hyjoist for subfloor

Hi All and apologies for this possibly stupid question :oo:... We recently rented a shop where the subfloor had been removed to provide storeage, and replaced with Hyjoist spanning 3.8metres. So this got me thinking, is this was an option for my home renno?

I am planning (no I've not started yet, so you can all sigh with relief :no:) the subfloor of a 4.0mx10.5m ground level extension to the back of our house. Been on the CHH site etc and downloaded the design software (technical for the DIY amateur :-).

Here's my confusion. Does the use of "Hyjoist" reduce the number of stumps required (currently 28 set at intervals 1.5 x1.5 approx.) or is the product merely a replacement for traditional joist timbers?:?
As I am using sheet flooring, do I have the option of 2 bearers (one at each edge) running the 10m length of the space with hyjoist spanning the 4m space at 440mm intervals?
Structurally am I still required to place bearers every 1.5m and stumps beneath them at every say 1.2m if using hyjoist?

In this costing stage of course my interest is to reduce materials costs AND the amount of hole digging. Labour is self inflicted so no further savings there. I should add I am in Victoria so the usual concrete or hardwood stumps are to be used. (too much slope for concrete slab).

Thanks for your interest, what do you think?


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