Weeping Chimney (Another Damp Issue)

[Slandar]

Hi All
Long time lurker first time poster, been living in a 15th Century house for a while now and there have been one or two issues.
However, have had a new one pop up that has completely stumped me following a roof repair earlier in the year we now have water coming through the chimney stack upstairs.
Before I contact the roofer I want to check with your collective experience that there is nothing obvious to you guys that might be an issue.
Appreciate the help.

 

[Cubist]

Is there any sign of damp/water directly above that beam/timber shown in the first picture?
Also, what was the nature and location of the earlier repair work to the roof?

 

[Slandar]

Hi Cubist,
Thanks for the questions.
That's not a beam but stone running the length of chimney breast (like a thin shelf). There is a small amount of water in line with where the wall is leaking, right at the join between the stone and the wall. If it helps none of the rest of the wall feels or showing new damp since it all dried out except what has appeared this weekend in that area.
We had a lot of water coming through to the left of the velux and by the chimney stack, because the tiles had failed (some were just shards). The lead around the velux was replaced, tiles relaid or replaced depending on condition and the chimney was repointed.

 

[Cubist]

Sorry but I forgot to ask about the prevailing wind direction, does this typically strike that face of the roof and chimney? Also, is that chimney in use and for what heating system?

With the very poor summer and consistent heavy rains we've seen many people have experienced problems with water penetration through the chimney stacks/flues.

 

[Stevers]

It does strike me that you'd need a modicum of luck for that set up to be adequately watertight in all conditions. The flashings on my random stonework are not stepped, but set into a groove 3" above and parallel to the roof line, and that's what I'd expect to see there, unless a CO has said no to that.

Secondly is the top of the chimney capped or cowled? One of the heavy clay lids on one of my 'elephants feet' cowls blew off (we're very exposed to the south west) just before a period of exceptionally heavy rainfall. We had water penetration right down to the ground floor, before I could get up there with scaffolding and sort it out.

 

[Slandar]

Some questions I hadn't considered before.
I believe the prevailing wind would hit the roof side of the chimney.
The chimney has a liner, and used for a wood burning stove as the house only has electric heating it tends to be in use most of the day in the winter.
The chimney has a cowl - that hasn't blown off yet
The flashing was repointed in the same places it was before so the CO hasn't said anything specifically. Is there potentially too little lining toward the top end to prevent penetration of water?
I agree it's been a miserable autumn/year so much rain could it just be one of those dry it out and chalk it up to the weather...

 

[Cubist]

Thanks for the reply and your observations. Some things for you and others to consider and perhaps add further comment and suggestions.

Although the brickwork abutting and surmounting the old rubble built chimney appears to be in good condition in terms of the bricks themselves, it is possible that driven rain is exploiting weakness or failures of the pointing. One area of particular concern should in my view be the pointed bond between that brickwork and the old rubble chimney stack. Water may be pushed through to then percolate down through any fissures and weaknesses in the mortar used in the old chimneys original construction.

In addition to the flashing Stevers mentions it would be wise to check the valley behind the stack to ensure that any flashing is in good condition and is not being over-topped by run-off from the roof above and behind it.

The old rubble chimney stack appears to be supporting a number of plants. The surface moss is not significant but some of these plants look to be a little more substantial and the roots of these will be exploding weaknesses in the mortar to continue their growth. That growth of the roots, although small, may cause damage as they seek out water and nutrients from the stack itself. On balance I think you should consider having the entire stack, rubble and brick re-pointed whilst evicting the wildlife and verify the good condition and placement of all the lead flashing.

Some people, myself included, have seen rainwater incursion down their chimneys via the chimney pots/apertures. In my case this became evident when leaks appeared around the exit of the steel flue connected to one of our wood-burners but clearly that water would otherwise have ended up in our stone chimney stack, and no doubt some of it did. Whilst cowls will help with this problem some water incursion is only to be expected unless the chinney is permanently sealed near its top.

I hope this helps,
Cheers and good luck.

 

[Slandar]

Thanks Cubist
Appreciate your observations, I will get back in touch with the roofer as it was meant to have been fully repointed and wildlife "evicted".
In the process I will get them to check the flashing in the valley.
Potentially just needs a bit of TLC