New felt roof, recurring flashing leak

[Alastairreid]

Im from west lothian, i could have had a look for you.

 

[Kaymo]

Thanks Alastair, will PM you, but there is not really much to see. There are no visible gaps in the flashing, or the pointing/stonework. The leak only appears after the wall has been soaked in a particular place for about 20 minutes or so which is what is making it so hard to resolve

To be honest I don't believe it is coming through the flashing anymore. Even if it was still coming through after the raggle was resealed and cemented, I can't see how it could come through that and a layer of continuous bitumen. Having said that I agree with those who have suggested that the lead flashing would be a better longer term bet and I am following up with the roofer on this.

I've now painted some sealer on to the mortar and sandstone in case it is coming through there, and will try again tomorrow once that has had a chance to dry.

 

[fixitflav]

Morning all, hope you are well and staying sane in these crazy times. Sorry, below bit of a long story but wanted to include all the details.

I have had a new felt roof on flat roof of extension, which is built on to a 200 year old sandstone/whinstone house. Keep getting a leak on one section of the flashing (not sure if that's what you call it when its felt). Roofer came back out and replaced that section. He thought that it was getting in behind the joint due to crumbling parts of the stone so also dug some of this out and cemented in that section after replacing flashing and used CT1 in the joint between felt and stone.

However, it is still leaking. Its a small leak, and it takes a lot of water to get it to happen, and as its running down the old wall I wouldn't even know about it if I hadn't opened the ceiling inside to put insulation in (I saw a damp patch and checked with a hose to see if it was residual). Having said that, I don't want to fill a void with insulation where there is even a small amount of water coming in.

The roofer has offered to come out again and trying cutting in a bit further up, but not sure I want to just keep doing this and hoping for the best, I'd rather something more conclusive so that I can close up with confidence.

Once thought I had was to put a render fillet above the flashing tapering away from the stone and covering the felt. Not sure if this would work. Another was to cover where the leak is with a bitumen mastic or some other product where I could make a fillet that would push the water away towards the roof.

Anyone have any advice?

View attachment 187782

I had a leak in a flat felt roof, about 30 years old. Cracked where it bent up on the raised surround. I got a tin of Evercryl, link below. As well as filling the crack I stuck a length of felt over it. Cured the leak and I was well impressed with the Evercryl. Maybe a coat or 3 of that will solve your problem.

Evercryl Fibre Reinforced Roof Repair Compound 5Kg

 

[Kaymo]

Thanks Fixitflav. I had effectively ruled out the flashing in the end with the bitumen and mastic. It couldn't be coming through that. My belief now is that after the roofer repaired the original leak the lime mortar was saturated from all the testing to find it in the first place, and subsequent soaking to test the repair. I think that what was happening was that with the mortar saturated, adding more water was pushing it through on the other side. Maybe if the raggle was cut deeper this might not have happened, and in the long run I think a proper lead flashing would be better. I have offered to pay for the lead if the roofer comes back and fits it.