Baffling Roof Leak

[ACL]

So I've a stone terrace, c1900. Roof has been updated as it has a breathable membrane. I've had the chimney stack re-pointed and new lead flashing/soakers done. Im still getting water leaking into the loft down the wall where the chimney stack is, it drips heavily from the sockets of both purlins. Only happens when I get heavy rain. It's dripping not just soaking through via osmosis. Flaunchings have been redone and all chimneys have been capped. 
Any ideas?

[ToughButterCup]

Photos would help us devise a strategy with you.....

[ACL]

[Marvin]

Is that a gable end?

[ACL]

no, it joins with neighbours house. its where the chimney stack is. 

[Redbeard]

Is the stack within the thickness of the party wall? I can't see a 'chimney breast'. Can we have external pics? How does the purlin socket line up with the edge of the stack, for example? Can we assume it is about on the bottom side of the stack? If so, in the absence of any other 'hypotheses' so far, can I throw in porous stone effectively 'by-passing' the flashings and soakers?

 

Have *you* had the roof re-done or was it like that when you bought the house? Did you have exactly this same problem before you had the pointing, flashings and soakers done?

 

A bit unlikely, but could water be getting (in some volume) *inside* the stack, soaking the wall and transferring through. I assume you had the flaunching done at the same time as the other works?

Edited Friday at 11:14 by Redbeard
Add re flaunching

[Marvin]

Does the chimney pot have protection from the rain going down the chimney?

 

Is the cement capping at the top of the brickwork all sealed with a waterproof layer? 

 

 

[ACL]

Thanks for the replies so far. Pics incoming but to answer your questions:

 

the purlin sockets do seem to line up with the edge of the stack. the chimney breasts is within the thickness of the party wall. 

 

I haven't had the roof re-done, but there is a breathable membrane indicating it has been done in modern times. 

 

When I bought the house there was signs of leaking in the same spot, which is why I did all the work I've done so far, thinking it would rectify it. 

I did notice, since the flashing and leadwork, the leak appeared worse than before. it was a trickle before, now it's more like a steady stream. 

 

Flaunchings were re-done when I had a wood burner fitted as it needed lining and a new pot fitting. 

[ACL]

[Marvin]

12 minutes ago, Marvin said:

Does the chimney pot have protection from the rain going down the chimney?

 

Is the cement capping at the top of the brickwork all sealed with a waterproof layer? 

 

 

Also how many chimney pots.

[ACL]

16 minutes ago, Marvin said:

Does the chimney pot have protection from the rain going down the chimney?

 

Is the cement capping at the top of the brickwork all sealed with a waterproof layer? 

 

 

the pots have been capped, flaunchings have been done. by done, I mean they've been re-cemented. I dont think they knocked it all back and added any layers 

[ACL]

3 minutes ago, Marvin said:

Also how many chimney pots.

4 pots. 

[Marvin]

Thanks for the pictures. It helps for us to guess what is going on.😂

 

Hmm. A few things that I would consider:

 

Do your neighbours have the same problem?

 

Is the leak greater when the rain is driving towards your side of the stack or your neighbours?

 

I have had flaunching absorb water, also the seal between a pot and flaunching can leak but not usually that much.

 

However,  as you have so much coming through I wonder if the breathable membrane continues over the party wall or if there is a bad join over the party wall.

 

However, as the leak is worse since the remedials were done, it could be a problem is to do with the remedials or that the remedials stops the rain from being absorbed earlier on and its channelling it to the purlins.

 

Hopefully these ideas will help.

 

Not a nice way to start the new year.....

 

M

 

 

 

 

[ACL]

yes, the leak only appears when it rains heavy and seems to be when the wind direction is blowing it right onto the side of my stack. 
looks like next step is to start finding out where the membrane ends. 

[ToughButterCup]

How about water leak detection tablets - dye the water in one area ( in this case  a limited area on the side of your chimney) and wait .....

I've used my  Thermal imaging camera to discover leaks before now - the water lowers the temperature locally

 

I'd be tempted to take this short plank out and have a little look-see.....

[jfb]

I’m no expert but if mine I would like to know how much overlap the lead soakers have. There are little gaps where wind driven rain could get in but the overlap should cope.

Also the section right at the top where there is no lead over the ridge tile looks a weak point to me. I appreciate that your leak seems to be further down but maybe it is tracking down from higher up. You might be able to test this by sending a hose right where the ridge tile meets the stack and see if any is getting inside.

[mjc55]

Why is the lead under the tiles?  It should be dressed over the tiles (unless I am missing something!)

 

Any rain will run under the tiles and eventually find its way inside!

[Redbeard]

The lead under the tiles is (are) the soakers, AFAICS, laid as you'd expect as per the slates (I think). There is then a sort of 'mini-skirt' flashing over the upturned soakers, again, as far as I can see. Although the abutment is different that's how the soakers work on my extension abutting the main house wall with ridge at 90 degrees to the main house wall. My 'cloaking' (over the soaker upstand) is different in that it's a thinned-out layer of EWI, and comes down further, but the principle is the same. The practice is different in that mine does not leak...

 

Looking at it again we used to allow a 150 upstand for soakers and stepped flashings and bottom and top 'aprons'. Do we think rain could be 'bouncing' over the lead-line, soaking into the sand/cement 'fillet' and running down? (Not certain I buy that even though it's my suggestion, but 'discuss'!).