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Advice for dormer window leak.

Discussion in 'Roofing and Guttering' started by Xenor, 6 Dec 2020.

  1. Xenor

    Xenor

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    I live in a townhouse with dormer windows on both sides, built in 2012 and I have a leak coming through to the box room directly below one of the dormer windows. I had a roofer out and he said there was mortar on the join from the dormer window to the tiles that was done wrong and blocking the channels that water is meant to run down and escape when rain hits the side of the dormer. I paid a decent amount of money for the roofer to go up and remove the mortar and he did so. However a month later it seems the leak is still there. It's only really noticeable after some persistent/heavy rain.

    I told the roofer about this and that the job did not fix the leak and I pointed out that the spot in my box room is directly below the dormer window. He came out to see what I meant and then had a look in my loft. He was saying the roof wasn't built properly as the felt has no counter battens and has a hole that was patched with gaffa tape. He said all the tiles on that side of the roof need to come off, felt redone and then the tiles put back and I'd be looking at £2-2.5k.

    He suggested I should contact NHBC and tell them my roof needs redoing. Seems odd as there are no signs of any water ingress in the loft, even where the hole in the felt was patched. It's a tight seal on the patch. NHBC won't help with the dormer, I already tried and they declined based on the fact they declined a claim from the previous owner 6 years earlier for the same thing (a claim the previous owner never declared when selling). I've not spoken with them about the counter battens yet, that sounds like a different issue. Are counter battens required? This is what my loft looks like:

    130166892_196493192018206_6356582586216504771_n.jpg 129702984_137849184529321_343194696072610435_n.jpg

    I should add that being a townhouse my loft is only half the roof space - the other half forms the sloping walls in the second floor bedroom so the loft space for that part of the roof is behind those walls.

    In the box room I had a hole in the ceiling that I made at the time I first noticed the leak so I could check the extent of the leak and today I've enlarged that hole so I could send a camera up there and access the hidden roof space. Turns out there is signs of water ingress on the beams right where I expected them to be - on the side of the dormer window. So removing the mortar has not fixed the leak. You can see this here:

    130237095_298960521441660_1214569084223882726_n.jpg

    I was originally worried he may have made the issue worse due to a hole I can see. This is how the side of my dormer looked before any work was carried out:

    122937352_354834859063725_1030128254656578790_n.jpg

    And here it is now:

    130190112_403833760664516_9011501775928771590_n.jpg 129658902_365760694725155_3436641352547495957_n.jpg

    You can see into the roof void if you look closely enough. Surely any driving rain heading in that direction would be able to get under there and bounce its way into that void. There should be felt under there but I don't know how it copes if it gets too wet.

    As I said I had a leak before the mortar was removed as well so the roofer may have been right about the mortar being done wrong and blocking the channel, but it looks like there was more to the problem than that.

    This is how the other side of this window looks:

    129726552_606012310153479_4957263458185896604_n.jpg

    Every house on my street with the same design as mine has mortar in these corners so it seems odd to just remove it - unless they were all done wrong.

    Do any experts here know what might be the cause of my leak and have any advice on how I should proceed?
     
    Last edited: 7 Dec 2020
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  3. datarebal

    datarebal

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    The roofer has tried to fix poor detailing.. doubt he made it worse.

    firstly i see a grp structure I have never seen one with properly thought out weathering design .

    The lead flashing in the picture has a back fall so rain will not run off well.

    Probably the water is backing up and running over the top or side edge

    the course of tiles below the flashing need their tops trimmed to allow the flashing to sit crrectly and to drain.

    the edges of the flashing need a more robust turn up.

    fwiw its nothing to do with no counter battens, they are not essential in this case.
     
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  4. catlad

    catlad

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    So they declined your leak because the previous occupant pointed it out 2 yrs after it was built and they couldn't be arsed correcting it then, so there not going to correct it now?
     
  5. Barthy

    Barthy

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    Data spot on
    Grp dormers often come with pre installed front aprons and site roofers tend to just cover the tile without regard for issues down the line.
    Obviously cutting X amount of tiles was too much hassle whilst on a tight price
    Gauge adjustment probably out of the question being close to eaves and size of tile
    These are hideous details and everyone knows it.
    The same can be said for grp chimneys.
    That said it shouldn't take a genius to rectify the problem and it doesn't require stripping the whole roof...without looking at any other pictures.
     
  6. Xenor

    Xenor

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    Thanks @datarebal and @Barthy. Some very good information there. I'm glad the removal of the mortar hasn't made the problem worse but it does seem odd that I can see into the roof void through there now.

    I think the lead flashing may be an issue as well looking at it as it is sloping back towards the roof due to the tiles not being cut. That is concerning though as no doubt it's an issue on both dormers, but no signs of leaks on the other one.

    My worry now is contacting another roofer and them doing work and still having a leak afterwards. I appreciate leaks are hard problems to solve but roofers aren't cheap. I might go back to the one I originally paid with these photos but surely he should have spotted these issues himself. Not sure if he'll sort it under the money I already paid, it's starting to feel like money wasted.

