Damp patches in chimney breast

[nick_noal]

Hi everyone, I’m looking for some advice on the best course of action to fix a damp patch that is around 1.4m high on a newly plastered wall.


So the entire house has had a damp course recently. The damp plaster was removed up to 1.4m high then damp injections and a damp membrane was fitted to the wall before new boards and skimming was done.


Unfortunately I didn’t knock off the plaster on the entire wall and just removed old plaster to around 1.4m high and skimmed the entire wall instead.


I now have some strange damp patches on the chimney brest wall that is in the exact spot where the new plasterboard would have met the old plaster (see attached image).


At first I thought it would be the chimney needing capping off, however the damp patch is midway down the wall rather than damp at the top of the wall which is normally the case with an open chimney that is letting water in. The highest points of the wall are completely dry.


I’m wondering whether this could be caused by damp bricks that need to dry out and so am considering hiring a dehumidifier, but would appreciate any advice before doing this?


Thanks!

 

[nick_noal]

Here is another picture of the damp patches. It looks like the “dotting and dabbing” hasn’t dried out but it’s been like this for months now.

Thanks

 

[Dirtmechanic]

Sorry the convolutions of water are so complex and your up close pictures are very clear but no way I can even begin to surmise what the source is or any of that via thise pictures. Its obvious water comes from outside the building however and your picture do prove its wet inside.

 

[nick_noal]

Thanks, I do understand it is hard to diagnose just from some photographs.

Would you agree that it is unlikely to be the chimney allowing water in? As can be seen in the 2nd photograph, it is dry above the wet patch. Therefore would I be right in assuming it can’t be the chimney as the entire wall would be wet starting from the highest point?

Thanks

 

[Dirtmechanic]

So from the metal cap atop the flue downwards there are often cracks in the masonry cap, and if so a vinyl or latex improved masonry layer is often applied atop the broken area. Then you are off to see about any mortar pointing cracks in the brickwork, As to the roof and chimney connection there is a metal flashing which when done by serious folks will be not just glued on with roof patch or silicone but literally inserted into a groove cut with a diamond sawblade where the metal is imbedded with adhesive into the masonry whereby no water gets behind it. Then there is the wall to chimney connectivity which is often just caulked. Any or all of these points can deliver water inside.

 

[nick_noal]

Thanks for the advice!

 

[Retired]

Hi,

Obviously with the damp patches remaining for months water is getting in from somewhere; DirtMechanic has covered most of the areas that could be at fault.

I'm concerned though that you are unsure about your uncapped chimney being at fault; this would be the first place I would inspect; pictures of your chimney might help; what kind of chimney stack is it; brick or stone? is the chimney lined because water could run between chimney and liner; is the chimney pointing in good condition not that this should really be the cause if the top of the chimney is open to the elements but if the chimney is lined I would seriously consider the pointing. Next I would inspect the flashing between chimney stack and roof; water will take easiest route and although the damp patches are in the middle of the wall it could just mean that there is a section of poor pointing in that area allowing damp to seep through.

I would certainly cap the chimney; not to entirely seal it but to cover sufficiently to exclude the climate but leave ventilation which is a must; I've been trying to find pictures of our chimney problems; I ended up rebuilding the entire chimney stack from roof upwards and as our chimney stack was open at the top I installed a new two piece chimney pot; this pot is sealed at the top but with lots of ventilation slots on its face; our chimney is lined.

I can understand you being worried because it's the kind of job that really does need sorting out with some urgency; it could pay you to get a reputable building inspector in to save you lots of messing around if you are not used to doing building work yourself and also safety comes into this; a fall from a roof can and will kill even from normal house height? Ours is a bungalow but I take safety very seriously indeed. If I can find the pictures later I'll be happy to post them.

This might sound silly but think of yourself as a drop of water and you want to get into a house; start at the top and work down; water can also come from below and even leaking pipes? Don't just glance but really inspect using your eyes and take nothing for granted.

If the chimney is to be pointed then please use correct mortar mix; too strong a mix will cause more damage.

I was about to head into the workshop when a thought occurred to me; why did your house need to have new damp proofing added; water can also climb as well as fall? Is there landfill against the outer wall? This is a difficult one to answer with limited information but once the source of the water is found it will suddenly be so obvious? Have you inspected under the floorboards to see if there is water present. If the source of the water isn't found it's not going to go away on its own.

Good luck.

Kind regards, Colin.

 

[Retired]

Hi,

Below are pictures of the new chimney stack and two piece chimney pot I installed. This started out as a repointing job after water ingress to the ceiling directly above our front room fireplace; as I hit the chisel with the hammer the whole chimney stack wobbled; it being Easter holidays I was unable to buy the correct random stone but bought these from a builders merchant.

If your chimney is OK then work downhill to the foundations looking for where water could enter.

Kind regards, Colin.

The new stack completed with the bottom of the new chimney pot bedded in a concrete mix.

The completed chimney; the upper section is well ventilated around its face but the top is completely sealed; it's quite a few years since I built the new chimney and no problems since. I installed the new roof with lead chimney flashing about 28 years ago.