# Joist/Stud Spacing and metric/imperial lunacy.



## JoeS (16 Nov 2020)

I've always understood that studs for example are spaced at 400/600mm and that sheet materials are sized to correspond to these spacings. In reality whenever I've built a stud wall or any number of sheds, it's never ended up going totally to plan in terms of the spacing. 

What I don't understand is that the first cover of the sheet material is typically over a double distance (it should cover a whole stud - so lets say for ease 40mm), the sheet material "joins" in the middle of the span only covers half a stud (20mm) and the last should cover 50mm. I don't understand how even if a wall was built in totally perfect divisions of 2400mm (let's say my span is 7200mm) , how I would perfectly cover the last 40mm of stud or is my maths wrong?

My question is the same when thinking about laying down OSB onto joists on a new shed project. I suppose that's even more confusing because that is sized in imperial measurements!

I can't work in imperial and am a fully paid up mm man. Can anyone help me? I know this is a stupid beginner's question, but I've been googling around for a while and can't seem to find a very clear explanation. 

Please help!


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## Cabinetman (16 Nov 2020)

I’m not an expert, but I think it’s your lack of Imperial that’s causing you problems, a sheet of ply isn’t 1200 x 2400 it’s 1220 x 2440 which is 48“ x 96“ the old stud distance was 16 inches (which is approximately 400 mm) , three x16” is 48” so you can see how it all sort of fits. Ian


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## Spectric (16 Nov 2020)

Hi 

I dont like the sheets only covering 20mm on a stud so I add extra between nogins on one side and then each sheet covers 40mm and plenty of meat for the screws.


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## Jameshow (16 Nov 2020)

12" = 305mm

16" = 407

24" = 610

4' = 1220

8' = 2440

Cheers James


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## Doug B (16 Nov 2020)

JoeS said:


> My question is the same when thinking about laying down OSB onto joists on a new shed project. I suppose that's even more confusing because that is sized in imperial measurements!



You can get osb in both imperial & metric sheet sizes just depends on what you order


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## Doug71 (16 Nov 2020)

If imperial measure 48" from the outside of your first joist to the centre of your 4th joist and then it's just 16" centres for everything else. 

Tape measures normally have a little dot or diamond shape over all the numbers which are multiples of 16" and 400mm, depending if you are working with imperial or metric sheets just keep the relevant dots on the centre of the joist and you won't go far wrong.


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## JoeSheffer (16 Nov 2020)

I think actually what i might have been doing wrong is measuring centre to centre. I've just seen a chap on youtube measure from the end of the first joist/stuf and not the middle... so maybe this is what my error has been (i had been adding an extra half thickness to the calculation). Does this seem correct...so just run tape measure from edge of first stud/joist and mark the centres at 600/400mm (...forget about the imperial/metric thing for now)







Off to the shed to experiment with a bit of wood!


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## artie (16 Nov 2020)

JoeSheffer said:


> I think actually what i might have been doing wrong is measuring centre to centre.


You've cracked it.
It's always better when you figure it out for yourself.

Imperial or metric matters naught, except when the merchant sends 2400 by 1200 sheets when you've prepared for 8 by 6 . 
That was a hateful day.


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## Cirks (17 Nov 2020)

The interesting bit for me is that if you’re using 8x4 on say the outside of a stud/frame structure BUT also on the inside, then the measurements of 16 on centres only really works on one side doesn’t it due to having a corner take up ~3” (for 3x2 timber) on the inside.

| | | Studs at 16c fitted 8x4 on outside
_ Inside loses width of side wall studs so no longer 8x4 ‘compliant’
_
_
Studs on other side wall


Rubbish drawing/explanation!


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## Lons (17 Nov 2020)

Cirks said:


> The interesting bit for me is that if you’re using 8x4 on say the outside of a stud/frame structure BUT also on the inside, then the measurements of 16 on centres only really works on one side doesn’t it due to having a corner take up ~3” (for 3x2 timber) on the inside.
> 
> | | | Studs at 16c fitted 8x4 on outside
> _ Inside loses width of side wall studs so no longer 8x4 ‘compliant’
> ...


I don't see the problem. you just start at a centre stud and trim the sheet back to the corner where extra support is fixed as necessary. I would never unless unavoidable join internal and external sheets on the same stud anyway.


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## Cirks (17 Nov 2020)

Hi - yes, I know how to do it but it's quite funny that it's never mentioned (or certainly not in any YouTube stuff I've seen about framing walls etc...


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## Lons (17 Nov 2020)

Yeah sorry I didn't mean to imply you didn't know as it's basic stuff and commonsense.

As useful as Youtube can be it certainly isn't the font of all knowledge and is also a source of a large amount of misinformation and individual posturing, there's a lot to be said still for the old tried and tested literature.


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## TRITON (17 Nov 2020)

Ive never put centers down to exacts, if you want them closer or further apart do that. Mostly its studs for external sheds and the like, but I suppose internal and at a later date anyone hanging anything from it might encounter studs not being where they thought they were, but that said again, working in older houses, its usually a job to fine one and another to find the bloody one next to that.

I work primarily in mm too, but I gauge heights, lengths in an approximate feet and inches. 
I did read something years back that the British citizen is almost hardwired to imperial, so when they want something, its like Oh about 5 feet, or about 8' long, and then work out the exacts in mm.


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