Rendered brick wall on timber frame cottage condensing on interior

[Dpirie76]

Hello all, we have a small thatched cottage (2 up, 2 down huge central double sided chimney breast in the middle) which is made up of timber frame, wattle and daub on a 3 of the 4 aspects.
The final aspect being, from what I can tell, single skin brick with what I assume is concrete render on the exterior (common for houses in our area to have the wall facing that direction in brick as it faces toward an airbase that was heavily bombed in the war, people have said many houses lost that end in raids and were rebuilt in brick).

The problem we have is condensation.
Partly due to the ancient sealed up timber windows (which I will be addressing this summer, the house is listed so have to replace like for like, no way of installing trickle vents), but I'm wondering the wall should be..

Insulated somehow? (celotex backed plasterboard inside?)
Lime rendered outside?

If anyone has any thoughts / experience, I'd love to hear it.

 

Thanks in advance,
Dan

[Simplysimon]

single skin brick hard plastered on inner face or lath and plaster?

[Dpirie76]

Thanks for the reply

From memory (working away at the moment) its lath and plaster, I haven't investigated fully yet, but it has blown away from a electrical conduit and it is not render (as I know it) or plaster.

[Ed Davies]

48 minutes ago, Dpirie76 said:

The problem we have is condensation.

 

That's on the inside of the brick wall?

[Dpirie76]

Hi, Ed, yeah, on the inside of the house.  I'm working away at the moment so can't post any recent pics, but is very damp and blowing what looks like lathe plaster, though I've not investigated fully to determine inner wall construction.
Incidentally, this room is right next to our badly ventilated kitchen, so lots of moisture form cooking, especially in this winter.

[mm289]

If a) the brick wall is built with portland cement and b) the render is cement then you will have no way for the wall to rid itself of moisture so it will be saturated and hence blowing the plaster. This though will have been the case for a long time so not sure why you would only see it now.... has anything changed recently?

 

Always worth doing the normal checks of blocked gutters, soil build up around base of wall etc. IME insulation will not solve the problem as the wall still will be wet. Even if you sealed it from the vapour generated inside the house the moisture rising from the ground (unless they put a DPC in when rebuilding wall) and water ingress through likely cracks in concrete render will keep it nice and wet. Also your timber windows will move with heat/moisture and the concrete render won't so it maybe that you are getting water ingress around windows as well.

 

Suggested fix would be get rid of cement render and re-render in lime. CO shouldn't object as visually it will be the same but more authentic and preserves the building.

 

Only challenges with this might be if the brickwall is built in cement then it gets a bit more problematic....... or if the bricks are soft they may get badly damaged by taking of the concrete render.

 

So, check how the wall is constructed, look for any external water ingress points and report back on any recent changes in circumstances for further ideas ?

 

Cheers,

 

MM

[Ed Davies]

10 hours ago, mm289 said:

This though will have been the case for a long time so not sure why you would only see it now.... has anything changed recently?

 

From the OP's introduction thread they've been in 2 years so change to heating or something could well be the trigger for the change.

 

How about getting rid of the cement render then putting on EWI (external wall insulation) then a more breathable render over that? I.e., if replacing cement render with lime render is practicable then putting in some EWI in between is not that much of an extra step. With thatch I'd think that the extra thickness at the top wouldn't be much of a problem, moving the windows out might be a bit more tricky.

[Dpirie76]

Hi, guys, thanks for the advice.
The wall is a gable end so no gutters, just the end of the thatch.  From what you have both said I think the prudent idea will be to investigate further from the inside to see what's occurring.
Long term plan (4-5yrs.......££s.... you know) is to re-thatch and in doing so re-render that wall entirely. In the meantime we're looking for a 'stop gap' solution that's best for us and the building.
Thanks again, hold fire on the replies for now, I'll get home this weekend and post some pics.  So you can laugh at my ridiculous predicament.

 

Edited February 5, 2020 by Dpirie76

[Ferdinand]

In a similar situation - half brick gable wall on 1850s cottage - I dry lined traditionally on the inside using wooden frame plus celotex plus a dampproof membrane then plasterboard, leaving a continuous cavity against the brick, then ventilated the cavity to outside using high and low airbricks.

 

Don't skimp on the celotex in that strategy.

 

Has been OK for a few years now.

 

Suggest you also properly ventilate the inside.

 

F

Edited February 5, 2020 by Ferdinand

[Temp]

Measure temperature of inside face of wall. Single brick wall probably cold enough for condensation.