Chimney Breast Removed, Now Mouldy Skirting

[simojo]

Hearths are damp because they are in contact with the ground and damp rubble. Yours still is.

Tape a piece of clear plastic tightly to it, see if water droplers form underneath.

What is your hearth now covered with?

The hearth area now has laminate with 3 mm foil back underlay over it. I am hoping not to have to take too much of the floor up but sounds like to sort it once and for all I may need to?

 

[JohnD]

I think so

Firstly you will hopefully be able to see the size and severity of the damp

Secondly you will be able to do something about it.

I think with a very fine saw you will be able to take out a rectangular section. Make it plenty big enough to avoid having to cut it again.

Once it is uncovered, water will start evaporating off the surface. If it evaporates faster than it is absorbed from the ground, it will get drier. But it get wet again if you cover it.

 

[mrrusty]

Stop! don't start cutting your floor up. It was a chimney in a 1930's house. For sure there will have been combustion products, water sometimes coming down the chimney and lime and other building products in the bricks and mortar. The bricks backing the chimney will be loaded with salts created by the reactions of combustion products with water/ lime etc. - just google "hygroscopic salts" and "chimneys" and read umpteen articles on the subject.

The problem is that the salts in the bricks attract moisture from the room air making the wall seem damp, and allowing crystals to grow - often can be seen as fluffy white efflorescence . Often , plaster and skim looks like it never dries. The problem is exacerbated when wet trades (plaster, dabs, self levelling etc.) are applied over salt contaminated bricks - the water in the "wet trade" draws salts from the underlying fabric as that water evaporates as the material dries, drawings salts to the surface, that then carry on pulling moisture out the air.

Dehumidifier will help, and also damp seal paints and primers can work to some extent (in my practical experience) to stop humid room air getting to the salts. A better fix is to strip back to brick, and isolate the salts in the brick from the plaster decoration (again in my practical experience - foam plasterboard adhesive proves to be a very efficient barrier to salt transmission). It is also quite possible that the hearth is still damp from all the water that has come down the chimney and as this moisture is evaporating, it is also being absorbed by salt contamination exacerbating it.

Personally, just 3 months in I would live with it for a year and see where you are. You can then take a view as to whether it is a big enough problem to intervene or not. It's an older house - it's always going to have a few areas that need attention occasionally

 

[blup]

The hearth area was chiselled out about 15 mm depth below the concrete floor before the self level put on top (probably not enough as was doing myself and didnt realise it may cause issues). That is my thinking with residual mositure from years of moisture getting down chimney. Think I need to take skirting off, treat any mould, maybe put some damp cream in some holes around the floor and then do my best to proper dry it out with heater and dehumidifier

In that case the damp is still rising from the ground, you need to remove it and apply appropriate damp proofing. Or at least chisel more out and paint with bitumen.

Blup

 

[JohnD]

Photos of the outside, including DPC, pipes and drains would still be useful.

 

[mrrusty]

laminate with 3 mm foil back underlay over it.

One thing we can be certain of - if there is any damp in the old hearth it isn't getting through foil backed underlay!

 

[^woody^]

One thing we can be certain of - if there is any damp in the old hearth it isn't getting through foil backed underlay!

It moves sideways.