I have get a big window replaced. The old window goes up to the slope of the roof, but now I want to close the corner part and was thinking about using wood framing with plasterboard on the inside. The plasterboard should be flush with the remaining AAC (Autoclaved Aerated Concrete) wall. Due to the two different materials I'm not sure if this approach would be prone to cracking.

Is it a good idea to combine AAC and plasterboard like this?

  • I added a Wiki link to AAC for those, like me, who weren't familiar with it.
    – FreeMan
    Sep 24 at 12:48
  • Is it just an expanse of yard and street outside this wall, or is there another building nearby? Sep 24 at 22:57

From this Wikipedia page, I quote:

AAC products may be used for both interior and exterior construction, and may be painted or coated with a stucco or plaster compound
Emphasis added

That would lead me to believe that the thermal expansion properties of AAC and plaster are similar enough that there wouldn't be any cause for concern about the coating flaking off due to cracking. Since a skim coat of plaster wouldn't be likely to crack off, I would assume that plasterboard/drywall would have similar enough properties to not be of concern.

Disclaimer: This is pure conjecture, but seems reasonable. I have no experience, professional or otherwise, to support this.

I would say, though, from further reading of that page, that it seems that AAC units are quite easy to work with, since they can be worked with standard woodworking tools, so you might want to consider filling in the voids with new AAC blocks instead. That would completely eliminate any concerns about dissimilar materials causing cracks.

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