Bearers supporting internal non-load bearing walls.

[manofaus]

la de da... designing a house... getting to the sub floor. The frame of the house will have all external walls as the load bearing walls. The roof will be trussed.

Do i need to make sure that the foundations (bearers) are in line with the internal walls where possible? My piers will be rather expensive each and I think it would be cheaper to upgrade the timber size in the bearers and joists instead of making more piers. It would mean that I would have a piers in the middle of the hall. The capacity of the bearers is at 2 and rigidity is at 2.6. (2.8 span, 2.5 spacing) By doing it this way I save about 1800 bucks in materials alone.

[Bloss]

You need to design to BCA . . . saving 1% or so on the capital cost of a structure built for 50 years and more is false economy, but upping timber sizes can work - but up a lot - minimum standards are never best practice!

[manofaus]

well the timber selected is double its capacity and more then double its rigidity as per span charts which I would assume comply with the BCA... is that an incorrect assumption?
Is it a BCA requirement that all non load bearing walls are directly supported by piers? (walls have to be directly in line with piers?)

[barney118]

Assuming its a single storey here, bearers are there to support the subfloor on internals, and transfer roof loads on external bearers to the foundations. a double joist is placed on outside and internal walls. need to leave gap on external joists for fitted floor so you have the flooring on half the inside joist, if using platform floor you can butt joist together.

[intertd6]

you dont have to have the internal bearers under any internal walls as they are non load bearing if you are doing a platform floor.
regards inter

[manofaus]

thanks

[manofaus]

I am getting closer to the design slowly. Is a platform floor one where you place all your joists at their centers then cover with chipboard flooring, then you stand up the internal frames on that? I am weighing up the cost of doing it like that compared to 'double joists' under the internal walls.

[Bloss]

I am getting closer to the design slowly. Is a platform floor one where you place all your joists at their centers then cover with chipboard flooring, then you stand up the internal frames on that?

I don't know many who do not use 'platform' construction nowadays - so the answer is yes, but depends. As always timber framing is horses for courses - fully trussed roofs usually (but not always) use perimeter load bearing ie: to two or more external walls which will be sitting on double joists, but there are wide variations and all work fine. One can use CAD systems to get mixed structures - a mix of conventional roof and trusses for example - you can build pretty much why you want now - just meet BCA.

[manofaus]

thanks bloss.
just weighing up the extra joists vs the flooring at this stage.

[Bloss]

thanks bloss.
just weighing up the extra joists vs the flooring at this stage.

That's the wrong measure - the labour costs are why platform mostly comes out ahead. And if DIYing you shouldn't make the mistake of thinking your time is 'free' - all time is valuable, the question is what are the alternatives for using it and what comparative value do you place on each (and like land - they ain't making any more of it!).

[manofaus]

We are looking at spotted gum for flooring. I would assume that you don't make a platform out of this? Or is it a case of standing up the external frames and getting the house to lockup then once the flooring is layed doing the internal walls on the spotted gum? That actually sounds easy to put the flooring down, no cutting around internal walls.
but in actual fact i think what you say usually happens, is the bearers, then the joists, then the green/yellow tongue flooring, then the framing, then the spotted gum..

[barney118]

I think it is still good practice to use double joist under walls and obviously around the perimeter. For the sake of a few extra lengths the cost is negligible, and
i would prefer to nail the wall plate through the Y/T into a joist on the platform construction.

[Bloss]

:whs: but not all that easy to work out where for a DIYer unless included in detailed drawings. Perimeter usually done in any case even on edges which have not load-bearing walls, but depends on drafting.

[manofaus]

about a $1000 for the extra joists...

[Bloss]

in actual fact i think what you say usually happens, is the bearers, then the joists, then the green/yellow tongue flooring, then the framing, then the spotted gum..

:2tsup: