Weird plaster issue at 400mm centres

[Adsibob]

Moved in about 10 days ago. Was putting in one of the final light fittings in my loft conversion this evening, and noticed that the plaster/paintwork had cracked in a very regular pattern at the ceiling, just by the join with the wall. I haven’t got a ladder to measure, but it definitely looks like the broken patch is exactly every 400mm which I presume matches the spacing of the timbers supporting the roof. Most of the patches are about 3.5cm in diameter, but one is almost 6cm in diameter. It’s very weird. I attach some photos. Anybody think I should be worried about this, or is it normal settlement? I only noticed it today, and I couldn’t say when in the last couple of months it happened. This was finished plastered at around January, and painted around mid March, so I guess it could have happened in the last couple of months. Only other possible cause is we had our MVHR commissioned 6 days ago, so maybe it has dried out the walls and ceiling? But we haven’t had this issue anywhere else.

 

 

Edited May 19, 2022 by Adsibob

[Adsibob]

Another photo

[PeterW]

Nail pops - has the board been hit..?

[ProDave]

Yes nail or screw heads popped.  That usually happens if the screws were not tight so the board was not pulled tight to the timber, then it can move and pop the plaster off the screw heads.

 

If there are only a few, remove the loose plaster, tighten the screw and skim over it again.

[Adsibob]

Okay, well that is somewhat reassuring that it is not weather related. It doesn't seem to have happened anywhere else in the loft conversion, although we have cornicing that would probably cover it up in the room next door. But what would have caused the board to move?

[SteamyTea]

Is it plasterboard with insulation attached to it.

Nearly every place I have seen that used, seen the screw heads pop.

[Adsibob]

20 minutes ago, SteamyTea said:

Is it plasterboard with insulation attached to it.

Nearly every place I have seen that used, seen the screw heads pop.

Yep, Kingspan Kooltherm K118 insulated Plasterboard! Why does it cause that?

[SteamyTea]

13 minutes ago, Adsibob said:

does it cause that

In my limited experience, yes.

Trouble is, it can move too much.

[Radian]

I often wonder if pops might happen because of drying-out. Our houses internal timbers went through a very wet winter with no roof. The pops only started appearing some months after we moved in. If the surface of the timbers shrank back towards the centre then plasterboard fixings (nails in our case) might be anchored in dry wood while a small gap opens up between PB and timber as the surface layers of the wood dries out. The chipboard flooring was even worse as it started creaking and groaning against the nails (ring shanked, no glue). Ah the good old days before expanding glue products. Further evidence might be that the floor got so creaky that the builders came back, lifted all the upstairs carpets and threw hundreds of screws in. It fixed it perfectly - for a year or so. Since then it's gone back to walking on a comedy floor.

[Faz]

It is the MVHR regulating humidity.  I had the same - moved in 17th Feb. Heating just gone on and didn't have much time to slowly ramp it up and MVHR commissioned pretty much at the same time.  What would take a 'normal' house to dry out happened at least 10x faster.  

 

Only had 1 board pop with a couple of drywall screws so that isn't much of an issue.  The cills and architrave and the like shrunk real quick.  I stocked up on some caulk and will probably hit it late summer if I can be arsed.

 

So maybe in a year to 2 then.....

[WWilts]

On 20/05/2022 at 18:46, Faz said:

cills and architrave and the like shrunk real quick

Is it advisable to paint the cills/wooden window boards before skimming the plasterboard walls/ceiling? As a way of reducing expansion & shrinkage of the window boards?

[Faz]

They normally come pre-primed so it won't make much difference.  If you are doing it all in summer then this will help you.

 

At the end of the day the timber is going to shrink - just leave it for a year and then sort it all out with caulk when it has stabilised.

[Haylingbilly]

I have the same problem, with the second fix being done in last December (2021). When do you think I should fill the gaps and fix the popped screws - this autumn, next spring or next Autumn - I only want to do it once!

[Faz]

I only have one screw that popped and I am going to patch it up fairly soon as a temporary fix.  Will go for the cills and any other cracks when I can be arsed next spring.