    @catlad The NHBC are as much good as a chocolate teapot to be honest. I don't know why they declined the claim back then, maybe it didn't meet their high minimum claim value. Annoying thing is the previous owner put on the PIF that they hadn't made a claim to NHBC, if I'd known I would have gotten the roof surveyed.
     
  7. regsmyth

    regsmyth

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    i could be wrong but doesn't photo 5 show the skirt having come unstuck from the fibreglass?
     
  8. Xenor

    Xenor

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    I'm a bit confused by what you mean by "skirt having come unstuck from the fibreglass"? Is the skirt the lead flashing? The fibreglass bit that sits on top of it isn't stuck. Not sure if it's supposed to be. It's the same on both dormer windows.

    I'm still lost as to where exactly the rain gets in. When it was raining yesterday I stuck an endoscope into the void in photo 6 and didn't see any signs of wetness. But rain was dripping into the room below. About one drip every 10 seconds so it's a very small leak.
     
  9. regsmyth

    regsmyth

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    This is the bit I thought looked "unstuck"...
    [​IMG]
     

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  11. Xenor

    Xenor

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    Yeah that is certainly not stuck down. I can get my finger under it in the middle without too much effort. Same on the other side of the house on the opposite dormer. I could imagine water getting under there but won't the lead flashing curve upwards and prevent it getting in there? I honestly don't know.
    I must add this photo isn't completely straight so the angles aren't as they seem, the roof slope is a bit steeper than it looks.

    To be honest I'm thinking about cutting into the wall in the second floor bedroom so I can access behind the dormer and have a better look. Then afterwards building a cupboard/storage space there. There is so much wasted space behind the walls. You can see what I mean in this photo:
    129361459_193680779069823_9169778531329285530_n.jpg
     
  12. datarebal

    datarebal

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    It does not need sticking down it needs correct fall to run off and plenty of head lap
     
  13. regsmyth

    regsmyth

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    Sorry I'm confused. Where do you see the leak in that last photo? Is your dormer the same as those in the background? Can you get a photo of the sides of the dormer where it meets the roof?
    In your first post you said the leak was directly below the dormer window, yet you also said you made a hole in the ceiling to see the damp timbers.
     
  14. Xenor

    Xenor

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    Apologies for confusing you. By directly below I meant the room underneath the dormer. The room you can see in my new photo is the upper bedroom. Look to the right side of the window, past the radiator - the wall comes inwards towards the room and then turns again towards that vacuum cleaner. Focus on the side wall that is coming inwards from the window. Behind that at the top is the dormer - where the angle is. Now imagine you went down there to the floor, and down below that floor. That is where the box room is, and the hole I made in its ceiling. That hole looks upwards into the void to the right side of the dormer. (or left if you're standing on the street). The location of the leak pretty much matches up to the side wall of the dormer.

    The dormer is identical to the ones on the houses in the background yeah, but the roof is made of a different tile - theirs are flatter. I can't get you a close up photo of the sides of the dormer where it meets the roof right now with it being dark, but I'll shove a camera on a stick out the window tomorrow and take one of each side. Here are a couple of photos I took from the street before my last attempt at a repair was done:

    dormer1.jpg dormer2.jpg
    You can see the top of the window in the bedroom for the box room I was talking about (bottom left) - the leak coming down into that room. So it's almost certainly somewhere along the left side of that dormer or bottom left corner. The roofer who came took the row of tiles off to the left of the dormer and took away the mortar that he said was blocking the drainage channels that sit under that row of tiles. But seems that was only part of the problem he solved. Although to be fair I've not noticed any difference in the leak at all since before/after that was done.
     
  15. regsmyth

    regsmyth

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    Ok understood thanks. Just me being a bit dense.
    As the others have said it shouldn't be too difficult to find out where the water is getting through once the tiles are lifted but your previous roofer should have sorted it out. The lack of mortar may well be an issue in heavy driving rain and reinstating it will help stop debris getting trapped under there. Buy a ladder and do it yourself?
     
  16. Xenor

    Xenor

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    Yeah I don't understand why the previous roofer couldn't find anything else wrong with it. Then again I'm not sure he checked. He just came, said it was the mortar and that these dormers shouldn't have been installed with mortar there, then came back the next day to do the job. The lack of mortar does concern me as I saw a leaf in there the other day when I put a camera inside. The leaf looked like it was fresh from this Autumn and had gotten all the way into the void of the roof, so if a leaf can get there debris could block those drainage channels. Worried about snow sitting next to the window and blowing in then melting too. I think mortar should be there but done properly. I could probably lean over and put mortar back from the window but I'd be worried about blocking the channels by applying too much mortar.

    As for removing the tiles and investigating the actual leak, I definitely wouldn't trust myself to go up there on a ladder. I could hire a scaffold and investigate but even then I won't know if the repair is within my capabilities until I know what needs doing. Might be hard to see where water is getting in as well with it being small amounts of it. It must be seeping down a gap very slowly somewhere. So I was thinking about making a hole in the wall near the dormer to have a closer look from the inside before I do anything else. It's hard to see properly from the hole in the ceiling in the room below.
     
  17. regsmyth

    regsmyth

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    I wonder if there's a possibility water's getting in at the top of the dormer , and running down the felt under the tiles till near the bottom of the dormer side where there could be cuts/overlaps for it to seep through.
     
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