final payment is due?
If your porch leak is tied to an open insurance claim, Missouri law (RSMo 407.725) forbids a roofing contractor from representing or negotiating your claim, and from saying anything about paying, waiving or covering a deductible. 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. To have the porch joint looked at, call Roof Leak Repair St. Louis at (314) 220-2333.