Is it a good idea to dry-line a north facing external wall?

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We live in a 1914 solid wall construction semi-detached house. My son's bedroom faces west on one side but the longest wall is North facing and external.

It's very hard to get the room warm enough in the winter, despite a decent radiator. The roof is pitched at that point and insulated as far as it can be (without redoing the whole roof). I'm wondering about installing internal insulation in the form of insulated plasterboards, but don't want to create problems with either condensation between the plasterboard and wall, nor anywhere else.

Any thoughts?

we've done it on a north-east facing external wall at least 200 years old. The insulated plasterboard has stopped the condensation and the room seems warmer.

quite a job to fit - heavy and needs lots of fill/smooth/tape/sand/fill etc etc.

Thanks specialsubject that's really helpful. Anyone else got experience of this - either DIY or trade?

I would , and use a breathable board like this thenaturalbuildingcentre.co.uk/product/homatherm-choosing-the-right-boards/
and then lime skim internally so you have a warmer wall but still breathes if there is any trapped damp

Thanks beaufontboy that's a very helpful link. Do you know if lime skimming is a specialist job or one that most builders who can plaster would know how to do?

The lime guy who came to ours, said - a lime specialist can plaster with any material but a normal plasterer cant do lime ! lime requires understanding of how to mix, and some local guys to me don't touch it for that reason, so yes specialist sorry, and slightly more expensive, your local conservation office should be able to help with some contacts.

I wouldn't agree with the breathing layer on the inside.

The room will be full of warm, moist air, which will travel into the wall and cause interstital condensation.

Instead, use a vapour barrier on the warm side of the insulation.

Tell us how deep the space is between the plaster ceiling and the tiles; and what is in there.

good point - we have indeed used board with a waterproof lining to prevent exactly the problem PJ describes. Remember that means no pictures on it.

beaufontboy, PigletJohn and specialsubject thank you for your replies.

PigletJohn I've got no idea how deep the space between ceiling and tiles is - need to go up and have a good look and measure which I can now do as we've boarded our loft - finally! (on top of insulation).

No pictures on the walls would not be a problem, as the plan is for bunk bed to go there which is part of the reason I'm thinking of dry-lining it so that it's not totally freezing for my son.

I will go and have a look and get back to this thread.

OK it's been a while but I'm hoping this will re-open the thread despite my delay in responding to PigletJohn's questions.

Above the room is the loft space and then the edge of the room where the window is, is a sharp pitched roof with very little space between the plaster and the roof tiles (I estimate 1ft or less with possibly a tiny amount of insulation or nothing there - it was too difficult to get to to see). In the other area, i.e. the main bit of the room, there is loft space above it which is insulated with rockwool type insulation between the rafters.

PigletJohn does that answer your question? What would you recommend based on this information?

If it is nearly a foot, then you can insulate it. If the ceiling is plasterboard, which is fairly smooth, you can cut mineral wool quilt (get the stuff with Ecose, google it) and poke it down the gap with a broomhandle.

If the ceiling is l&p, which is very irregular, quilt will not slide down but you can use rigid foam slabs like Celotex or Kingspan. Get the ones with an aluminium foil skin. You will have to cut them to fit.

Or, if the roof needs mending, or the ceiling replastering, include insulation in the scope of work. When you have access to the rafters it will be much easier.

You could also nail insulated plasterboard, which includes a layer of rigid insulating foam, to the ceiling, but it will be much thinner and not as good.

There is advantage in getting the roof retiled, because you can make it more weatherproof and add a breathable membrane to keep rain andsnow out.

PigletJohn wow you're fast! Thanks for all the tips. Not sure at the moment as my son is asleep in there and don't want to go in and wake him, but I think it's lime and plaster as I have noticed in the past that that particular bit of the ceiling looks bumpy / rustic.

Unfortunately, retiling the roof is not an option budget-wise at the moment, but it's definitely on the cards for when it is.

Is it still OK to insulate the West and North facing walls if we insulate the sloping bit if the roof in the way that you've suggested?