Wet Bricks

[safcaph]

Hi

At the rear of my house (single story bathroom extension), the exterior bricks are soaking wet, in a kind of horizontal, metre wide / long patch, about halfway up the wall (1.5 metres up, wall about 3 m high).

Any ideas of (a) what will be causing this (water from inside - the bath / shower is on this wall), poor drainage from above (there is none!)?

and (b) what course of action is needed to remedy.

I'm fairly sure that wall has no damp proofing. I am wanting to renovate that bathroom so want to get everything in order - the room itself is cold and damp (tiles on this exterior wall are always wet unless I use my dehumidifier)

 

[LazyMark]

If the room is cold and damp and the tiles are wet it is probably condensation, however it is difficult to diagnose from this description. Any photos?

 

[safcaph]

If the room is cold and damp and the tiles are wet it is probably condensation, however it is difficult to diagnose from this description. Any photos?

Cheers for the reply - yeah I'm sure the internal issue is condensation cos when I use my dehumidifier (or window open in summer) it is fine. Its more the external bricks that are concerning me - why are they wet in a band, half way from floor to top?!

 

[PerryOne]

Are you writing about a 9 inch solid wall, or a cavity wall?

Humidity is a strange thing!
We are describing a very fine gas, that can and does find its way into nearly everything.
Bricks and walls cannot be described as damp proof.
Merely in some instances damp resistant.
Walls are not built as waterproof, merely as a way of shedding excess water.

So what we have possibly, is a cold wall, that from time to time warms up on its inner surface, when you run a bath.

Now keep in mind that the wall is porous and cold and heat always moves to cold.
And water vapour always moves from warm to cold, then you have a situation where the damp from the bathroom humidity soaks into the wall and then migrates through the wall to the colder outside edge of the wall, where on cold dry days it migrates again into the passing air.
(Water vapour hates a dry patch of air and moves to fill it!)

What you need to do is insulate the inner wall with something like polystyrene, covered by a plastic vapour resistant membrane, covered by plasterboard, plastered, and finished in whatever you care for.