Insulated plaster board ceiling - preventing cracks

17 Nov 2008
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United Kingdom
I am building an extension which has a number of rooms with a pitched ceiling. I am using Celotex insulated plaster board and would appreciate some advice on how I should best prepare the gaps/joints between the boards to prevent cracking. In other rooms, I filled the gaps with caulk etc and the plasterer applied mesh but I still have some cracks.
I am screwing the boards in place this time (approx 6" spacing) rather than using nails as I did before as I have had a few places where the plaster has popped around the nail head although I think this is more to do with movement of the timber rather than the nail failing and I suspect that even if I had used screws, the results would have been the same.
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Dont board any ceiling or soffit unless the backing is firmly fixed.
Screw up a couple of lines of noggins if you think it would help to firm it up.
Test the joists from above (if possible) for bounce or sway.
Make certain that the joist edges are level across the room.
Make certain boards land centred on joists.
The joists must be dry or they will shrink, and nail pop will result.

Why dont you allow your plasterer to determine how to fix the boards?
Thanks for the reply Ree.
The rafters (3" x 8") are firm and there is no visible movement in them and I am cutting the boards so that the edges are in the middle of a rafter. When I mentioned previously movement in the wood being the possible cause of the plaster "popping" where the nail heads were, I meant shrinkage. Having said that, the roof was on for quite a while before I put the plaster board up so everything should have stabilised I would have thought - it is not a major issue as only a small number of holes have appeared which I can easily repair!
My Dad used to be a plasterer and in his day (1940-1960) he used nails so Idid the same but the two plasterers I have used both use screws which I guess is the modern alternative! This is a self build project so I am doing as much as I can myself in preparation for the plasterers
My question really is that in the corners of the pitched roof, where I cut the boards which are at an angle, I inevitably have some gaps (1/4" max) between boards and I wonder if I needed to "plug" these gaps with anything other than caulk.
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Dont caulk anything - just allow the plasterer to do whats necessary.

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