Distance between centres for ceiling?

[Waldo]

G'day,

I'm about to build an office within my shed and my question is what distance should the centres be for ceiling rafters to bear the load of gyprock sheeting? The ceiling wil be 3700 x 2800.

Secondly what distance should the noggins (?) be set at within the rafters? Or do I just run rafters?

[journeyman Mick]

Waldo,
that'd be ceiling joists and battens (rafters are those raked bits that hold the roof up ;) ) Joist spacing would depend on the joist dimensions and timber grade as well as their span. Battens can be at 450 crs for standard 10mm plasterboard or 600 crs for 13mm or apparently there's 10mm ceiling plasterboard now that will span 600.

Mick

[Waldo]

G'day Journeyman,

Thanks for the clarification, knew what I was on about but the terminology was wrong. Thought it was 600 crs which is the same for wall studs but 700crs was also in my head. I'll use 13mm p/board.

Can you give me a pointers to "Joist spacing would depend on the joist dimensions and timber grade as well as their span"?

[Skew ChiDAMN!!]

Errmmm... posted the following in another thread, then decide to delete it (inappropriate thread) and paste it here. :o



G'day Skew,

I won't argue with that, the dirty bit that is. Longer, well depends if I have a large pitch I'm working on, then the nights become days and so on. ;)

To change the subject any ideas on this? My head is a bit rusty on it and trying to remember what I was taught by my Dad.

http://www.woodworkforums.ubeaut.com.au/showthread.php?p=300983

I'm also looking for diagrams showing the correct method of fixing rafters to wall frames, by that I don't mean nails etc. I know the bulk of it, just can't remember if I'm right or not.

Mick's already answered the centres question. Rafters, I usually just use gang-nail brackets unless otherwise spec'd in the plans. They're legal down here, don't need fancy tie-downs 'cos were not rated a cyclonic area. Joists onto top-plates are becoming a rare thing for me, now that trusses are becoming the norm. Joists are just hung under the trusses (again with gang nails) with alum battens simply screwed on and the top plates stop an inch or so from the ceiling ! :eek:

I prefer the old ways better.

And what I meant by the harder/longer/dirtier thing was: who'd win between a housewife with toddlers and a 12on/off 12 pit miner? Both would... in their own eyes. Purely a subjective thing... every job has it's downers. [shrug]

[journeyman Mick]

Waldo,
if you run your joists so they span 2800 they won't be working as hard as if they were spanning 3700. Can't tell you sizes off the top of my head as I've never pitched a roof that didn;t have exposed rafters, everything else has been truss rooves. Too late to go and find a book and look it up now, maybe one of the more err, "chronologically advanced" chippies can give you ceiling joist dimension.

Mick

[Waldo]

G'day,

Thanks Skew and Journeyman for your help tonight, time to call it for a night and I'll pick up again in the morning.

Probably the best bet is saunder across the road to my chippie neighbour with some ales and pick his skull. Just wanted to find out what I'd forgotten and needed updating on, so thanks fellas you've both been a good help.

Strewth 12:27am! :eek:

[ausdesign]

100*50 f8hw spans 2400mm at 450 or 600 centres
125*50 spans 3000 at 450 or 600 centres
150*38 spans 3600 at 450
150*50 spans 3600 at 600.

[Waldo]

And what I meant by the harder/longer/dirtier thing was: who'd win between a housewife with toddlers and a 12on/off 12 pit miner?

G'day Skew ChiDAMN!!,

Ahh. "It all makes perect sence, expressed in pounds, shillings and pence"

[Waldo]

G'day Ausdesign,

Thanks for the info there. Another question, would you run battens between the joists or not? I ask this as it seems that both ways, from what I can find out, are acceptable.

[journeyman Mick]

Waldo,
I've worked on older places where the battens were cut in between the joists, but unless you're really desperate for the extra 30 or so mm of headroom it's a lot more work. This is for an office in your shed right? How much room betweeen the top of the ceiling and the roof? If there's a bit of space you might want to go to much bigger joists so that you can put some ply or particleboard flooring on top for more storage space.

Mick

[ausdesign]

No battens are only used to make the spacing of 450 or 600.
i.e if you were using deep ceiling joists to span long distances then you may have them at say 900 centres & not 450 or 600 (to cut down on cost) and then you would run battens at the correct spacing.
Typical situation is where you run roof trusses at 900 centres & then fix timber or metal battens to the bottom chord at 450 for 10mm plaster or 600 for 13mm plaster.

[Waldo]

G'day Journeyman Mick,

There won't be much height for the ceiling as I can only run it to the bottom of the shed trusses which are 2300 heigh and angle line struts running at an angle and fastened to the purlins (or is that girts?). So really there isn't any space because of the angle line. All up there might be 200mm of space.

I'm planning to run ply on top for some storage space.