Which of these don't need skimming?

[MrsRenovator]

I can't find the answer from Google. I need to ask a real person please...

I'm short of space for covering retrofit internal insulation on window reveals that are attracting condensation. So I'm looking for something slimmer than PB and skim. I've read about 6mm MgO. Also Magnox. (Even after reading about it, still not even sure what that is!)
I don't want to use ply. And I want to be able to paint it.

What can you suggest that can be dry lined, primed and painted without being skimmed and as slim as possible? If any....

Thank you

 

[MrsRenovator]

Here's another thought... What if I used 3mm undercloaking board? Would that need skim on top to get a nice finish? Or in fact, can you skim over it??

 

[jacko555]

Sempatap

 

[MrsRenovator]

Thanks.

So now I've read about Sempatap. But the I value isn't low enough for what i need. I'm going to use Aerogel blanket on the reveals. But I still won't have space for PB and skim.

 

[endecotp]

What is the current construction of the reveals?

 

[MrsRenovator]

10mm plaster straight onto the top metal lintel. Sides are 12mm plaster.

 

[endecotp]

Are you proposing to remove that plaster?
How much additional thickness can you manage?

 

[MrsRenovator]

We're just hacking away at it now. Looks like maximum 20mm.
I've seen you can get Spacetherm with MgO which is 13mm. Very expensive, but no point me doing half a job. Online, delivery is over £35 though. Don't they stock it at local builders or anywhere?

 

[endecotp]

No, aerogel is not sold anywhere mainstream. No-one "sensible" buys it; it's totally uneconomic.
I have some that I got from an ebay seller in Italy; that's just the insulation, not bonded to anything. If you could get some thin MgO board it would not be difficult to assemble.

I think your best option would be 20mm Marmox multiboard:
http://www.marmox.co.uk/applications/plasteringrendering-the-insulation-board
I believe you can fix that to the brick with tile adhesive, and skim over it.
The insulation is only XPS, but it does make up the majority of the thickness.
(Hmm, the board itself is 20mm so it will be thicker once you've included skim and adhesive; if you really need a total thickness of no more than 20mm, unfortunately the next size down seems to be 12.5.)

 

[MrsRenovator]

No-one "sensible" buys it; it's totally uneconomic.

That's me then. Not sensible.

If you could get some thin MgO board it would not be difficult to assemble.

I've seen 6mm MgO board for sale, although again, not locally. But can't find 3mm anywhere. Is it the same thing as cement board? Or tile backer board? That can be painted I'd you use the smooth side out.

Why is everything so difficult to buy in small quantities. I don't want a pallet full. Is marmox the kind of thing that normal builders depots stock?

 

[MrsRenovator]

 

[MrsRenovator]

This isn't so much of a cold bridge, more like a cold express highway. I need super insulation in my sparce 10mm!

 

[endecotp]

Marmox, or other cement-faced insulated tile backer boards, are reasonably widely available.
I seem to recall buying a single board from an online source once.

Can you post a photo from further back? What is limiting the thickness of what you can fit there?

 

[MrsRenovator]

It's a narrow window frame. 52mm total. I didn't take any good photos. Will take some tomorrow.

 

[MrsRenovator]

I waited till the plaster was completely off before taking the photos to give a better view.