Garage Felt roof - water coming through mortar

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Established Member
2 Dec 2020
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Tyne and Wear
Hi all, just looking for advice on an issue with moisture penetrating through the mortar in my garage. It’s only in a certain area of the garage and it seems to be at the exact height that the utility room is attached externally, where there is some flat felt roof which runs off too the guttering.

I can’t see any obvious damage to the felt but I’m wondering - does this kind of roofing material stop being waterproof over time, and could the water just be penetrating through it and through to the brick?
Is this easy to replace/repair as a DIY task if that is the case? I was wondering whether it can just be painted over with the black bitumen type paint to reseal, or whether you need to put that underneath and replace the felt itself?

Added some photos to try to show what I’m talking about.

any advice appreciated


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I cant honestly tell from the photos what the 'flashing' is..... is it definitely roofing felt??😲
It could also be fibreglass, but generally, it would ( traditionally ) be lead. Fibreglass would be fine is correctly laid up and finished ( roofers often use a grey gel coat over fibreglass matting impregnated with resin )

You need to find put what the flashing is.... how long ago was that roof done?
It’s not lead flashing - I know what you mean though, the way it’s been sloted between the bricks makes it look like it. I’m fairly sure it’s felt, that gritty finish stuff that you get on top of sheds? I’m no expert though, could be wrong. No idea how long, but I’d imagine it was gone when the previous owners bought the house so around 11 years I think.
No its definitely not lead, but i was hoping it was very rough fibreglass.... which would be fairly stiff when pressed. Roofing felt is not used for flashing... it deteriorates quicker when exposed to sunlight and constant weathering. Generally old felt covered with tiles or slates etc becomes brittle, but felt exposed to sun and weathering etc can deteriorate fairly quickly. So basically if its felt, you'll need to take off the courses of slate and replace it with lead or fibreglass.

Theres also torch on felt, which is thicker and gets stuck down using heat. Its possible they used that, it would be an extremely shoddy job to use the old style normal roofing felt there..... torch on lasts about 20 years, so you would still be looking at kead or fibreglass. Torch on is now more expensive than it used to be because the insurances for the roofers are astronimical, so I'd expect lead or fibreglass to be the best bet
Thanks for the replies. I was sort of hoping it was something I could do myself (brush on some kind of sealer) but I guess maybe it’s best to get it looked at
Also looks like not enough fall, so water sits on it too long instead of running off
You might get away with painting stuff on for a while. I guess it depends if it matters that the shed wall gets wet.... if not such a big deal, try the paint on bitumen for a short term fix.

As jacob rightly pointed out, when the final fix gets underway, try to inrease the fall across the back of the chimney
thanks - I also thought this, doesn’t seem to have enough slope to run off. I can see after it rains that the felt (assuming that’s what it is) soaks it up, which is the darker part on the first couple of pics, so am thinking it’s just lost it’s waterproof quality and the paint on stuff might be a temporary fix.
So many of those paint on sealants to choose from!
Obviously difficult to tell exactly off of the photos but, in my opinion, it looks very much like a repair I’ve not long completed on my cousins house. Their slate roof/lead valley junction was crazily difficult to get to (because of the position of a lower lean to) and so I could only offer to try a short term fix via a ladder……I used a combination of flashband and the paint-on fibre reinforced bitumen - it has worked (not sure how long for mind you) BUT the result looks EXACTLY like what you have, including the horizontal ‘lines’ - created by the brush strokes. In other words they now have a lead flashing that doesn’t look like lead.
Thanks - it doesn’t look like anything has been brushed on or there is any fibreglass. I may try and get some better close up photos and post. The dark horizontal lines are the water where it’s soaked in and not dried out yet.
I think I’m going to try a paint on sealer to see if it dries it out in the short term and maybe have a roofer look at it next year. That stuff I’ve linked too says it can be used on wet surfaces even, so hopefully should work out temporarily