Roof repair in Washington, DC

Most of the city sits under three kinds of roof. Rowhouses from Shaw to Trinidad have low-slope roofs hidden behind a front parapet, usually covered in modified bitumen, EPDM, aging coated roll roofing or a newer white TPO sheet. Victorian blocks carry steep slate mansards on the street face. Upper Northwest and the inner suburbs add detached colonials and bungalows with asphalt shingles, cedar or slate on pitched roofs.

Each one fails differently, so we arrive with materials for the roof we are walking onto rather than a generic patch kit. On a low-slope rowhouse that means membrane, primer, a torch or heat welder and termination bar. On a mansard it means slate of the right size and thickness, copper nails and slate hooks. On a colonial it means shingles in the closest available color, ice and water underlayment and new pipe boots.

Porch roofs and rear bay roofs deserve their own mention. They are shallow, often tied into a brick wall with tired flashing, and they collect leaves from street trees. A large share of the calls we get from Petworth porch-front homes trace back to that wall joint rather than the main roof.

We repair when the damage is local and the rest of the roof still has life. A membrane that is pliable, well adhered and without widespread blisters can take a patch that lasts as long as the field around it. Shingles that still hold their granules and lie flat can take a few replacements and a new boot without trouble.

We start talking about full replacement when the problems are everywhere at once: alligatored coating over brittle felt, seams opening in several places, soft decking under foot, or shingles that have lost most of their granules. Patching a roof in that state buys a season at most, and you pay for another trip up the ladder the next time it rains hard.

Slate is the exception that surprises people. A slate roof with broken pieces and rusted nails is usually still a repair job, because good Pennsylvania or Vermont slate outlasts the nails holding it. Our page on repairing a slate roof explains how we replace individual pieces without disturbing the course above.

Rowhouse roofs are reached through an interior hatch, from a neighbor's roof with permission, or by ladder from the alley. We ask about access when you call so the right ladder and fall protection come on the first trip. Street parking near Logan Circle or Capitol Hill can be tight, so we often stage from the alley and carry materials up by hand.

On the roof, we look past the obvious spot. Water on a ceiling under the middle of the house can start at a parapet cap, a vent stack or the gutter at the rear wall. We probe seams, check the flashing where the roof turns up the party wall, look at the scupper and downspout, and photograph everything before we cut anything.

Then we fix the cause with materials that bond to what is already there. Mod bit gets torched mod bit, EPDM gets EPDM with the correct primer and seam tape, and TPO gets hot air welded TPO. Mixing incompatible products is one of the most common reasons a patch from another crew lets go after one summer.

Summer in DC brings afternoon thunderstorms that can dump an inch of rain in an hour, and that is when weak seams show themselves. Heat also helps us: membranes weld and adhere best on warm, dry days, so June through September is good repair season for low-slope roofs.

Winter work is possible but has limits. Adhesives and sealants have minimum temperatures, and slate becomes brittle when it is cold. On a 30-degree morning we can still replace shingles, reset flashing and make a sound temporary repair, then come back for permanent membrane work when the forecast warms.

Fall is the season we push for small repairs before they grow. Leaves from oaks and tulip poplars pile up in gutters and scuppers, and a clogged outlet on a flat roof turns a minor seam problem into standing water against the parapet. Clearing and repairing in October heads off the January leak.

You get photos of the damage, the repair in progress and the finished work, plus a short note on what else we saw. If another part of the roof is close to failing, we tell you plainly and give you a rough idea of what it would cost, so you can plan instead of reacting.

Keep an eye on the ceiling below the repair after the next two or three heavy rains. A dry ceiling means the cause was found. A stain that grows tells us water is entering somewhere else, and we come back to trace it rather than adding sealant over a guess.