Chimney leaking - dripping from DPC into loft?

[trickadero]

Hi all,

I've got an issue with my chimney I'm looking for some advice on. Property is a 90's build which we've recently moved into. Poking about in the loft late Autumn I noticed damp on the rafters/joists around the chimney. The chimney construction is per the below, though there is also a DPM in the chimney brickwork below the felt line (second pic - visible just below the batten).

I've been up several times in the rain now and it is clear (though perhaps not from the picture) that the face of the bricks above the DPM are wet which then pools on the DPM and drips onto the rafters/joists. Bricks below the DPM are bone dry. As you can see it can get pretty wet in heavy rain..

A roofer has taken a look and ultimately made three visits (on the original quote to his credit). First visit he re-fixed the flashing, second time he removed the tiles/inspected the felt/repaired a pin prick in the lead gutter, third time he coated the chimney in water repellent. He says the flaunching, pots/caps and pointing is all OK.

Unfortunately the leak remains and if I engage him again it'll be for more significant work. I'd to go into the next conversations more educated with wider opinions/understanding behind me.

So what is causing this and what's the best approach to resolution? Re-point and re-flaunch to see if that fixes it? Is there something fundamentally wrong with the construction?

Other points worth noting. The house is unique in the area bar a mirror on the other side of the street and that chimney doesn't apparently leak in the same way (albeit elderly owner so perhaps not exploring the depths of his loft regularly). Secondly there was a large dead wasps nest in the loft to the corner of the chimney (do wasps like to burrow in pointing?). Finally, the chimney isn't in use, but I couldn't say for how long for certain beyond about 4 years.

Apologies for the long post, thanks for bearing with me!

 

[^woody^]

Normally this is a sign that the lead back gutter needs renewal.

Lead work is specialist. Be sure it's within the roofer's competence.

Hasn't the roofer taken any photos?

 

[trickadero]

Thanks Woody,

He did when he refixed the flashing and showed me at the time, but perhaps not of the gutter. I'll ask if he can dig them out as it was a while ago

 

[tel765]

I cant clearly make out whats going on in your pic but I can see some possibly serious issues with wood rot.
From what I can see its doesn't seem that your sketch matches the actual back gutter - they are not the same?
If you've been going up on the roof then why not go back & take some pics - and some better pics in the loft, & post them on here?

The DPM you refer to - do you mean: A DPC lead Chimney Tray?

 

[trickadero]

Thanks tel,

I think the wood is sound, admittedly on that pic it is sodden, but fortunately it gets chance to dry out rather than being permanently wet. There's the remnants of a wasps nest to the right of the picture which also confuses things.

The back gutter isn't visible from inside the loft and it's really not possible to take a better pic than the one I've posted. I haven't been up on the roof myself and would prefer to avoid going up ladders, but I've asked the roofer if he can dig out the pics he took and will post if he replies.

By DPM I really mean DPC... black plastic (LDPE) inserted between courses of bricks.

 

[tel765]

Where is this plastic DPC located?

 

[trickadero]

Below the felt/tile/lead level.

You can see it in the picture just below the central batten.

The issue is above this though, either water getting past the flashing and running down the brick faces or just seeping through the bricks themselves. It reaches the DPC and pools/drips onto the rafters/joists.

 

[tel765]

I'm not criticising but telling you straight that from what you've said & shown - and from what i can make out, that not much makes sense for a 1990's build?
Ditch the roofer & try and find yourself a professional roofer who, as above, understands leadwork and presents you with before and after pics.

 

[stuart45]

It should have a lead tray with the back and sides dressed up, front down and weep holes at the front.

 

[KenGMac]

What state is the exposed brick work above the roof line? does the mortar look to be in good condition?

 

[trickadero]

Thanks all,

Original roofer cannot find the pics he took and has asked I get someone else to take a look so there's a couple of different firms coming round over the next fortnight. After describing over the phone both have suggested likely solution will be flashing or sealing the brickwork, although the original roofer did both of these without resolution.

I've taken a pic externally from ground level so apologies for the low quality. There's no lead tray/weep holes as far as I'm aware, just a lead gutter and the plastic DPC. There is a lot of chimney and the rain tends to drive into the roof side due to prevailing winds plus we're in quite an exposed location at the top of an estuary.

 

[KenGMac]

Is the chimney in use? if not consider having a vented rain cap installed when roofers pop along?

The cap could assist in rain penetration at the chimney pot and reduce overall the volume of water getting "At" the chimney.

Ken.

 

[Nige F]

Normally this is a sign that the lead back gutter needs renewal.

Lead work is specialist. Be sure it's within the roofer's competence.

Hasn't the roofer taken any photos?

There is no proper back gutter - it should be higher up the chimney and discharging onto the tiles from above them

 

[tel765]

There's a definite back gutter but the flat bit (the solum), if its there it cant be clearly seen. There's no supporting boarding in the pic - only unsupported lead.
The back gutter is not a conventional one-piece back gutter. It should be replaced?
Maybe the tiles directly above the back gutter needs altering to give the correct cover?

The stack, for a 1990's build is in poor condition - the pointing is failing, and it appears to have been bleeding "contaminants" to the smoky surface. I'd put a bet on the flaunching being shot.

The cause of earlier confusion can now be seen - the roof pitch changes plane above the back gutter, & the roof was then framed & trussed to suit the change in plane?

OP, you will need to have the area behind the stack stripped and re-done properly.

 

[Barthy]

It's called a sprocket tel not that I expect you to understand the importance of one of those. I'd stick to lego and your black and decker tool kit mate.