Chimney saturation leakage

[Rjtaylor1980]

Hi all,

For 3 years I've been battling a damp issue in the chimney breast area of an upstairs bedroom.

If I could turn the clocks back I'd have knocked the stacks down and built new ones as so far I've probably spent around £3k and still not having success.

It's an external stack that is quite exposed with little protection from the elements.

To date, I've:
Installed new lead flashing
Repointed
Washed stacks with liquid waterproof sealant
Replaced cracked bricks

Leak continued.. But point to note is that the leak only happens with driving rain hittiing the roof side face of the stack. If the rain falls vertically I rarely see issues in the room upstairs.

Over the winter I've had the stack covered in a plastic sheet and not has a single issue. Following this trial suggestion is that the issue is saturation leakage. When the rain hits the internal face of the stack, bricks are absorbing the water which then migrates down the stacks, and as the plaster in the upstairs room is old lime, it acts as a sponge and brings the water in to the room.

Trades are all giving me different advice at this point and I'm not sure what to do....

Options.
1) clad the rear / half the sides of the stack in sheet lead to protect the bricks from the rain
2) blow torch felt to the rear face of the stack
3) entirely render the stacks
4) don't do anything to the stacks as the bricks need to breath... Intead replaster the room. Either baton the existing wall and re board / plaster. Or remove old plaster and paint bricks in tar to give waterproof layer and replaster.

My issue with 4 is that the water is stil coming in... I just can't see it.

Any advice from any experts on this who may have seen it before is highly appreciated.


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[stuart45]

Sound like they need a lead tray installed which does involve rebuilding some of the stack.

 

[Rjtaylor1980]

In an ideal world, yes they do.

But I'm trying to find a way of not spending about 4k and in doing so knocking down another 3k of work....

House is 1930s. No lead trays in any stacks for miles around here (except a few new builds) so hoping their is another way.

 

[stuart45]

Render can sometimes help, although when it cracks it can still let water in.
Lime render with NHL is getting more popular these days for older properties.

 

[ree]

Have you had the flues swept? Its possible that the damp thats presenting in the room below is coming from sulpherisation in the flue soot.

Pics of the "external stack" (all stacks are external, do you mean an external chimney breast) would help.

Have you examined the chimney breast in the loft during & just after rain? Take pics of any staining.

read back posts on here ref this issue - use the search button.

 

[tombodge]

Ive got this problem.

I thought i was just going to have to re cap the chimney. The chimney has been re pointed and ive just had a new roof so the flashing is good.


The only place I could think it was coming in was down the inside of the chimeny its self and then socking though the brickwork as it happens where theres a kink in the chimney

 

[rjtaylor]

Thanks all for your replies.

Some pictures as requested.

The water damage:

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• rjtaylor
• 15 Mar 2015
• 1

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• rjtaylor
• 15 Mar 2015
• 1

The stacks:

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• rjtaylor
• 15 Mar 2015
• 1

So yes, external breast....

This is a pic of a chimney on a local new house. Yes, it has lead trays which I couldn't do without a rebuild but it has the lead sheeting at the rear of the stacks which I was thinking may solve the problem (would need more lead than the chimney pictured as would need to go 3/4 of the height of the stack...)

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• rjtaylor
• 15 Mar 2015
• 1

Haven't had the flues swept. There are 2 flues in the stack. One to the ground floor room (which had a gas fire) and the other to the upstairs bedroom which has previously been bricked up and ventilated with an air vent. So wouldn't be able to sweep this unless I open up the fire place. I have been considering this just to increase ventilation if I thought it may solve the problem??

Thanks again.

 

[rjtaylor]

Oh, and no damp found in the attic during rain. The loft structure makes it very hard to get access to it so I even drilled a big hole in the ceiling of the bedroom close to the brickwork to assess for damp and found no sign.

Even found a wasp nest there and they wouldn't go near damp.

 

[ree]

Thank you for the pics.
But if the scaff is still there, why not go up and take more pics showing the flaunching and flashings on both stacks?
Why do you have scaff there?

So you have two stacks, and two terminals (visible in the pic) both terminals are fitted with Colt air vents. The Colt gas vents have "higher" screens but these will work with a gas appliance.

Lead DPC trays are not much use on external chimney breasts - rain water will keep by-passing the trays on the external exposures. Sound pointing at 20mm depth is best.

The old flaunchings should have been completely removed, & new flaunchings applied. The new flaunchings should be sloped to shed water.

Each flue should have a separate Pot/terminal for ventilation - and to give the stack a balanced look.

The pics of the damage in the room (s) below looks like pure water damage but without pics of the stack back gutters, flashings & flaunchings as they look right now, its impossible to accurately advise.

All your flues must be swept or sulpherisation will take place.

Any notions of installing lead cover flashings higher up the stack, as in the other house pic, is unnecessary, simple step flashings & soakers will do. Likewise, any kind of rendering is unnecessary. Rendering is always a last choice.

 

[rjtaylor]

Thanks for coming back to me.

Pics were taken some time ago and scaffolding has since been removed. It was erected to do a full repoint of both stacks.

I've also has flaunching removed and redone, as well as correct ventilation of the unused bedroom flues. See pic from this morning:

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• rjtaylor
• 16 Mar 2015
• 1

As you can see, the rear stack has been sheet covered all winter ( is was taped shut on the left side but wind has got behind it and blown it open). As I said earlier, since doing this trial I haven't had a drip enter the house...

So while I can't take pics of flashing it surely can't be this on the back of the trial? This is why my mind is leading to me saturation of the bricks.

 

[ree]

Couple of things:

How do you intend to remove the plastic sheet from the stack? Whoever goes up could possibly use a camera?

Venting the flues is good but not good enough. The flues must be swept.

If your evidence of moisture penetration is merely stains then how do you know that "not a drip has entered the house"?

You also have render which is notorious for allowing moisture penetration. Your external chimney breasts are rendered.

 

[rjtaylor]

Thanks again.

I'll try and get some pics when the sheet comes down.

How do you sweep the flu of a bricked up fire place?

Evidence is not just stains. See the first picture of the water damage. I physically get runs of water falling down the lining paper. The paper has been so wet its bubbled off the wall. The staining is dried up water marks. I've had no running water on the wall since the sheet has been in place.

As stated earlier, I only get issues with driving rain. When the problem occurs the rain is hitting the roof side face of the stacks (so wind bringing the rain over the top of the house). So the rendered stacks lower down are completely protected when rain coming in that direction. I can't believe this has anything to do with it.

 

[ree]

You open up the fireplace its the only way - often there's rubble piled up inside.

After sweeping and cleaning out then you can brick up and leave a hit and miss vent installed or whatever opening you wish.

 

[noseall]

Have you explored hygroscopic salts as the cause?

 

[rjtaylor]

As I said earlier, I have running water rolling down the wall when it's heavy rain so it's not just a stain.
So discounted hygroscopic salts as a cause...