Damp in chimney stack

[yjones]

I went up to the loft the other day and noticed damp patches on the chimney stack:

What could be causing this? The pointing in the chimney stack above the roof line? The chimney pot has a cowl on it. All the cob around the stack is dry - its only the dark bricks you see that feel slightly damp to the touch.

Thanks.

 

[KenGMac]

yjones, good evening.

OK there is a cowl but is the flue or flues in the chimney in use, or dormant? are there any vent terminals within the rooms? if the old fireplaces are blocked of?

You will have to get up close and personal with the chimney head to ensure that the pointing is indeed intact?

There appears to be on the image posted a "damp area" on the right hand side [as seen] which is it appears the full height of the internal area of the chimney breast, such a marking is indicative of a problem with the lead flashing between the chimney head and roof tiles or slates? I assume that there is a lead flashing or is it a cement flashing in this location?

You can sometimes see the lead flashing from the ground using a pair of binoculars or similar?

On numerous occasions I have seen the lead flashing as above being stuffed full of dirt and debris, the dam of dirt Etc. can allow rain water to rise above the level of the flashing and enter the property?

 

[bobasd]

op, why not post photos of the outside stack an stack flashing.
if you can, photos of the flaunching an pots o top of the stack as well.

the streaks mean thers been leakin previous - maybe still is?

have all the flues been swept an ventilated top an bottom?

whoever fitted the membrane underlay has done it wrong at the chimney breast - it sshould roll up behind the flashings, not drop down.

the rafters are undersized for that span an buckling - two log purlins have been inserted.
the supportin post for the lower log purlin could split an thers no sign of any fixings to the waney rafters or the post - its all relyin on gravity - thats bad news.

 

[yjones]

Thanks guys.

Heres a photo I just took:

Ill take some more photos tomorrow if I get back from work before dark.

To give more detail:
Its a shared chimney (fortunately I own both sides). Both sides are recently fitted woodburners (HETAS certified). So the damp cant be caused by rain coming through the cowl (unless the flue liner has split which is very doubtful!)

So its either the flashing, pointing or flaunching(?)

As I say, Ill try and take some better photos over the next 2 days.

Many thanks.

 

[Leofric]

The abutment of roof to brick chimney stacks usually have stepped lead flashings .

 

[KenGMac]

yjones, good evening again.

The lead flashing between stack and roof as above is best done as a stepped flashing, yours may be into a raggle, but the image posted is not clear enough to see accurately.

In some cases, the lead is simply butted up to the stack and mastic is the only barrier against rain penetration, over time the mastic fails and the rain gets in.

As for the flashing along the "back" of the stack??? it appears to be wrapped around and nailed in place?? not a good omen?

From the image posted there are it appears some areas of missing mortar?? and at least a couple of spalled faces on a couple of the bricks.

Any other images may assist?

Ken.

 

[Leofric]

'The lead flashing between stack and roof as above is best done as a stepped flashing' - wish I had thought of that Ken !

 

[yjones]

Thanks all. I will try and take some more photos over the next few days. Problem being is it will be dark before I get back from work. If not Ill take some at the weekend.

 

[KenGMac]

Leofric, good evening.

You did think of of it and as I posted---

as above is best done as a stepped flashing

Safe to say we both agree on what would be best practice?

yjones

If possible more images and see if you can increase the pixel size of the image problem is the large image may not upload to the site.

Cheers.

Ken

 

[^woody^]

The pointing is crap.

 

[cwhaley]

Best to get up there and have a closer look I think. Can only see part of the chimney and flashing from the ground and we can't see the condition of the chimney crown at all.

 

[yjones]

Hopefully these photos show a bit more detail.

Does the pointing look that bad that it would make the chimney breast damp?

Does the flashing look like it has mastic on, which is perhaps falling away. If so the water could be getting in behind the flashing.

What possible costs am I looking at for:
a) re-pointing the worst bits
b) re-flashing

 

[KenGMac]

yjones, good evening again.

Images posted above assist a lot, they can be enhanced and brightened up as well.

Several things.

1/. in the last posted image, there is a lot of "vegetation" [ferns] growing out of the mortar joints, never a great sighn, the ferns need to be totally removed?

2/. I the first posted image, there appears to be a lot of missing mortar on the right hand side near the upper [back] end of the side of the chimney, the position of the missing mortar is close to the line of the lead flashing, this will allow rain water an entry point?

3/. In image one posted there may be a load of debris built up between the lead and the slate ?

4/. The images posted appear to indicate that there may??? be two layers of lead, one stepped. the other may?? have been run over the top of the stepped lead flashing?? as seen in images 2 + 3 this could indicate historic problems with the flashing's, hence the need to insert the second flashing over the first??

5/. The cap, the "topping" to the stack appears to be thin? could be a skim of mortar only, this can crack and admit rain?

6/. There appears to be lead wedges that can be seen at the top of the lead, where it would appear that the lead has indeed been tucked into a raggle formed in the brick [the wedges jamb the lead into place to assist in holding the flashing's in position] however, some pointing appears to be missing at this raggle.

In general terms an overhaul of the stack would not go amiss, a general good rake out and re-point, at the same time a good look at the flashing's would be a necessity

As for costs?? depends where you live in the UK

Ken

 

[yjones]

Thanks Ken, very informative. Whoever I get in to look at the chimney Ill show them your post so they have a starting point.

re Costs: Im in the South West. Are we talking hundreds or thousands?

 

[yjones]

I dont think Im adding anything new here, but Ive just taken a photo of the same chimney breast the other side of the wall. A similar situation, although perhaps not quite as bad. Obviously being a shared chimney this was to be expected.