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Plastering & Rendering

Noggins in flat roof joists - cracking plasterboard

Anonymous user 23/02/2024 - 3.28 PM

Hi We recently completed an extension which had a flat roof. 9" x 3" joists were used as spec'd by an engineer spanning a 5m width. Noggins were only installed at the absolute end of these joists. Soon after the roof was installed (joists, osb board, insulation, osb board, grp) - we had the ceiling and walls boarded then plastered (approx 5 days). We are now getting cracks in the plasterboard where the joints are. I have been told by my plasterer this is likely down to moisture in the wood drying out and expansion/contraction. Similarly - where we had steel beams installed across the span to support a roof lantern, fire board was used and this is cracking all along the joints too. I believe the plastered used an orange scrim tape (Gyproc) along all the joints. I am a little worried that this is more than the above - but would welcome some thoughts from other tradies! Thanks

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4 Answers

Anonymous user

This can happen I’ve heard similar stories in fact my plaster was telling me of a one like yours when he was plastering a ceiling for me this summer funny enough, and I’d agree with the plaster and say the timbers are drying out it’s incredibly unfortunate and unlucky but it’s a risk when having building work in the winter and timber getting damp and wet. Maybe more noggins would had help prevent this but it’s anybody guess really if I’d built the flat roof I would had put noggin in at every 500mm/1m apart myself but I do like to be extra but I just like to sleep easy so... I’d wait a little while let everything properly dry out which shouldn’t take too long as it’s winter and cold you can just put the heating up a little more then get the cracks repaired or just re skim which ever is easiest and cheapest option

Answered1 December 2019

Howes Building Services

Rating: 5 out of 5

Nottingham

its because of the wood drying out, so its moving, the colour of the scrim is of no consequence as its just easier to see where you have and have not put it.

Answered1 December 2019

Jason Wood

Rating: 5 out of 5

Manchester

Plaster only cracks if it can move or there is movement

Answered1 December 2019

I R Tiling and Plastering Services

Rating: 4.7 out of 5

Leeds

I would have put more noggs in every 400 to span out some times it can crack h as the boards been put up right and been stager

Answered6 December 2019