How far apart are ceiling joists in Australia

Table of Contents Show

What are ceiling joists and beams?
How are joist and beam style ceilings constructed?
What are the different parts of joist-style ceilings?
What are they clad with inside houses?
What are the load bearing capabilities of ceiling joists?
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Distance between centres for ceiling?
Ceiling Joists
How wide are ceiling joists spaced?
How far apart should ceiling joists be?
How far are ceiling beams apart?
How do you find a ceiling joist without a stud finder?

Ceilings in most modern homes use wooden joists and beams.

What are ceiling joists and beams?

In regular light-frame construction and conventional roof framing, the ceiling is constructed using an arrangement of timber joists and beams that run across the length and width of the ceiling. Other materials, such as metal and concrete, may also be involved in making a ceiling. Joists and beams create the ceiling of a room, and support the ceiling cladding (the part that's visible). Ceiling joists also help to anchor the walls to prevent them from collapsing inwards or outwards, and help to keep the roof up.

How are joist and beam style ceilings constructed?

Constructing ceiling joists is part of the overall process of building the frame of your home. Once the wall framing has gone up, the ceiling joists can be put in place. The joists run horizontally between opposite walls, and attach to the tops of the walls with a wall plate. Building regulations dictate how many joists need to be installed, the distance between them, and how thick they should be. Once the joists have been constructed, other beams are installed which help support the walls and roof of your home.

What are the different parts of joist-style ceilings?

Conventional frame-style ceilings are typically built using three main components. These are:

Joists - These are the horizontal members that run from wall to wall.
Hanging beams - These run perpendicular across the top of the joists to join them together.
Strutting beams - These sit in between the joists to support the roof struts.

What are they clad with inside houses?

Typically, the ceiling joists and beams are clad with plasterboard to create a flat surface for your ceiling. Other materials can also be used to clad the joists and beams, including metal and timber. There are many options for ceiling finishes and cladding.

What are the load bearing capabilities of ceiling joists?

Unless you have a flat roof, the ceiling joists and hanging beams are in place to support the ceiling only. They will not support a pitched roof load - this is the role of the strutting beams.

Advantages

Standard framing process with few surprises
Relatively cheap
Options for future modification

Disadvantages

Lack of individual character
Potentially bland ceiling finish

The ceiling joists have a double function:

they provide the structure onto which the ceiling is fixed
they are the member that connects or ties the lower ends of rafter couples (pairs). Therefore, they prevent the rafters spreading and causing the roof to sag or collapse.

Ceiling joists are normally horizontal members, however, under special circumstances they can be fixed on a slope. They are spaced according to the material they support. Typically the material is plasterboard which can span 450 mm.

For coupled roofs, ceiling joists have to be in single lengths or spliced. They must be at the same spacing and in the same direction as the main rafters so they can be fixed to, and act as ties between the feet of opposing rafter pairs. Where there is no internal wall to support the ceiling joist a hanging beam must be installed.

Any opening, manhole, skylight and similar must be trimmed to provide full support for ceiling linings.

Refer to the Table 21 of AS 1684.2 for details about the required spans for ceiling joists.

1st May 2006, 11:25 PM #1
Distance between centres for ceiling?

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?
I make things, they just take a long time.
1st May 2006, 11:54 PM #2

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
"If you need a machine today and don't buy it,
tomorrow you will have paid for it and not have it."

- Henry Ford 1938
2nd May 2006, 12:08 AM #3

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"?
I make things, they just take a long time.
2nd May 2006, 12:15 AM #4

Errmmm... posted the following in another thread, then decide to delete it (inappropriate thread) and paste it here.
Originally Posted by Waldo
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...d.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]
2nd May 2006, 12:21 AM #5

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
"If you need a machine today and don't buy it,
tomorrow you will have paid for it and not have it."
- Henry Ford 1938
2nd May 2006, 12:28 AM #6

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:
I make things, they just take a long time.
2nd May 2006, 07:57 AM #7
Ceiling Joists
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.

Peter Clarkson
www.ausdesign.com.au
This information is intended to provide general information only.
It does not purport to be a comprehensive advice.
2nd May 2006, 10:21 AM #8

Originally Posted by Skew ChiDAMN!!
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"
I make things, they just take a long time.
2nd May 2006, 10:23 AM #9

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.
I make things, they just take a long time.
2nd May 2006, 10:30 AM #10

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
"If you need a machine today and don't buy it,
tomorrow you will have paid for it and not have it."
- Henry Ford 1938
2nd May 2006, 10:47 AM #11

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.
Peter Clarkson
www.ausdesign.com.au
This information is intended to provide general information only.
It does not purport to be a comprehensive advice.
2nd May 2006, 10:48 AM #12

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.
I make things, they just take a long time.

How wide are ceiling joists spaced?

Joists are spaced evenly, typically 16” or 24” apart across a broad surface.

How far apart should ceiling joists be?

Related Articles. Ceiling joists are usually installed either 16 or 24 inches on center, which means roughly 16 or 24 inches apart. Once you've located the first one, the others are easier to find. If you only need to know which direction the joists run, access the attic and take a look.

How far are ceiling beams apart?

Ceiling beams are typically spaced between two feet and eight feet apart. The most common ceiling beam spacing is four feet apart. Ceiling beam spacing is a matter of preference so there's no right or wrong answer!

How do you find a ceiling joist without a stud finder?

Hammer a small nail into a popcorn ceiling 16 inches in from the wall to test for a joist. Stud finders measure density to find beams, so they don't work on popcorn ceilings.