salt in wall causing damp patch

level200

hi guys

whilst re plastering my utility room i noticed a damp patch that was showing through the plaster board (external wall) after 4 weeks it remained and started leaving a salt like deposit.

Had a damp proof guy come round last night to have a look, he told me that it wasnt rising damp and it was just salt in the wall attracting moisture. I should cut out the damp plaster and re plaster with revovate plaster.

Does anyone know where i can get revovate plaster and also do i need to apply something to the salt to kill it off first??

Cheers
John

keystone

Don't agree with him - its moisture in the wall driving the salts out of the plaster (called efflorescence) - although it boils down to the same thing. You need to treat the cause ie dampness not the symptom ie the efflorescence.

He means renovate plaster not revovate.

Find the cause of the water first and deal with that. Once thats done and the wall is dried out then the salts will stop coming out of the plaster. You can either brush it off (don't wash it off 'cos you just add to the moisture and recommence the cycle), treat with anti-alkaline primer then decorate as normal or if you want you could strip back, use renovate plaster and start again.

Cheers

level200

Hi Keystone

Sorry i think revovate was a typo on my part.

We both had a look at the external wall and couldnt see any sign of damp or water damage, the damp proof course was ok. only thing that might cause problems was the flat roof but its a thick concrete slab, he suggested that when it next rains i should go out and have a look at weather the water is running off the slab roof onto the brick. if so add some guttering to divert the rain water away.

keystone

If its very localised have you considered the possibility of a leaking pipe in the wall?

Cheers

level200

No pipes in the wall at all

level200

Also mold and damp patch around the skirting board, again he said that it wasnt rising damp

level200

Sorry i'm at work and trying to remember what he said, he also suggested painting the lower part of the external wall with brick protecter

MRSTITTLEMOUSE

I've a little patch of wall in my kitchen(not an outside wall)that keeps attracting dampness.
Its in the middle of the wall,around 10 inches across and the little patch of wall itself does'nt get mouldy or anything just visibly water marked.
We even had a damp course done just incase but it still comes back.
Stain and damp paints don't work it still gets wet even though there is no pipe work and its an internal wall.
We've found running a dehumidifyer over night collects a lot of water and the wall is fine for a few days,perhaps its just condensation in that particular area as I take it thats what we get in the kitchen.

tony6403

Assuming that you have cavity walls , dampness can be caused by mortar deposits or rubble inside the cavity which allows moisture to pass between the two walls.
If all else fails you could carefully remove an outside brick in the middle of the damp area and check for any obstruction.
To do this neatly you would need a grinder or it can be done by repeated drilling of the joints.

iamcornholio

Being a utility room, the plaster could have absorbed some moisture, or there could be a natural cold spot leading to slight localised condensation, and this could have initially caused salts to deposit on the surface. The salts could well be hygroscopic (absorb moisture) and so become self-sustaining/perpetual

If there is no actual other source of moisture causing damp, then you don't really need renovating plaster