Your Flat Roof Is Leaking: What to Do in the Next Hour

The short answer: deal with the inside first. Catch the water, move whatever it can ruin, kill the power to that room if anything electrical is near it, and photograph the ceiling now rather than later. Stay off a wet flat roof, and seal nothing until somebody knows where the water is getting in.

What comes first, inside?

Containment, then everything that cannot be replaced. A bucket under the drip and a towel round its base stops the second problem, which is the floor, and a bin bag over furniture buys you time to move it properly. Water finds electrics before it finds anything else worth worrying about, so if a fitting, a socket or a loft hatch is anywhere near the wet area, switch that circuit off.

Then open a window in the room if the weather allows. A room that is taking water in is also gaining humidity, and the damage that follows a leak indoors is often as much about what the air does over the following fortnight as about the water itself.

What should you photograph, and why now?

The ceiling, the wall below it and the wider room, with your phone showing the date. Photographs taken while it is happening are worth more than any description afterwards, and the one thing nobody can reconstruct later is how fast a stain grew.

Take the same shot each time it changes rather than one dramatic picture at the end. Two images a week apart, from the same spot, settle arguments about whether a problem is spreading that a hundred words cannot. Where the damage came from a storm rather than from age, what an insurer expects to see is a different and more demanding list, set out on storm damage repairs.

What should you not do?

Three things, in order of how badly they go wrong. Each is common, and each costs more than the leak did.

• Do not go up on a wet flat roof. A mineral surface that is fine dry is treacherous wet, edges are rarely protected on a domestic roof, and a covering already failing may not hold your weight over a soft patch. Nothing you can see from up there is worth the fall.
• Do not seal over a wet build-up. Sealing a roof that has water inside it traps the water against the deck, which turns a covering problem into a structural one. It also hides the evidence of where the water was getting in, so the next person to look is starting from scratch.
• Do not chase the stain. Water enters at one point and travels along whatever is under the covering before it drops, so the mark on the ceiling is simply the lowest point it reached, not the place it got in. Repairs aimed at the stain are the single commonest way to pay twice and still be wet.

What is worth writing down before you call anyone?

Four things, and they take two minutes. Anybody competent will ask for them, and having them ready turns a guessing game into a useful first conversation.

• Where it shows. Which room, which part of the ceiling, and whether it is one point or several.
• When it started, and when it worsens. First noticed, and whether it is arriving now or has been coming and going for months.
• What the weather was doing. Whether it follows rain at all is the single most useful fact you can offer, because water that ignores the forecast may not be a leak. That is the point of the condensation test, and it is worth running before anyone is called out to a roof that turns out to be sound.
• How the roof is reached. Through a window, from a flat below, from a garden, or not at all without equipment. It changes what any visit involves before it changes anything else.

Send those with a photograph and the reply can be about your roof rather than roofs in general. What happens next, including how the source is traced, is set out on flat roof and leak repairs.

What does a temporary measure actually achieve?

It keeps the inside dry while a proper repair is arranged, and that is all it does. A sheet dressed over a failed area, an outlet cleared, a split closed against the next front: useful, honest, and not a repair. Anyone describing that work as a fix is either confused or hoping you are.

The reason to be clear about it is that holding measures have a habit of becoming permanent. A leak that stopped is a leak that stops being urgent, and the covering underneath carries on failing quietly until the following winter finds a new way through. If somebody buys you time, use the time.