PosiStrut vs HY Joist

Hi All,

We've started our new house build and I have a newbie question that I can't seem to find much on google about exactly. I hope someone here is able to shed some light and educate us.

In our engineering plans it states the use of either PosiStrut or Hyjoist and our builder has selected to use HY Joists.

Whilst we're not too fussed with either (assuming the structural outcome is the same for both), however a friend has criticised the decision of not going with PosiStrut and that our build has gone down the 'cheap' path.

My question is - is there much of a cost or quality arguement between the two?

Hope someone can help!

I had a similar query, but it was never fully resolved. Hard data is difficult to come by, but PosiStruts have a better reputation than Hyjoists for being more resistant to floor vibrations (something that I'm very sensitive to). In theory, if everything else is equal and they're build to similar specifications it shouldn't matter, but it seems to make a difference in practice, possibly because PosiStruts also have the advantage that they can be tied together with strongbacks, which increases stiffness and minimises vibration.

My own anectodal (and subjective) experience from visiting multiple construction sites was that I could feel a difference in favour of PosiStruts, but note that there might have been other factors involved as well.

We went with PosiStruts (over our builder's default HyJoists), with a floor specification of 2.0kPa live loading instead of the 1.5kPa Australian residential standard (international standards for housing construction are more in line with 2.0kPa, and after experiencing many double-storey Australian houses I think the Australian standard is is a bit light-on), and using Hebel PowerFloor. Our build is still under construction, but it's already clear that our uncovered and unsheeted upper floor is a lot more rigid and solid than many (most?) Australian upper floors. Again, though, how much is due to the PosiStruts alone is hard to say for certain.

Thanks for the response and sharing your experience algernon!

I did notice some vibrations but we don't have access any building sites using PosiStruts to compare with - I was thinking it felt much better than the place we're in now and didn't think any more beyond that.

We would have gone the 2.0kPa loading if we had known about it, a definite upgrade item for the next one (hopefully not too many years down the track).

Do you mind me asking if there was a price diff? (Not sure if you'd know given most builders don't provide detailed breakdowns)

Thanks heaps again!

I personally like Hyjoists better and have used them on my house mainly because you can span them from one end to the other (in my case 14m) and are easier to handle. Running over walls as continuous beams they are stronger than simply supported beams.
However there is an issue with dynamic deflection (bounce under live load) with Hyjoists and with LVL) and I always recommend 1 or two rows of herringbone bracing on long spans.

Sorry for the late response - I can't give you a specific price difference, sorry (our builder does provide detailed breakdowns, but there was a bit of drama when the original frame and truss manufacturer went under the week before things were due to be delivered, and all our original price comparisons went out the window). Based on our earlier comparisons with other manufacturers it wasn't adding too much in the grand scheme of things (a couple of thousand $ maybe?).

Thanks building-expert and algernon.

I guess pricing won't be much of a factor if it's just a couple of k's difference!

I'll see if we can get some herringbone braces in as we're yet to plaster. I hate the slightly bouncy feel (like our current place)