Plasterboard joins and openings

[princhester]

I'm plasterboarding a concrete block wall. It has a window in it. The way my sheets of plasterboard work out, it would be easiest to have a join in the plasterboard at the upper corners of the window. Boral's Usage Guide says this is a no no, and that joins should be more than 200mm from the corners of openings.

Does anyone know why? Perhaps if I understand this, I'll be able to work out whether I need to worry about this restriction in my particular application.

[HavinaGo]

Hi princhester,

My Jennings built place from the early 60's did not consider Boral's advice ... (maybe it predated the experience ... there are numerous cracks in the plaster that start at the window corners and follow the joins to the ceiling or floor along the joins. I put it down to the stress concentration caused by the sharp angle .. and the moving timber frame ... and the difficulty getting a good join all the way to the end of the sheet when the join is in a corner. None of the joins in the middle of a wall have given any problems.

Others will have to decide if the wall you have is less likely to move than the brick venier I have .. hence you might get away with it but plasterboard is relatively cheap and not too hard to work with and you have to look at it after.

[scooter]

Gday prin, I agree with Hav, the reason is potential movement in the frame of a timber (& presumably steel) framed house causes the plasterboard to crack up and down from the window corner at the join.

I have a '60s weatherboard house with cracks like this in a couple of the rooms, the house is generally well built otherwise but these are a pain. The place is on stumps which probably exacerbates any shifting caused by ground movement.

Per hav's last para, you need to assess whether the same sort of movement that a framed wall would be subject to will occur in your wall. I'd guess no, if it did you'd have bigger problems to worry about that plaster cracking I'd reckon :eek: . But I'm not a brickies / buiilder's arrrr....mpit (g'day )

ATTENTION PLEASE - PAGING AL OR MICK !


Good luck...........Sean the circumspect

[princhester]

I thought that might be it. I think I'll just do it: it's not in an area of the house that's exactly pristine anyway, so a crack isn't going to be the end of the world. The wall's been there for 30 or 40 years so I guess its done all the moving it's going to do. Maybe.

Thanks.

[journeyman Mick]

Prin,
A block wall shouldn't move, but mine has hairline cracks around the bottom of some of the window openings. Plasterboard is cheap as chips anyway and you'll kick yourself everytime you look at it if it does crack.

Mick the careful

[flat_tyre]

If you put a join near a window it will crack for sure...

[namtrak]

It has a window in it. The way my sheets of plasterboard work out, it would be easiest to have a join in the plasterboard at the upper corners of the window.

I'm not sure how the join could manage to be at the upper corners of the windows? Wall sheets are generally 1350 mm wide, which would mean you have a very low window?

Cheers

[bitingmidge]

Prin,
A block wall shouldn't move, but mine has hairline cracks around the bottom of some of the window openings. Plasterboard is cheap as chips anyway and you'll kick yourself everytime you look at it if it does crack.

Mick the careful

The wall itself shouldn't move, but the concrete blocks will continue to shrink for many years (even autoclaved ones). This isn't too disastrous in a properly constructed wall with the appropriate reinforcing, but explains why hairline cracks occasionally appear at the bottom of window openings. The tops are usually constrained by a structural ring beam or header.

The cracks should not be sufficiently large to crack plasterboard, but be aware that they are a weak spot for waterproofing and the board could get damp if the wall is an external one.

Cheers,

P (cautious user of blockwork)

[Mowy]

Hi princhester,

Are you plasterboarding directly onto masonary or are you putting up a frame first?

[princhester]

The wall itself shouldn't move, but the concrete blocks will continue to shrink for many years (even autoclaved ones).

They'd be 20 years old at a guess, certainly 10.

I'm not sure how the join could manage to be at the upper corners of the windows? Wall sheets are generally 1350 mm wide, which would mean you have a very low window?

End join, mate.

Are you plasterboarding directly onto masonary or are you putting up a frame first?

Wooden battens on a masonry wall. A very wonky masonry wall, hence the battens, to allow me enough of a margin to get things straight.