Advice on stripping back to brick with damp walls

[giznorm]

Hello all.

First, thanks so much for any help on this, and all the excellent advice in the forums. What a great website!

I have just bought a house (yay) and it has damp (boo). According to the damp survey from before the house purchase, this is hygroscopic salt contamination of the plaster because of the use of gypsum-based plaster, and NOT rising damp.

Obviously one option is to strip the wall, treat it and replaster it with a non-gypsum based render. However, I was wondering if just stripping the plaster off and going to exposed brick wall would also be an option? I'm new to all this so would really appreciate any thoughts from those more in the know if exposing the brick would be a good idea in this instance, and potentially painting the brick with a breathable masonary paint.

Thanks again in advance!

 

[JP_]

Are the walls solid? If there is no insulation then it would be better to install some and create a vapour barrier at the same time.

 

[Mottie]

Depends where it is - inside/outside and whether it would look shyte if all exposed brick. The bricks/mortar could look quite bad if you damage them taking the plaster off. The only experience I have was when we bought our first house. We had to have the bottom 3 feet of plaster removed all round the inside of the house and after the damp course injections it had to be rendered with washed sharp sand (no salts) and then skimmed with a finish coat of plaster.

 

[giznorm]

Are the walls solid? If there is no insulation then it would be better to install some and create a vapour barrier at the same time.

That's a very good question jonbey, and information I should have included in my original post.

Yes, the walls are solid. It's a 1930s semi.
Interestingly, all the walls with damp are internal walls in the centre of the house and it's these internal walls I'm considering taking back to brick.

 

[Mottie]

I'd imagine a 1930's house might have some nice cornicing fitted. If so, how would that look against bare brick?

 

[giznorm]

I'd imagine a 1930's house might have some nice cornicing fitted. If so, how would that look against bare brick?

I imagined that too. Previous owners have removed all original features ... which I guess is why I'm thinking a little dramatic in terms of getting some character in there. The lack of features and the damp in the plaster made me think exposed brick might be hitting two birds with one stone.

 

[JohnD]

the internal brickwork might be horrible. As it was intended to be concealed under plaster, you may find reject, deformed and broken bricks and blocks used, gappy mortar, no pointing, uneven beds. Skilled (expensive) bricklayers, and good materials, were only used where they show.

Are you sure there isn't a water leak under the house? Old pipes usually leak. Is there a water meter?

Was the damp survey carried out by someone who sells damp-proofing treatments?

 

[JP_]

I'm a 1930's home owner too - 1934 bungalow, 2 years and 1 month in, still renovating!

I'd get the external walls insulated first, then repair damaged internal walls - once you've found the for source of damp.
I would guess that if the walls were damp then a good chance damp will be in the floor too?

 

[foxhole]

Is damp on chimney brest or adjacent walls?

 

[giznorm]

Is damp on chimney brest or adjacent walls?

There is a little damp on chimney breast but that has been improving with a newly installed vent.

The main bits of damp are actually in the centre of the house away from the chimney breast.

 

[foxhole]

Damp surveys are notoriously unreliable, how was it established you have damp walls? Who did the survey.

 

[giznorm]

Damp surveys are notoriously unreliable, how was it established you have damp walls?

Initially it was established because the evidence is visible (salt lines, discolouration). It was then picked up in homebuyer's survey and then we paid for a specific non-invasive damp survey. I wasn't present for the survey, but they put it down to hygroscopic salt contamination in the report.

 

[foxhole]

Non invasive means they did not drill the wall and take a sample, which is the only way to establish damp.

 

[bobasd]

OP,
there's a number of questions ref what you and others say.

1.when dealing with Your damp problem there's no need to insulate the walls.
2. can you post photos of the damp signs on interior walls, and on & around the chimney breast?
3. rising damp moisture contains chemicals that display on the decorated surface as hygroscopic salts - they bring moisture and they attract moisture.
4. 1930's unswept chimney flues contain soot, and that soot will become chemical and show on the finished surface of the chimney breast.
5. flues need to be swept and ventilated bottom and top.
6. analysis of mortar beds will show any rising damp chemicals.
7. DPC courses internal or external can be bridged by plastering/rendering over or by ground levels.
8. do you have good through ventilation below the floor - how many air bricks front and rear?

 

[foxhole]

OP,
there's a number of questions ref what you and others say.

1.when dealing with Your damp problem there's no need to insulate the walls.
2. can you post photos of the damp signs on interior walls, and on & around the chimney breast?
3. rising damp moisture contains chemicals that display on the decorated surface as hygroscopic salts - they bring moisture and they attract moisture.
4. 1930's unswept chimney flues contain soot, and that soot will become chemical and show on the finished surface of the chimney breast.
5. flues need to be swept and ventilated bottom and top.
6. analysis of mortar beds will show any rising damp chemicals.
7. DPC courses internal or external can be bridged by plastering/rendering over or by ground levels.
8. do you have good through ventilation below the floor - how many air bricks front and rear?

He doesn’t have rising damp, no one does.