Bearers and joists

[Bemboka]

I'm designing a (small) house for my block at Bemboka. Two storey, 8,000mm x 10,000mm out of timbercrete. I'd appreciate some input on bearers and joists for the the second level tongue and groove floor. I'm after a really minimulist look - so upstairs floor is the downstairs ceiling and the timberwork is all exposed.

Anyone had much to do with this ? My problem is what (if any) bearers will spand 8000mm, what centres they would need to be and what joists would work.

Any comments or ideas greatfully received.

[ozwinner]

If you need to ask about bearers and joists for the upstairs, you are out of your league.
Get some proffesional help, I.E, a builder.
Same for spans of 8 metres.

Al :eek:

[DavidG]

Hey Al. Occasionally you actually say something sensible.
You must be getting old and having senior moments.

[ozwinner]

Hey Al. Occasionally you actually say something sensible.
You must be getting old and having senior moments.

Ok,ok, am I the pot or the kettle??

Al

[DavidG]

Ok,ok, am I the pot or the kettle??

Me looks down and has trouble seeing toes. Thinks "I am the pot" (bellied) therefore you must be the kettle.

[ozwinner]

therefore you must be the kettle.

Sorry, but I am a teapot.

Al

[ausdesign]

I agree with Al. Only trying to be helpful but I've never come across exposed bearers & joists - exposed joists yes. and if your asking the question then you should speak to someone.
Hyspan 400*63 joists at 450 centres will span 8.2 without loadbearing walls above - i.e. a truss roof - but it will require blocking between the joists to prevent twisting.

[DavidG]

Sorry, but I am a teapot.

Al

Ok. That make me the Kettle. Wheeeeeeeeeeeeeeeee.

[Bemboka]

Thanks Peter. Sorry I didn't get the jargon all correct. Thought the idea was to be able to ask for help here. I have read a bit about Hyspan - for rough budgeting purposes what should I allow for them ?

[silentC]

Rude buggers, aren't they

Bemboka is about half an hour from where I live, up in the foothills of Brown Mountain. Getting a bit trendy up there

While hyspan will do the job, it's not going to be very pretty from underneath. I also wonder about noise if you're going to be looking at the bottom of the floorboards. Maybe you could use Hybeam instead and line the underneath with tongue and groove panel or something.

[ausdesign]

No hurt intended. I tried to phrase the reply sensitively.
Hyspan is the main product I have knowledge of & am comfortable with specifying for extremely long spans. Shorter spans I would be looking at F17 seasoned hardwood.
Other alternatives are posi-joists or running a bearer (beam) to break up the span to enable smaller joists (lesser span) to be used but in both of the above, being an exposed ceiling I would go for a deep joist to make the appearance ok. - You would possibly be looking at a steel H section as a bearer to span 8 met.
If there are walls on the lower storey that you can span from, then F17 may be an option. -240*35 F17 will span 4800, 300*50 F7 oregon will span approx.4800.
The main consideration I would be looking at with deep jiosts is to use a seasoned timber for shrinkage reasons.

[TassieKiwi]

..well that's what I first thought it read.

[Bemboka]

The concept is to have the lower area as large as possible. We can run a wall across at 3000 - making two spans of 5000 and 3000. But the ideal was to make all internal walls non-load bearing so we could move them around later as the house grew.

It's a matter of economics I suppose - whether steal bearers and "smaller" joists (that would give me exposed bearers and joists wouldn't it !) would be more economical than simply large joists.

Have you had any experience in working out the economics of this ?

With regard to noise - we're really not worried at this stage as it's just the starting point for a larger house when we retire.

Thanks for your constructive comments.

[ausdesign]

Bemboka, another aspect to take into account is the bracing requirements for the lower storey.
As an example for a site classified as an N2 wind category there needs to be walls with bracing calculated on the length and height of the external walls at 9 met spacings at right angles to the wind direction. i.e. at right angles to the long & short side of the home. The type of bracing must attain a specified level of Kn resistance in both directions. This may sound more complicated than it is, but basically it would be nearly impossible to design a home 8m*10m without structurally braced lower storey internal walls. Food for thought with your lower storey layout.

[Bemboka]

Good point - that's where discussions like this are a good opportunity to learn. I suppose I could go 9,000 x 8,000 instead of 10,000 x 8,000 if that simplified things. The later was somewhat of an arbitrary starting position anyway.

By the way - the load bearing walls will be "Timbercrete" - which are 400mm x 200 x 180 mm load bearing blocks.