How to test for dormer roof leak.

on 14/08/2014, AnthonyL supposed :

I would suspect, that the water around the window, is tracking over the top of that exposed lintel. You could confirm that theory by spraying the lintel with a hose. Your water damaged wallpaper further into the room, is likely due to wind blown rain getting under the tiles.

You could test the theory further, by sticking a temporary strip of that sticky backed plastic lead flashing to the wall face, so it over hung the lintel forming a 'drip strip', hanging loose a little way below the lintle.

Absolutely not an expert, but that is the way I would play it.

or under the lintel, and there's no seal between the lintel and the window (expanding foam isn't a water seal).

However, there's a valley gutter just above both leaks, and these can leak if the lead lining cracks or there's some other fault with them. Can't see in the picture.

The right-hand end bricks don't look like they're bedded onto the lintel at all - just sitting directly on it.

The most obvious design fault is that there is no overhang of the roof. ie It should project beyond the brickwork (over the window) so that water that drips from it falls clear of the wall. It appears to be virtually flush which may well let water in. The roof structure should project at least 100mm beyond the brickwork and should be arranged so that wter drips off the edge and does not run back towards the wall.

You could confirm this by putting a silicon bead along the juctions whch would fix it. But this would only be a temporary fix.

You might be able to put some lead on it but it would look pretty s**te. I would be hard/expensive to fix properly, the roof over the dormer would have to be removed and new longer battens fitted with tiling to suit.

harryagain pretended :

You can now get a 90 deg tile, which overlap down the wall, but how that would work matching into old tiles I don't know. Our tiles only overlap by about 25mm, with the edges f launched with cement to the wall. We have never suffered any leaks.

The entry point is a couple of courses above the lintel. I'll still spray to make sure.

Well I can spray from different angles. The roof is about 45deg so not sure why water/damp should get under. I can't see anything from the loft.

At this stage I want to make it happen not stop it from happening. Very hard to prove a negative.

Finding an expert seems very elusive. This is a DIY that I am doing very reluctantly.

How should it have been sealed?

I think I've only got one leak - the web page shows problems that existed before and those that still exist. Where are you reading two leaks?

I'll try soaking the valleys. They may date back to the 1860's so there may be some porosity. My main worry is that we've had the odd thunderstorm and the water hasn't come in - maybe it's got an internal reservoir and the water is being held until it reaches a certain level?

I'll look at this more closely. I think the lintel was supposed to have been 6" into the brickwork at the sides. However I'm not having a problem on that side (yet).

It's worse than that, it actually projects out. The original (1860's) design did half the window half a course inset as the early pictures show.

At this stage I'm more interested in proving where the problem is than solving it. This is so once I instruct someone to fix it I can test that it is really fixed.

It may be that the whole of the brickwork will need to be taken out, and re-done properly instead of in its current "wibbly wobbly" condition. At the same time a treated lintel can be installed instead of the bare metal one this 'builder' used.

Up to 1/4" wide, silicone sealant is usually used. If it's wider that that, it should have had a piece of facing PVC added, and silicone sealed around the edge of that. There shouldn't be expanded foam showing - it's not weatherproof (frost and UV will do for it).

If the lead was well done, it should last about 70 years. Eventually, heat cycling in the sun causes it to crack across. Longer pieces tend to have shorter lives (due to more expansion).

It may be directional, and thus depend on the direction and magnitude of the rain.

Is the lintel new(ish)?

I hope so. I was surprised to see that, to put it mildly. IME and especially down here where we get a lot of salt gales, untreated steel will quickly bleed rust through any coating you apply and it will always look horrible.

Sometimes the *experts* have blinkers, the opinions on here while often contrary to one another, sometimes get the correct answer from experience and also from lateral thinking (there are also some good experts here as well)

JTM