600mm centres - Wood or plasterboard?

[Ben WW]

Hi all,

So now comes my first real predicament in the man cave/shed build.

I put roof timbers in at 600mm centres with no noggins.

I now have the predicament of the ceiling finish. I will be putting in a VCL and then covering but I can't decide plasterboard over timber.. final finish aside, which is less likely to bow under its own weight.

Looking into it if I go the PB route I should be using 15mm board.. unsure of the timber requirements.

Any ideas would be really helpful.

Ben

 

[^woody^]

12.5 PB is fine @ 600 centres. Screws not nails max 200mm spacing.

 

[Ben WW]

12.5 PB is fine @ 600 centres. Screws not nails max 200mm spacing.

Thanks Woody. I would look to tape and joint it so no extra plaster skim weight. I don't mind the extra few pounds a board.. is it worth the extra to go for 15s?

 

[^woody^]

Weight wise, those joists/rafters look close to being over-spanned as it is, and if so, adding more weight than necessary should be avoided.

Are they suitable for the span?

Also, the purpose of noggins is to stiffen the whole roof up and make it "load sharing". So without noggins, each joist/rafter can potentially deflect individually, and increase the risk of cracking.

 

[Ben WW]

Weight wise, those joists/rafters look close to being over-spanned as it is, and if so, adding more weight than necessary should be avoided.

Are they suitable for the span?

Also, the purpose of noggins is to stiffen the whole roof up and make it "load sharing". So without noggins, each joist/rafter can potentially deflect individually, and increase the risk of cracking.

Hi Woody. Very perceptive. They are slightly overspanned i think. Hence why I want the lightest possible but so it won't sag under its own weight.

I wouldn't mind fitting some form of hollow board etc to keep the weight down.

Wasn't sure which would weigh less, timber or plasterboard but like I say, happy to try alternative materials too.

 

[mikeey84]

Would magnesium oxide board work? That can be got pretty thin, but not sure if it can be used for this application?

 

[^woody^]

15mm board will be what 25% or so more weight than 12.5?

If finish cracking is a potential issue then a more flexible ceiling such as timber may be better as it wont crack.
Or you could always paper it if plasterboard cracks.

But I do think omitting noggins is a mistake and increases the risk of individual joist deflection

 

[^woody^]

Would magnesium oxide board work? That can be got pretty thin, but not sure if it can be used for this application?

I think 600mm joists is too wide for MgO boards, but its the joints that will be the problem, no nice way to cover them.

 

[mikeey84]

I think 600mm joists is too wide for MgO boards, but its the joints that will be the problem, no nice way to cover them.

Are MgO boards a lot lighter than pboard?

 

[^woody^]

Are MgO boards a lot lighter than pboard?

My back says no, and thanks for reminding it of three years ago.

A few kgs heavier for same thickness, but normally you can use a thinner board for similar performance

 

[dontbelieveawordofit]

bit general imo , given theres no roof timber size or span mentioned.