Flat roofs rarely fail all at once. They fail at a few details, one at a time, and most of those details are cheap to fix when they are caught early. A twice-a-year inspection is the cheapest roof maintenance there is. Here is what one should cover, whether the roof is over a row house or a 20,000-square-foot building.
When to inspect
- Spring: after the last hard freeze, to catch what freeze-thaw opened up over the winter.
- Fall: after the leaves drop, to clear drains and gutters and fix small problems before winter.
- After storms: high wind, heavy hail, or a tree limb on the roof.
- Before you buy or sell a house or building with a flat roof.
What you can check from inside and the ground
- Stains, peeling paint or soft spots on top-floor ceilings and along exterior walls.
- Water in the light fixtures or around skylights and roof hatches.
- Overflowing gutters or water pouring over the edge instead of out the downspout.
- Damp or cracked brick and mortar near the top of the walls and parapets.
- On commercial buildings, stained or sagging ceiling tiles.
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The on-roof checklist
Drainage
- Drains, strainers, scuppers and gutters clear and secure.
- Standing water or water stains showing where ponding happens. See ponding.
- Downspouts connected and discharging away from the building.
Field of the roof
- Seams tight, with no open laps, fishmouths or lifted edges.
- No punctures, splits, blisters or bare spots in granules or gravel.
- Membrane not shrinking or pulling at corners and edges.
- No soft or spongy areas underfoot, which point to wet insulation or decking.
Edges and walls
- Parapet and wall flashing tight to the wall, counter-flashing sealed.
- Coping stones or metal secure; mortar joints not open.
- Party-wall seams on row houses intact.
- Edge metal fastened and not lifting.
Penetrations and equipment
- Pipe boots, vents, exhaust fans and chimney flashing intact.
- Skylights and hatches sealed and not cracked.
- Rooftop unit curbs flashed, pitch pockets full and not cracked.
- No damage from service traffic around equipment.
Checking for wet insulation
On commercial roofs and any roof with insulation above the deck, the biggest unknown is what is under the membrane. Core cuts, infrared scans and moisture meters find wet insulation. That matters most before a coating or a recover, since neither should go over a wet roof. See repair or replace an old built-up roof.
What a good report includes
- Photos of the whole roof and of every issue found.
- Each issue ranked by urgency, and priced separately so you approve only what you want.
- An honest estimate of the roof's remaining life for budgeting.
- Notes for warranty records, if the roof is under a manufacturer warranty.
The bottom line
Inspect in spring and fall, keep the drainage clear, and fix small problems while they are small. See roof inspections.