Insulating a small cupboard wall.

Rorschach · Post by **Rorschach** » Thu Jan 30, 2025 7:41 pm

We have a cupboard internal to the flat but one small wall is an external wall. This wall is normally 5c colder than the other walls in the cupboard and as such in the winter it will often get wet with condensation and even though I use anti-mould paint it will usually go black after a while (as well as getting items next to it wet).

I am thinking the best course of action is to insulate it with some kind of board and then put plasterboard over it. Wanting some advice on the best way to go about this with budget in mind.

I was thinking something like this and then plasterboard over it. Is 25mm enough? The wall is small enough I could probably double it up to 50mm just from one pack.

https://www.diy.com/departments/jablite ... 830_BQ.prd

The wall won't have anything attached to it so could I use foam to fix the insulation and the plasterboard?

Grendel · Post by **Grendel** » Thu Jan 30, 2025 8:18 pm

That would work. You might even get lucky and find some kingspan off cuts in a skip that would do the job. 25mm is plenty , probably 12mm would be sufficient. Personally I'd cut it tightly and not worry about gluing it to the wall , perhaps just caulke around the edge and I probably wouldn't bother with the plasterboard but that's up to you. I did have a similar problem in my old house. Cold wall that moisture condensed on leading to mould on a couple of my wife's clothes. In that case I used a wooden frame with a slatted face which gave me an air gap and kept the clothes away from the wall. Seemed to solve the problem.

Rorschach · Post by **Rorschach** » Thu Jan 30, 2025 8:26 pm

I've got Kingspan offcuts, but nothing anywhere near big enough. Wall area to cover is approx 2m square so probably not going to find offcuts that big and I don't have a big vehicle now for transport.

I will need to glue it because the ceiling slopes but good to know foam will work ok.

I will likely put a sheet of 9mm plasterboard over it just to give a nice surface I can paint and keep it nice and bright in there. While I am not concerned about it looking perfect as it is only a storage cupboard, I do go in there multiple times a day so I want it to look somewhat tidy.

dewaltdisney · Post by **dewaltdisney** » Thu Jan 30, 2025 10:10 pm

Quite frankly R, I would think Jablite polystyrene sheet would do it, BnQ £13. https://www.diy.com/departments/jablite ... lsrc=3p.ds Take a saw and cut it to size to get it in your car. Batten out, fill with Jablite and cover with 12mm plasterboard.

DWD

Rorschach · Post by **Rorschach** » Fri Jan 31, 2025 9:34 am

dewaltdisney wrote: ↑Thu Jan 30, 2025 10:10 pm Quite frankly R, I would think Jablite polystyrene sheet would do it, BnQ £13. <a href="https://www.diy.com/departments/jablite ... lsrc=3p.ds" class="skimlinks-unlinked" data-skimwords-word="https%3A%2F%2Fwww.diy.com%2Fdepartments%2Fjablite-polystyrene-25mm-insulation-board-l-2-4m-w-1-2m%2F26822_BQ.prd%3FstoreId%3D%26%26%26%26%26msclkid%3Dad03fe8b808312ac266099107899db69%26utm_source%3Dbing%26utm_medium%3Dcpc%26utm_campaign%3DMerkle_Standard%2520Shopping_All_Building_Building%2520Part%25202%2520%28Bing%29%26utm_term%3D2329177945373476%26utm_content%3D1.%2520BO%2520-%2520Building%25202%2520-%2520Building%2520Part%25202%26gclid%3Dad03fe8b808312ac266099107899db69%26gclsrc%3D3p.ds" data-skim-creative="500005" title="" style="">https://www.diy.com/departments/jablite ... c=3p.ds</a> Take a saw and cut it to size to get it in your car. Batten out, fill with Jablite and cover with 12mm plasterboard.

DWD

Do I need to worry about battening? Was planning on just using the foam adhesive.

dewaltdisney · Post by **dewaltdisney** » Fri Jan 31, 2025 9:51 am

I was thinking of a frame to take the plasterboard, just a simple frame around the edges made of say roof battens with a Jablite filler.

DWD

Rorschach · Post by **Rorschach** » Fri Jan 31, 2025 10:13 am

I was just going to use the foam to put the plasterboard onto the insulation, possibly with a few screws going through into the wall behind just to keep it steady. As I said in the OP there will never be anything attached to the plasterboard other than a few coats of paint.

dewaltdisney · Post by **dewaltdisney** » Fri Jan 31, 2025 10:56 am

Gluing it all will do it, I probably over-engineer everything

DWD

Rorschach · Post by **Rorschach** » Fri Jan 31, 2025 12:15 pm

I am usually the same but in this case I am doing my best to keep it simple and easy.

Grendel · Post by **Grendel** » Fri Jan 31, 2025 5:05 pm

I've glued kingspan in place with panel adhesive without problem. If you have offcuts would there be enough to cover it all in pieces and then tape the joints? All you'd really need to buy then is the plasterboard.

Rorschach · Post by **Rorschach** » Tue Feb 04, 2025 8:06 am

Grendel wrote: ↑Fri Jan 31, 2025 5:05 pm I've glued kingspan in place with panel adhesive without problem. If you have offcuts would there be enough to cover it all in pieces and then tape the joints? All you'd really need to buy then is the plasterboard.

If I can get enough offcuts I'll do that, I won't be tackling the job until we have some warmer weather anyway. Otherwise a sheet of poly from B&Q is only £12.