Single Skin Porch - Insulation issue or just paranoid?

[MrC74]

Hello, I've recently had a single skin porch built. It's apx 2 meters square. A very simple/basic construction with a pitched/tiled roof. We have 1 x 900mm window (vented) on each side and a normal size front door. The builder was great, no problems.

To be clear, we had to go with a single skin brick as we did not have room for a normal cavity wall on each side (existing doorways/windows did not allow the room). Also, we wanted to maximise internal space for the new porch.

So, internally, we have a CLS timber frame which is battoned to the brick wall. In between the CLS frame, we have 50mm Celotex (foil on both sides type).

I'm just starting to finish the inside with pine timber cladding (apx 10mm thick) running floor to ceiling. I've completed one side as we wanted to get a Radiator fitted to keep the porch warm.

As I've started to move around the porch, I'm checking behind the celotex as I noticed in a couple of areas the brickwork behind felt a little damp to the touch. Now I'm not sure if this is normal for single skin walls or just additional moisture being created as I'm working in the porch.

I should point out here, the inside brickwork was painted with Bichomen paint. The builder suggested this and said this would stop any damp coming through from the outside.
I understand this, but I'm now slightly worried that we've created a barrier where moisture cant get out as such!

So I'm in a bit of a catch 22. Obviously the last thing I want to do is go back to scratch, but I dont want to ignore a potential problem either. I wouldn't say the moisture on the wall is "dripping wet", if anything it sort of feels cold to touch and a little moist.

I just wanted to seek some views on whether this does indeed sound like a problem I should try and rectify now or if it is me just being a little paranoid and to carry on with my cladding and hopefully once fully clad all round and sealed when painted etc, no moisture will be able to get through to the brickwork....or is that just wishful thinking?

 

[noseall]

Brickwork will get wet when it rains - obviously. But, it does not always reach saturation point. Rather it gets wet and it dries again. Prolonged driven rain does have a chance of creating water droplets on the inner surface unless steps are taken - which you have done with the bitumen. Robustly I hope.

Another thing to consider is the migration of internal moisture onto the brick surface and condensation. A robust VP (vapour barrier) and decent thickness of insulation are enough to counter this.

 

[motorbiking]

Any particular reason for the CLS? You could have used PL4050 or PL4060 celotex, frame fixated directly to the block and avoided the timber work, plus the insulation result would have been better.