Will Masonary sealer cure damp? (Ed.)

[MacLaverty]

Next week we are getting a roof replaced as its leaking like a sieve. The house was built in 1901 and still has it's 2 original Yorkshire stone chimneys. We are having issues with a damp chimney breast where the chimney bricks under the roof line are wet after heavy rain, mold starting to form on the internal structure and salt deposits forming on the bricks. Whilst they are replacing the chimney flashing, soakers and repairing mortar etc, is it worth them applying a layer of masonary sealer to both chimneys to stop rain soaking into the masonary or do these chimneys need to be able to breathe and sealing them would make the issue worse?

Previous owners have replaced the original fires with gas fires and both chimneys are capped at the top. There doesn't seem to be any air vents installed on the chimney itself but only the rear one seems to be getting wet during rainfall.

 

[aveatry]

I had a similar issue and it was the leaking flashing so if yours is being redone it should be ok after. Yes I too have read stuff about waterproofing sealer actually sealing in the moisture.
I re set my flashing as it only had a small lip into the brick work so I took out the old mortar and then resealed with lead mastic under the lead lip then fixed the lip in place as mastic squished out and then filled the mortar line with more mastic. I also repointed the rest of the mortar after raking out a lot and I used waterproofer only on the new pointing. The top is capped with an air gap and there is a vent in the blocked off fireplace below.

 

[MacLaverty]

Ah ok, fingers crossed it sorts itself once the roof has been replaced!

 

[Laurieo]

When you say capped at top ,do they have proper gas fire chimney pots .

 

[tomm12]

No, it wont cure damp. In some circumstances it might make things worse. Without seeing the top of the stack cant say much about it.
The back gutter looks to be a poor installation and is possibly leaking.

 

[MacLaverty]

So the entire roof and leading is being replaced next week so back gutter and all chimney soakers and flashing will be renewed. Just wondering if it's wise to get the chimney stack sealed at the same time to cover all eventualities?

 

[MacLaverty]

When you say capped at top ,do they have proper gas fire chimney pots .

Very bad picture but these are the pots. Only one flue is live but got them both capped.

 

[foxhole]

Essential the flues are ventilated to keep dry .

 

[aveatry]

Very bad picture but these are the pots. Only one flue is live but got them both capped.

I think from that I can see when you say capped there is an airgap but watertight. I would also get them to compleatly repoint the chiminy whilst the scaffold is up and after all that all your problems should go away. But I think you do need a vent in the blocked up fireplaces so air can flow up the stack.

 

[Ivor Windybottom]

If you're re-roofing anyway then you could consider taking it down, roofing over and putting in a new standalone gas flue. Save a load of future messing about and doubt.

Quaintness is nice just as long as it's not at the expense of water running down your walls.

It's possible that the issue is that there's a run of roof sloping towards the chimney. This is why most chimneys are at the top of a roof.

 

[MacLaverty]

I think from that I can see when you say capped there is an airgap but watertight. I would also get them to compleatly repoint the chiminy whilst the scaffold is up and after all that all your problems should go away. But I think you do need a vent in the blocked up fireplaces so air can flow up the stack.

Yeh they were capped about 12 months ago and no issues really till now on that chimney. At the moment the roofer is planning to have a check over the pointing and do repairs but should I ask for an entire re-point? How much extra time does this normally take considering I've got 2 chimneys of the same size?

 

[MacLaverty]

If you're re-roofing anyway then you could consider taking it down, roofing over and putting in a new standalone gas flue. Save a load of future messing about and doubt.

Quaintness is nice just as long as it's not at the expense of water running down your walls.

It's possible that the issue is that there's a run of roof sloping towards the chimney. This is why most chimneys are at the top of a roof.

Unfortunately I can't take them down as the chimneys, we have 1 front and 1 rear, is shared with the neighbours otherwise I would . But both chimneys are the same and only the rear one showing damp and wet bricks. Hopefully once the flashing is re-done and pointing repaired it should be much better. Just not sure whether to do masonary sealer at the same time to ensure the brick doesn't soak up the rain?

 

[aveatry]

Your wet brick does look like soaking water, the problem i had was i could see it dripping down the stack in the loft and once it stopped raining it dried without a trace yours seems to be wet all the time or at least very slow to dry - like its coming from the inside of the stack, perhaps rain is getting down the non flu sleeved part of the chimney through bad or missing flaunching at the top. In which case sealing the outside will make matters worse.

 

[MacLaverty]

Honestly I have no idea really what's going on, it only really happens in heavy rain from what I can tell. The bricks aren't wet to the touch so are drying eventually. As part of the new roof I'm increasing ventilation to that part of the roof so hopefully that speeds up drying time if it does keep getting wet. The flaunching only got re-done about a month ago so hope it's not that. Going to get the roofer to check all aspects of the chimney. The rear gutter on the chimney has been covered in rubber so that can't be a good sign. Hopefully once lead has been replaced and re-sealed it will help the issue!

 

[aveatry]

Honestly I have no idea really what's going on, it only really happens in heavy rain from what I can tell. The bricks aren't wet to the touch so are drying eventually.

That's what makes me think it is coming from inside as mine were wet and I could see the drips rolling down heading for the bedroom ceiling.