extension roof no room under window for flashing

20 Feb 2015
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United Kingdom
Hi looking for advise on where to go with this. Not happy with the roof finish on our extension, damp on the now internal house wall has blistered paint, when it was really stormy it was like a water fall inside the house, the builders came out quick but just applied lots of silicone everywhere and it did seem to stop the water fall, but only over time will we know if there’s still moisture getting in causing damp

Long story below, but question in short (er):
The 15deg roof came hard up to the window concrete cill so the flashing was tucked under the Upvc window (with Upvc cill), and over the top of the concrete one. The flashing at the window sides it was not raggled into the render but just silicone to it. Should the concrete cill have been removed and flashing put under it, or is what has been done acceptable just not to a good finish? I’d like to know how I approach the builders who say its fine,although still chasing the architect for comment but the original design was to flatten the roof at window so flashing would fit under, this wasn’t possible.

Long detail…

3.5 by 5m lean to ext on 1950’s house, 15deg tiled roof, vaulted ceiling with cold space, rigid insulation between & under joists. Finished Jul-14
South facing in a level 4 environment??? (there’s a windfarm directly opposite so we get hit with everything.)

-Roof boarding & tiles stop about 25mm short of main house, gap covered with flashing – lift the flashing stick your hand down easily..
-Gap also on internal side as insulation stopped short, tapped and filled with plaster (now brown stained from damp).
-I assume there’s a Timber beam across length of wall held in with long bolts up there.

Roof comes under bedroom window. Original drawing showed the flashing running along then having to dip down under window and back up again to get the 150mm vertical. No detail how to ‘flatten roof to allow space to do this.
When built the tiles stopped 10mm under the concrete windowsill (even less space, and no flatted part made to bring the roof in lower down), reason was a lintel was missed off height calcs for back door.

Between the builder, designer & agree by BC (they never even wanted to look at it when inspecting) it was agreed to remove the window and tuck the flashing under the window cill then replace window.
We agreed to buy a better window for security purposes.
The flashing was tucked under the uPvc cill that came with the window. when it came to the sides it was cut and shaped and sealed on top of the roughcast. I doubt the underside of the cill was mastic’ed to the flashing.
The window was moving (2m wide) so they stuck screw through the frame and down through the flashing underneath.
Flashing over concrete cill only has 50mm lying on tiles so a 2nd row of lead was laid underneath flat against the tiles ie not turned up at all, to extend it.

Other points
-flashing was not raggled 25 mm into wall (as per Drg) but as we got the house re-roughcast, they put a metal bead along and tucked in under this.
-The ingels round the window were rendered after window install and not all way down to the concrete cill as the flashing & plastic cill blocked it, the gap wasn’t sealed, It then cracked badly, being pulled off by the sealant round the window (this is the sole cause of the ‘waterfall’ we experienced during the stormy weather but I can’t belive only a few mm of concrete is all that stops that amount of water coming in)
-The sealant inside the window has all split twice through movment and we can feel draughts around it. They do not use expanding foam anywhere, but are fans of stuffing holes full of glass wool (£3 a roll?..)

Again any advice you can offer, or where I can get formal advice to contest the work (feel there's things that both architect and builder is at fault). I have no faith in the BC sadly as they weren’t interested at the time.
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A 15 degree pitch roof in high risk (windy) area? :eek:

The least that should have happened is that the builders and architect should have come up with an uber-robust felting/membrane sarking detail that should keep out the rain irrespective of roof tiles and flashing.

Someone should have stood over the guy doing the lead flashing so that this was done with great care with special attention paid to masonry chases, laps, and head cover.

Can you post a photo of the roof?

I have no faith in the BC sadly as they weren’t interested at the time.
BC have no remit on work quality so don't expect them to babysit builders.
As above, really.

The 'designer' should have come up with a detail to drop the roof slightly below the cill to get the flashing in - not difficult to design or build, though the leadwork should have been done by a plumber rather than 'builders'.

Was a cavity tray fitted, or have I missed that?

Who got the lintel detail wrong, builder or designer?

And no, building control are only concerned about health and safety, not workmanship - it's a common misconception.
HI thanks for the responses, now that it's better weather I've managed to take some pictures. As you can see the flashing under the window is just siliconed at the sides. The thing you can see under the Upvc cill is some material the builders stuffed in there after calling them out to do something about the water pouring in. The inside picture to show the water damage with paint peeling over a metre down from the roof line.

Cavity trays weren't in the drawings.
Definitely wasn't the plumber, he was sub contract and only did the water & central heating work. If you could elaborate on your comments about "special attention paid to masonry chases, laps, and head cover." that would be great or if there's pictures, even better.

Hopefully this will help you understand the arrangement. As mentioned previously the only fixing holding the window at the bottom is a single 4 inch screw that goes through the frame, then into the flashing, they only added this after I commented on it moving. And the lower layer of lead just lies flat on the tiles, no turning up under the upper layer.

Again thanks for any advice you can offer.

PS you also see the lots of sealant slopped round the soil pipe,

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Amateurish at best.

We would have renewed that section of SVP in plastic as well, prior to building the roof. We would have then slid a pitched multi-slate over the SVP and done it properly.

Seeing as you are in a high risk wind area, that flashing abutment is pants. We would have considered a less deep window or a recessed box flattie so that the area under the sill could have been done properly.

Overall, in a location that commanded a lot of attention to detail, you have ended up with a flashing abutment that has been afforded very little.
How long as this been built and how much has it cost.
They started a year ago on an estimated 12 week (max, on signed contract) build and finished 23 weeks later, with us canceling some work separate to the extension and setting an ultimatum. We needed them away as we were dealing with illness within the family at that time. Cost upper £30k's (including removing an old small extension)

Thanks Noseall. We were probably pig headed about the soil pipe, the architect said same as you that it'll probably be replaced with a plastic one, he didn't even show it on the drawing, I drew it on before supplying a copy to the builders but as nothing stated to replace it, they fished for more money to do it and do regret that one. Overall I agree it doesn't look professional at all. Our thoughts are to get a quote from some professional roofers and get them to fix it then see what can we do about compensation (unlikely I'm sure).

The roof has been my main concern, but not the only one as the extension is freezing due loads of draughty leaks, including air blowing through plug sockets?? and underfloor insulation dropped due to poor fit and support, grrrr. Anyway thanks for your thoughts, I'll not go off on a rant.

Oh and to answer the other post question. The builder claimed the architect messed up with the lintel and caused the roof to be so close to the concrete cill but if this was the case I'd have thought the internal ceiling height would have been higher than the size on the drawing.

The reason I was asking how much it cost was if you paid £15k for a £20k extension then that what you can end up with, but if you are telling me you paid £30K and they did not even sort out the drainage and left the roof like that then they are taking the ****.
The reason I was asking how much it cost was if you paid £15k for a £20k extension then that what you can end up with, but if you are telling me you paid £30K and they did not even sort out the drainage and left the roof like that then they are taking the p**s.
Yeah, well that's how we feel but it's getting someone reputable who can support us in getting it put right and not a five quid job that'll leak next year.

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