What material to fill large gap in corner of cupboard?

[chainsaw_masochist]

I will shortly be having a new boiler installed in this cupboard. Before this, though, I would like to tidy up the considerable gap that runs pretty much from top to bottom - at the lower section you can see the exposed lathes. Would I be able to apply some expanding foam into this gap or is it better to use a bag of readymix? Obviously because the cupboard will house the boiler it does not have to be done to a particularly high standard but I would at least like to put a coat of paint over the finished surface.

Thanks for any advice.

 

[Doggit]

Have a look at Thistle one coat plaster (wickes about a tenner) as it'll fill to a depth of 2" in one go, and polish off to a reasonable plaster finish.

 

[lostinthelight]

If you use one coat plaster I would damp each side of the gap and possibly mesh it or it could pull away leaving you with a smaller crack. You could also pva it to reduce suction.
litl

 

[chainsaw_masochist]

Thanks very for the comments, guys. I'll try to get some one-coat plaster as I am not far from a Wickes. A mesh fixing sounds like a good idea. Would you completely disregard using expanding foam for this type of job, though? It has occurred to me that I could use the foam behind the mesh to reduce any draft etc. Accept that it might be totally inappropriate, though.

 

[Doggit]

As the one coat plaster should cover the holes, then the foam shouldn't be needed, and as long as you've got a stiffish mix, and you've PVA'd the sides so that it cuts down the suction, then you should be fine. You'd normally use the mesh across a crack, and then plaster over it, but unless you're then plastering around the corner, the mesh on that side wouldn't be secured.