Why the fall check matters on a rowhome roof
The City's Philadelphia Rowhouse Manual points out that most rowhouse roofs look flat but are built to slope toward a drain, and recommends at least 1/4 inch of fall per 12 inches. Water leaves through a roof drain or a scupper (an opening in the parapet or cornice) at the front, or a gutter at the rear, then runs down the downspout. The Department of Energy's Building America flashing guide agrees that a "flat" roof should never be truly flat. If leaves or a clogged downspout block that path, water sits on the roof, and the seams and flashing are where it finds its way in. Our guide to flat-roof drainage on Philadelphia rowhomes covers how the drainage path works in more detail.
What to check, from the roof hatch or a safe ladder
Only go up if you have safe access and the roof is dry, and stay well back from the edge. Look for:
- Leaves, grit and debris in the roof drain, scupper and rear gutter. The Rowhouse Manual lists cleaning gutters as routine maintenance.
- Puddles a day or more after rain. The National Park Service's Preservation Brief 47 lists bubbled surfaces and moisture ponding on flat or low-sloped roofs as warning signs.
- Blisters, splits, or open seams in the roofing, especially where the roof meets the parapet wall.
- Cracked or lifted flashing at the chimney, vent pipes, skylights, hatch and any rooftop equipment. Brief 47 also flags deteriorated flashing where roof areas meet each other or a wall, and cracked masonry or dislodged chimney caps.
- Leaves and debris trapped around the base of a rooftop air-conditioning unit, which Brief 47 says to clear out.
- A worn or missing silver or white coating. The Rowhouse Manual calls sunlight the roof's worst enemy and says a reflective coating protects the roofing and cuts heat on the top floor.
Then go back down and watch the downspout during the next heavy rain. If little water comes out while the roof is wet, the drain or pipe is likely blocked.
What kind of roof you have changes the repair
The Rowhouse Manual describes two common rowhouse roofs. Modified bitumen comes in rolls with a granular or coated surface, and a roofer can usually find its leaks fairly easily. EPDM is a black rubber sheet, and leaks in it are harder to trace. Flashing is the most common place for both to fail; see our guide to why so many roof leaks start at the flashing.
If you have a roof deck, the Manual says the walking surface should be removable so the drain and roofing under it can be checked and cleared.
Where the water goes matters too
The Rowhouse Manual says roof water must end up in the sewer system, and that it's illegal to send it onto sidewalks, streets or a neighbor's property, where it can freeze into ice. L&I's roofs and drainage violation guidance says roof drains, gutters and downspouts must be kept in good repair and free from obstruction, and that a missing, leaking or damaged downspout is a violation. If a downspout empties onto the pavement or into the house next door, get it fixed before the first freeze. If you've already received a notice, our guide to handling an L&I code violation notice explains the next steps.
During winter
After a big snow, the Building America guide to managing snow loads lists warning signs of too much weight: sagging or bowing in the structure, doors that suddenly stick, and creaking or cracking sounds. If you notice them, don't climb onto a snow-covered flat roof yourself; that guide recommends hiring a snow removal contractor.
When to call a roofer, and what to ask
Call a roofer for any active leak, ceiling stain, soft spot, wide blistering, or flashing that has pulled away. L&I's guidance is to hire a licensed contractor to evaluate a leaking roof, and warns that ignored leaks can lead to ceiling collapse and serious structural damage. Ask:
- Is the roof modified bitumen or EPDM, and how many layers are on it now?
- Where exactly is water getting in, and is the repair a patch, a recoat, or a replacement?
- Will you clear the drain and test the downspout as part of the job?
- If you replace the roof covering, will you pull the permit?
On that last question, the City's EZ permit page lists roof covering replacement as work that can use a permit without plans; most are processed in about five business days, and some are issued immediately when a licensed contractor applies. Our guide to when a rowhome roof replacement needs a permit has the details. These are City of Philadelphia rules; Bucks and Montgomery County townships set their own permit rules for roofing.