Line of yellow discoloured paint appearing on original wall/new loft wall boundary.

GermanderSpeedwell

Thanks all for your replies.

The inner wall is not insulated, no. 

Based on what you are saying, is this a significant issue and do you think I should consult with another expert to investigate this further? If so, would that be another loft contractor, or a damp surveyor, or someone else? And should I conclude that what the original contractor has suggested (painting over the exterior area again once the walls have dried out) is enough to resolve this?

I suppose let them paint and then 'wait and see' is another potential option

GermanderSpeedwell

One other thing to bear in mind is that this loft extension was completed last May (2022), and so the wall had all summer to dry out following initial construction. The wall discolouration started appearing in early January this year.

ThisIsWeird

GS, this cannot be normal, and just cannot be a case of the wall needing to dry out further - I can't see any way of that.

And you reckon there is no internal insulation on that new gable wall, which is a 'solid' wall? I presume 'solid' means there's no cavity. So, where is the insulation? Because a wall built to current standards would surely have a good few inches of stuff there. Could it be a solid Thermalite block wall?! In which case being waterproof ain't one of its qualities.

I obviously haven't a clue, but - if that gable is a new build - then it surely should be very well insulated?

GS, why does that upper end gable wall look so tatty? That was given two coats of exterior paint last year?! Is it as blotchy in reality as it looks in the photo?

What I may suggest is that you call up the BCO who oversaw the job, and ask them to call in when passing - most will be happy to do this. See what they think. Ask about insulation...

The builder's suggestion of this wall being still wet, or it being fixed with the addition of further paint, are both very worrying in my view. I'm not a builder, but that doesn't sound at all right.

GermanderSpeedwell

Thanks for your reply TiW.

So, there is definitely internal insulation in the habitable rooms, where they put in timber studs and thick insulation in between. But in the 'landing' area above and around the stairs where we have the damp problem, I'm really not sure if there was insulation added. There may be a thin layer, but as the internal wall directly matches the width of the existing wall below, I'm not sure there could be anything significant. Below are some photos during the construction of the wall that may give some clues on the construction as I'm really not sure:





In terms of the paint - below I'll put a photo of the painting just after it was done, and another photo taken recently. It does look like the colour has changed somewhat (some tattiness/discolouration as you noted).





Thanks for your suggestion for going back to building control. I will do that and I will see what they say.

ThisIsWeird

That's a 'solid' wall all right!

Concrete blocks are around 8.5" thick, so when rendered outside and plastered internally, that'll be more like 10"? (folk will confirm). Can you access that gable window, and check the thickness betwixt inside and out - see how it compares?

I don't understand what went on there, if there really is no insulation. There are surely alternatives that could have provided a full level of insulation, and it being the stairwell is no excuse - that is almost certainly going to be the coldest wall in your whole house, so will be the first surface for any household condensation to form on. I wonder if that could even be what you are seeing - staining from internally-formed damp? But that is mere pondering on my part.

We had a loft conversion done nearly 20 years ago, with a hipped end made into a gable. This new gable was a fully timber construction, lined both sides with 18mm (or 22mm) ext plywood so was immensely strong and rigid, and the inside voids fully filled with insulation. Outside was Tyvek'd, meshed and rendered - still looks pristine, and repainted only once during that time.

DRP

The insulation will be between those internal studs won’t it?

ThisIsWeird

DRP said:

The insulation will be between those internal studs won’t it?

D'oh - missed that in the photo. Presumably the studwork shown goes along the whole gable? Blimey, that's a thick wall.

What's going on with that wall, then? How on earth does a potential seep along that render joint show up beyond what looks like a 4" stud?

Doozergirl

I definitely don't like the join between the two areas of render.   That isn't good enough, imo as it looks like water can actually sit on the little edge of it and seep through.  

Has the question of the internal being currently or ever wet been answered yet?  

stuart45

ThisIsWeird said:

DRP said:

The insulation will be between those internal studs won’t it?

D'oh - missed that in the photo. Presumably the studwork shown goes along the whole gable? Blimey, that's a thick wall.

What's going on with that wall, then? How on earth does a potential seep along that render joint show up beyond what looks like a 4" stud?

The stain is in the stairwell, where the thickness of the wall has to match below.

GermanderSpeedwell

@ThisIsWeird to answer your question, there is 13 cm to the window frame, then the window frame is 6cm, then I guess there is 5cm or so after that (I can't open this window) giving a wall of around 24-25cm.

You're right that there is a board or something on the internal wall giving a 'hollow' sound when you tap it, compared to the solid brick on the lower floors. I don't know how much insulation they managed to fit between the blocks and the board.

@Doozergirl , I have never noticed or felt that the wall has been wet to the touch, if that's what you mean. I have only noticed the discolouration until now. Could the join between the render between the two areas (exterior wall between old brick wall and new loft blockwork wall) have been done in a different way to avoid this issue? Is this something I could mention to our loft contractor, or should I get someone to investigate further first?

Thanks again all,

GS