Most porch roof leaks start at the joint with the house wall, where the flashing has failed or was caulked on top of the siding. Shingles on a slope too flat for them, ice at the porch eave and a backed-up gutter are the other common causes.
Get My Free Estimate →Most porch roof leaks start where the porch roof meets the wall of the house. The flashing there has to tuck behind the siding, and when it was nailed on top and caulked instead, water gets behind it within a few winters.
The other common cause is a porch roof too flat for shingles. Buckshot repairs porch roofs across Madison from our office on North Sherman Avenue, and this guide shows how to tell which problem you have.
Where porch roofs leak
Where the water shows up points to where it gets in.
| What you see | Likely cause | What it takes |
|---|---|---|
| Stain or drip where the porch ceiling meets the house | Failed flashing at the house wall | Re-flashing behind the siding |
| Stain inside the house on the wall next to the porch | Water running behind the siding above the porch roof | Wall flashing and siding repair |
| Rot or stains at the lower corner where the porch roof ends at a wall | Missing kickout flashing | A kickout flashing |
| Stain in the middle of the porch ceiling after long rains | Shingles on a slope too flat for them, or a worn membrane | A membrane roof |
| Drips at the outer edge or beam during a thaw | Ice at the porch eave or a backed-up gutter | Ice dam work, drip edge and gutter repair |
Where the porch roof meets the house
Most porch roofs end against the house wall, and that joint depends entirely on flashing. Along the top, an L-shaped headwall flashing runs up the wall behind the house wrap and siding, so water running down the wall lands on the roof instead of behind it.
Where the porch roof slopes along a wall, step flashing goes in with each course of shingles. At the bottom of that run, a kickout flashing turns the water away from the wall and into the gutter.
The common failure is flashing nailed on top of the siding and sealed with caulk. Caulk cracks after a few freeze and thaw cycles, and then water running down the wall goes straight behind the flashing.
On a brick wall, the roof flashing should be covered by counterflashing set into a mortar joint. Our guide to flashing repair covers how failed flashing is traced, and our chimney and flashing repair crews rebuild these joints.
Porch roofs too flat for shingles
On many older Madison homes, including bungalows, the porch roof is close to flat. Asphalt shingles need a slope of at least 2 in 12 under the building code and shingle makers' instructions, with an extra layer of underlayment up to 4 in 12.
Shingles on a flatter roof than they are made for hold water in the laps, and wind-driven rain and snowmelt back up under them. These leaks often show in the middle of the porch ceiling and get worse after long rains.
Below roughly 3 in 12, a sealed membrane is the better roof. Our flat and low-slope roofing crews install modified bitumen, EPDM and TPO on porches and additions, and our guide to roof pitch explains how slope decides the material.
Our guide to flat roofing in Madison compares those membranes and covers converting a flat porch roof to a pitched one.
Ice dams and snow on porch roofs
A porch roof sits below the main roof and over unheated space, so it collects what the main roof sheds. Snow slides down onto it, and meltwater from the warmer roof above runs down and freezes at the cold porch eave.
Snow also piles against the house wall where the porch roof meets it. As that snow melts, water sits right on the wall flashing, which is why some porch leaks only show up during a thaw.
Our guides to roof leaks when snow melts and ice dams in Wisconsin explain both patterns. For ice already backing water in, our ice dam removal crews respond within 2 hours and use low-pressure steam that protects the roofing.
Why the leak shows up somewhere else
Water that gets behind the wall flashing runs down the sheathing before it shows. The stain can appear on the porch ceiling away from the wall or inside the house on the shared wall, and our guide to water stains on the ceiling explains how leaks travel.
The board most at risk is the ledger, the framing board fastened to the house that carries the house side of the porch roof. Soft wood, a porch ceiling sagging near the wall or peeling paint on the porch beam mean water has been getting in for a while.
Porch ceiling stained or dripping? Our roof leak inspection is free, and we find where the water enters before quoting any repair. Call (608) 909-9109 to schedule it.
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How a porch roof leak is repaired
- Find the entry point. The wall joint, the roofing, the edge and the gutter are checked together, and a course of siding comes off at the wall if the flashing is suspect.
- Re-flash the wall. Headwall and step flashing go in behind the house wrap and siding, a kickout goes in at the bottom corner, and the siding goes back over the flashing. On brick, counterflashing is set into a mortar joint.
- Replace rotted wood. Wet decking, the ledger and rafter ends are cut out and replaced before any new roofing goes on.
- Match the roof to the slope. A porch roof too flat for shingles gets a sealed membrane, and a steeper one gets new shingles with ice and water barrier at the eave and along the wall.
- Fix the edge. A drip edge goes on, and the porch gutter is re-hung and pitched as part of gutter repair so water leaves the roof instead of backing up.
Our Madison roof repair crews handle the flashing, roofing and wood together, and our siding repair crews put the siding back over the new flashing. If the main roof is due too, our residential roofing crews can do the porch and the main roof as one job.
Porch roofs in Madison historic districts
If your home is a Madison landmark or sits in one of the city's five local historic districts, exterior changes need approval first. Those districts are First Settlement, Mansion Hill, Marquette Bungalows, Third Lake Ridge and University Heights.
The city's Landmarks Commission must approve exterior alterations to these properties with a Certificate of Approval, applied for before the building permit. Raise a change to a porch roof's material or shape with the city's preservation planner before the work is scheduled.
A porch reroof also needs a Madison building permit like any roof replacement, and our guide to roof permits in Madison covers that side.
Get your porch roof checked
Buckshot Exteriors is family-owned, has served homeowners since 1979, and is headquartered on North Sherman Avenue in Madison. Our own crews repair flashing, roofing and siding together, and our Madison roofing page covers the rest of our work in the city.
Call (608) 909-9109 to schedule a free roof leak inspection, or send us a message and we will set a time. If water is coming in now, the same number is answered 24/7.
Get a straight answer on your Madison roof
Wisconsin storm season and insurance non-renewal letters do not wait. Get a free, no-obligation inspection and an honest assessment of exactly what your roof needs, even if the answer is to wait.