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Water pooling in pitched roof felt underlay

Discussion in 'Roofing and Guttering' started by TobyLeRone, 14 Jan 2021.

  1. TobyLeRone

    TobyLeRone

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    Hi everyone, just looking for a bit of independent advice until I get a professional in to take a look. We moved into a 20 year old house about 2 years ago, house had been empty for a few months and there had obviously been some escape of water/roof leak at some point and the plasterboard ceiling not repaired. The surveyor pointed out this was most likely a leak from the tank, but as it was now completely dry, had obviously been repaired. Surveyor noted the roof was dry (although this was summer 2018 so very hot and dry).

    However, recently, with the snow and very cold weather (-8 some nights) we noticed a leak from ceiling in about the same location as the previous damage. A plumber was working in our kitchen, he took a look and said it wasn't the pipes. Looked to be coming from the roof somewhere. Also, some of the truss' were obviously damp (some just in part, others almost completely). Water beading was evident on much of the underside of the felt (on the north facing side of the roof).

    Worrying thing is though the felt, looks to have been installed, in places, either really tight against the battens, or it's been folded in on itself. Creating a little reservoir where any water can pool rather than run off. It's this that is causing our problem I think (the felt that is dry all looks to be fine though, with a clear run down).

    The places where it looks to have been folded over, it's clear any water getting in isn't able to run off down the roof and has just been pooling, to the point that the water just sits there until the felt can no longer hold it and it starts to drip through.

    Question is, is this likely to mean a full roof job or can it be patched up?

    Some pics and video below will give a bit more detail (video is very short, but it is probably enough to see the folded felt and pooled water).



    IMG_1661.jpg IMG_1654.jpg
     
    Last edited: 14 Jan 2021
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  3. datarebal

    datarebal

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    Check recent posts on condensation
     
  4. TobyLeRone

    TobyLeRone

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    Thanks Datarebal. Having a good look through those. My first thoughts were the droplets were condensation, but then the leak through the ceiling seems to be worse when the rain is coming down.

    Still concerned about the felt that seems to have a fold in it where the water can pool. Even with great ventilation, is this always likely to be a problem?

    Cheers
     
  5. datarebal

    datarebal

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    It's not ideal, depending on where the folds are in relation to tile battens it may be easy to sort. But it may not be in which case it's roof off.

    Curing condensation is not just about ventilation , it needs insulation, correct extraction , and possibly life style change .
    Post a picture of your roof
     
  6. TobyLeRone

    TobyLeRone

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    Insulation is 20+ years old I guess, so not great, but probably okay (at least that's what the survey came back with). What could be a problem is the extraction fans in our bathrooms. I can't see any ducting pipes for these fans at all. I'm guessing they just vent into the roof space, which I guess is terrible and not going to help the situation.

    I also can't see any ventilation in the facias and soffits either. These were replaced in 2014 I believe (before we moved in), but I can't see any evidence of ventilation.

    Pics below show different views. From north and South side, plus some close ups where, to my eye, some tiles look like they've lifted. Most of the issues in the loft seem to be on the north side (pretty much the full width). South side felt seems pretty dry (relatively) and no obvious 'folds' or tight installation of the felt underlay.

    North Side - Wide view



    North Side - close up of tiles.


    South Side - Wide view


    South Side close up of flue
     

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  7. Davidandkeiley

    Davidandkeiley

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    I've had the same sort of problem in my loft space. One side of the roof was absolutely soaking looks exactly like yours the felt was literally dripping (always seems worse in wet weather) I added some lap vents and upgraded the insulation. This helped abit still didn't cure it. So I had a good look around and found 2 issues. 1 being bathroom extraction straight into loft and 2nd my boiler flue had a seal that had slipped and was allowing it to vent a small amount into loft space. Fixed both of these and the condensation cleared within 2 days.
     
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  8. datarebal

    datarebal

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    all good advice David..
     
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  9. datarebal

    datarebal

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    Condensation will be worse on the cold side.

    Get the fan sorted it probably the main issue
     
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  11. TobyLeRone

    TobyLeRone

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    had a better look for the ducting later on today and I did find it, but I can’t see where it actually goes, it’s a very difficult part of the roof to get to. I’ll need to get suited and masked up though as its crawl space only.

    Guy is coming to check the roof for damaged tiles tomorrow. I’ve got a feeling there are two issues, one is condensation and also damaged tiles somewhere. That’s the only explanation for leak to be worse when it rains.

    cheers for the pointers guys.
     
  12. ^woody^

    ^woody^

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    Droplets and the same staining on several timbers is a very good indication of condensation.

    Condensation does get worse when it rains due to the air being more humid - even inside.
     
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  13. TobyLeRone

    TobyLeRone

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    cheers Woody. The guy who came this morning was just the surveyor for insurance, no storm damage was found in the roof, but a roofer is coming next week to do a proper inspection.

    Condensation does seem to be more likely culprit I reckon. After all, the leak is most visible where the water tank is, and there happens to be less insulation where the various pipes are. Which I guess makes the path to the plasterboard much easier for any droplets to get through.

    Either way, the felt looks to have been installed either on a Friday afternoon or a muppet (perhaps both). Some looks perfect with enough room for water to fall away and a bit of ventilation, but others it’s drum tight and some places have a lovely little fold to act as a little reservoir for any water that does get in.

    I guess roofer will tell me what I need to do to remedy it. So we’ll see.

    Cheers
     
  14. TobyLeRone

    TobyLeRone

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    Quick update. Roofer came out yesterday and couldn't find any obvious damage or areas where the tiles could be leaking, although condensation was bad he said. Also, under layer felt was on its last legs and in places not fitted correctly, making situation worse.

    House is 25 years old, but tiles are not in best condition so sorting felt would really mean new tiles too. Although this isn't urgent.

    So, he suggested trying a few things to reduce condensation and perhaps installing a few ventilation tiles in the roof. Although given the size of the roof this wouldn't be cheap as we'd need so many for it to make a difference.

    I'm going to replace loft hatch as job one, an air tight version (like this https://www.accesspanels.co.uk/product/loft-hatch-metal-door-slik-44db/ or https://www.fakro.co.uk/products/al...wooden-folding-highly-insulated-loft-ladders/).

    Replace the bathroom extraction and try to fill any small gaps where pipes enter the loft.

    Does anyone have any thoughts on fitting a dMEV extraction unit in the loft? Running costs of these look to be low, and as many are humidistat controlled, they can run when needed. This would be last resort if problem still exists.

    Thanks
     
  15. SpecialK

    SpecialK

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    Can you feel any airflow when you are in the loft? Any soffit vents fitted / insulation blocking air flow?
    Loft hatch can be sorted with draft excluder for a cheaper option...

    As above make sure the bathroom extractor actually vents out. I had a newbuild where the pipe was just slung near the soffit and a vent screwed on without a hole cut! Only noticed when I emptied the water out of the hose and it didnt come out the vent!
     
  16. ^woody^

    ^woody^

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    Loft condensation is typically limited to very short periods of time when the external temperatures are low and the heating is cranked up, and this can be just a week or two over winter - it depends on the precise conditions.

    Sort the loft hatch out, and seal things up at ceiling level but an extract fan is a waste of time and no guarantee it will work (as a condensation solution) in a loft.

    Roof tiles (and felt) should last about 70 years. Exposed felt at the eaves may fail sooner, but that's a localised repair only
     
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