Home & Garden7 mins ago
Flat Roof Problems
14 Answers
I have an old Victorian house which has a single storey extension to the side, with a flat roof. Last winter (which was very wet) there was a leak in the kitchen adjoining it, and problems with damp getting into the wall and electric sockets. I had the flat roof painted with waterproofing material twice, but apparently (I don't live there) the kitchen wall is still damp and peeling. I spend loads of money trying to get this fixed last year and it really needs sorting once and for all. What can I try? I could get the whole roof re-done, but what if the problem is higher up, maybe the flat above has a roof tile which is letting water into the building and water is running down the inside wall? I've had several contractors look at this now and I really need it fixing. Any advice gratefully received!
Answers
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Ah....... 9:35pm ....... er ........ I was in the pub :o)
One of the most common problems with this sort of arrangement, is where the flat roof joins the building. Often, people spend a lot of time on the flat bit, but forget that the "abutment" is the most vulnerable area.
Let's assume that the flat bit is now watertight. If not, you would see staining and leaks towards the middle of the ceiling. Your problem is water running down the wall.
Am I right, that this wall is the one between the house and the extension?
Is there a lead flashing? It should be let into the wall above the flat roof. It should then drop down just a few inches to cover the edge of the flat roof where it abuts the house.
Is this exterior wall rendered, or exposed facebrick?
One of the most common problems with this sort of arrangement, is where the flat roof joins the building. Often, people spend a lot of time on the flat bit, but forget that the "abutment" is the most vulnerable area.
Let's assume that the flat bit is now watertight. If not, you would see staining and leaks towards the middle of the ceiling. Your problem is water running down the wall.
Am I right, that this wall is the one between the house and the extension?
Is there a lead flashing? It should be let into the wall above the flat roof. It should then drop down just a few inches to cover the edge of the flat roof where it abuts the house.
Is this exterior wall rendered, or exposed facebrick?
Yes, you're right. The flashing I think is intact or they would have replaced it when I asked them to sort it out. The exterior wall is rendered brick. Above it is another storey with a flat roof, ie- extension. So, my flat roof is a jutting out bit, and adjoins to the main extension, which also has a flat roof. I can send a photo!
Victorian solid wall construction - probably 9" brickwork. It does rather sound like rainwater penetration, horizontally through the wall. 9" of masonry, even if it's rendered, can become completely waterlogged........... especially if facing south-west.
I'm assuming that rainwater soaks the brickwork, then shows up in the room below.
The big problem here, is coming up with theories, making expensive alterations/improvements, then finding it was something else entirely.
I think I would try a little cheap experiment. Give the wall above the flat roof a couple of coats of water repellent............
Amazon.co.uk User Recommendation
It's formulated to soak into the masonry, and does work extremely well. It's not a final solution, but remains effective for a few years at least. It's clear, and easy to apply.
Two or three cans of that isn't going to break the bank, and it may well tell us what we need to know.
I'm assuming that rainwater soaks the brickwork, then shows up in the room below.
The big problem here, is coming up with theories, making expensive alterations/improvements, then finding it was something else entirely.
I think I would try a little cheap experiment. Give the wall above the flat roof a couple of coats of water repellent............
Amazon.co.uk User Recommendation
It's formulated to soak into the masonry, and does work extremely well. It's not a final solution, but remains effective for a few years at least. It's clear, and easy to apply.
Two or three cans of that isn't going to break the bank, and it may well tell us what we need to know.
Hi Scarlett. As a builder, there are a couple of things I'd be looking at. I'd like to see if there's any penetrating damp showing up in the room right above your kitchen.
Also, there's a lot of exterior plumbing on that wall.
Upstairs' gutter downpipe runs the whole height of the wall, and looks as though it discharges via an extended piece that lands in your lower (kitchen gutter). That's messy, and a potential problem. It may be becoming overloaded in heavy rainfall. I think I would re-arrange that, even if it's not the cause of the present problem.
I would check that whole downpipe for cracks and leaks.
Also, there's a soil pipe arrangement (black). I can't see it properly in the picture, but it seems oddly placed. Perhaps there's a WC in the room above the kitchen. I'd be interested to know why it comes out the side onto your flat roof, but then turns to discharge around the front. Soil pipes through walls and flat roofs are a common source of leaks.
Back to the lead flashing where the wall meets your flat roof ........... The render looks like it ends with a "bellcast" (swept out a little at the bottom). I'd be inclined to break into just a little piece of that to confirm that a good lead flashing is in place.
The upper part of the wall is well exposed. Not only does it get wet, but it also can dry (evaporate) quickly. The lower part is quite different. Your flat roof is in an enclosed area of mostly stagnant air. Air circulation will be poor. I still think there's a possibility that the wall gets overloaded when wet. It's a very poor design to create such dank areas, but quite common.
To rule out (or even in) the rain penetration thing, I would go with the water repellent. That render is a doddle to do. It'll take no time at at.
As for the flashing and the plumbing, a simple visual inspection can show very little. I'd want to get in there and poke about......... looking for trouble. Even if things have to be dismantled, they can soon be re-assembled, and damage repaired.
Builders called out to look, are naturally loathe to disturb anything, but, in this case, I think we have to be a little proactive, as they say.
Also, there's a lot of exterior plumbing on that wall.
Upstairs' gutter downpipe runs the whole height of the wall, and looks as though it discharges via an extended piece that lands in your lower (kitchen gutter). That's messy, and a potential problem. It may be becoming overloaded in heavy rainfall. I think I would re-arrange that, even if it's not the cause of the present problem.
I would check that whole downpipe for cracks and leaks.
Also, there's a soil pipe arrangement (black). I can't see it properly in the picture, but it seems oddly placed. Perhaps there's a WC in the room above the kitchen. I'd be interested to know why it comes out the side onto your flat roof, but then turns to discharge around the front. Soil pipes through walls and flat roofs are a common source of leaks.
Back to the lead flashing where the wall meets your flat roof ........... The render looks like it ends with a "bellcast" (swept out a little at the bottom). I'd be inclined to break into just a little piece of that to confirm that a good lead flashing is in place.
The upper part of the wall is well exposed. Not only does it get wet, but it also can dry (evaporate) quickly. The lower part is quite different. Your flat roof is in an enclosed area of mostly stagnant air. Air circulation will be poor. I still think there's a possibility that the wall gets overloaded when wet. It's a very poor design to create such dank areas, but quite common.
To rule out (or even in) the rain penetration thing, I would go with the water repellent. That render is a doddle to do. It'll take no time at at.
As for the flashing and the plumbing, a simple visual inspection can show very little. I'd want to get in there and poke about......... looking for trouble. Even if things have to be dismantled, they can soon be re-assembled, and damage repaired.
Builders called out to look, are naturally loathe to disturb anything, but, in this case, I think we have to be a little proactive, as they say.
Hi Scarlett, You sound like you have a similar problem to me. We live in a victorian house split into 4 flat, 2 above but we have the flat roof, every year we get a leak in 3 different places until finally in January we had an entirely new roof. Imagine our dismay when this weekend we found the leaks again. Have you managed to fix yours at all? We are now at a loss as to what to do?
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