Flat Roof Leak - Help Please

rossyl

Member
Messages
3,312
Hi

We have a flat roof at the very top of our house in a loft conversion. It is torched on felt.

I'm pretty sure somewhere around the chimney breast, where the flat roof meets the chimney breast, or on top of the chimney breast, is a leak.
It is leaking onto the plaster board ceiling, not much water, but enough to be annoying.

We've called out
- a specialist roof repairer, who said he was going to seal the area, then coronavirus happened

- a roofer, he seemed alright, he burned felt on to the area that he said wasn't properly done. It still leaked, he came back and covered it in cromapol.

After the second time he came, and covered it in cromapol, the leak did lessen in terms of the amount and frequency of the dripping leak.

So I went up there and smothered it in cromapol. Covering a wider area.

But... You guessed it... It is still leaking

I'm at my wits end, as I want it fixed, but I don't want to keep paying for someone to just have a go.

I found websites of specialist who find leaks. This sounds expensive, is it?

Also, will a leak detection specialist actually find the leak?


Hoping we might have some roofers on the forum.


EDIT 1

This is how the roof originally looked, we have been told (by you guys) that's it's 'Join City' - with lots of joins and insufficient flashing.


74065


EDIT 2

We had a roofer who
"burned on" all the joints around the chimney. The leak still kept coming.
Roofer's second attempt was to cover it in Roofing Acrylic Paint. It slowed the Leak, but did not stop it.

We then did a second coat of Cromapol, acrylic roofing paint.

You can see the whole chimney is covered in Cromapol.
The bit in front of the chimney is covered in Crompaol.

A bit either side of the chimney is covered in Cromapol.


ADVICE PLEASE:

Should I
1. Try and get someone to add flashings, or has that ship sailed due to the Cromapol.

2. Go up there and cover more area in Cromapol - if so where?
I can see areas where water is pooling. I an see joins on the wall that i could maybe cover. What do you think?

This leak is really really annoying - so advice is much appreciated. Thanks

I would be grateful for opinions:


Here is what it looks like now.
Here is what it looks like now, took this today (using a GoPro on a stick) an hour after it rained


74066

74067



Thanks
 
Last edited:

allandwf

Member
Messages
10,958
From experience the leak can show a long way from the actual ingress point. Maybe worth checking structure behind the board to see if there is anywhere it can track down and along. There is a chance you are sealing the wrong area. Is the chimney in use, and in good condition? It could be coming through the chimney, maybe cap it? Good luck.
 

midlifecrisis

Member
Messages
16,102
Flashing needs to be cut into the mortar of the chimney to have any effect.
The felt could have gone porous, try using Thompson's roof seal

I've used it in the past and it really works.
 

rossyl

Member
Messages
3,312
Removing the plasterboard ceiling is something I'd rather do later.

It's really high up, and not very accessible, so I'd rather not keep trying things only for them not to work.
 

rossyl

Member
Messages
3,312
Flashing needs to be cut into the mortar of the chimney to have any effect.
The felt could have gone porous, try using Thompson's roof seal

I've used it in the past and it really works.
Cromapol is similar and arguably much better. So I've effectively used that method.

Will try and have a look at previous photos to see if I can recall what the situation is with flashing.

It's not easy to get to to just have a look.
 

2b1ask1

Special case
Messages
20,220
Ingress point can be a long way away and flashing is highly likely to be suspect. Peel the flashing up and make sure the felt extends up under the flashing at least 50mm vertically without compromise. As others said it needs to be well in the mortar too.

could it also be a crack in the chimney above all the roof?
 

rossyl

Member
Messages
3,312
Blue spot is where the water is showing on the ceiling below.

Purple area is what I've covered in cromapol.

I've not done the top of the coping stones, they look good.

Roof is 6 years old.

Since the photo was taken, the felt was burned onto the chimney stack before being covered in cromapol

73940
 

Silvercat

Member
Messages
1,166
My money is on the flashing around the chimney interface. I had a similar problem with a dormer window in my old place 36ft up the gable end wall and the builder tried 3 times to fix it. What was happening is the flashing hadnt been pushed far enough into the brick joint line and then repointed so it kept springing away and allowing rain water to run down the chimney and behind the flashing. I also found that to stop flashing springing out, use lead or soft resin wedges which you hammer into the brickwork along the joint line to hold the flashing firmly in place, then repoint. Might be worth a try. It fixed my leak on the 3rd attempt.
 

Silvercat

Member
Messages
1,166
Blue spot is where the water is showing on the ceiling below.

Purple area is what I've covered in cromapol.

I've not done the top of the coping stones, they look good.

Roof is 6 years old.

Since the photo was taken, the felt was burned onto the chimney stack before being covered in cromapol

View attachment 73940
There seems to be an awful lot of join lines in the felt around the interface with the chimney, all with potential leak paths. Is there something else you could use as flashing rather than this felt?..and preferably as a single piece cut to fit. Could lead still be an option? I reckon this might be your problem area.
 

lifes2short

Member
Messages
5,821
Blue spot is where the water is showing on the ceiling below.

Purple area is what I've covered in cromapol.

I've not done the top of the coping stones, they look good.

Roof is 6 years old.

Since the photo was taken, the felt was burned onto the chimney stack before being covered in cromapol

View attachment 73940

blimey that's a bit of a hash job, no wonder your getting a leak, who did that Stevie wonder, unless chimneys are properly dealt with then you will get water, really depends if a cavity tray was fitted in the brickwork and what's really lurking under all that felt over the brickwork, i would get all removed and then see what's there
 

2b1ask1

Special case
Messages
20,220
Blue spot is where the water is showing on the ceiling below.

Purple area is what I've covered in cromapol.

I've not done the top of the coping stones, they look good.

Roof is 6 years old.

Since the photo was taken, the felt was burned onto the chimney stack before being covered in cromapol

View attachment 73940

well immediately seeing that image Ross: the vertical ‘flashing’ isn’t chased into the brickwork so anything running down the face of the bricks or off the chimney is being directed behind the felt. You only need a needle size track for it to drip every 30 seconds.

you need proper chased in lead flashing for it to work long term.
 

jasst

Member
Messages
2,313
As others have said, that looks a total hash up, needs stripping back and a proper lead flashing chased in to the brickwork, I would also consider stripping the whole roof of that felt, and getting it done in fibreglass, using felt is a bit old school these days.
 
Messages
1,117
The life expectancy of felt roof is around 12-15 years. Rather than one by one attempts, you might consider having it stripped and start afresh with new felt and flashing.
 

lifes2short

Member
Messages
5,821
The life expectancy of felt roof is around 12-15 years. Rather than one by one attempts, you might consider having it stripped and start afresh with new felt and flashing.

a torch on 3 layer system if properly done can last in excess of 20 years, the felt on that roof looks perfectly fine, its the cr4p job around breast that's the problem here
 

Simon1963

Member
Messages
819
As there have said have it completely re done around the chimney. Perhaps take off the coping stones and flash under that in lead and into the chimney rather than over it.
 

rossyl

Member
Messages
3,312
Balls.

So it sounds like I might need to do some proper flashing around the chimney breast and coping stones.

I've no idea how to do that. Nor do I know how much it should cost.

Any thoughts are appreciated.

Also, any recommendations for a roofer in North London