Engineered wood (I-Joist, LVL) Versus Solid timber joist

We are adding a first floor to our house. Builder has recommended that we can use engineered timber products such as "I-joist" or pay more for "LVL" for joist. We actually prefer to use "solid timber" rather than engineered wood because we believe solid timber is more water resistant and stronger overall. Builder said no one uses solid timber anymore for joists and he doesn't even know where to get them anymore.

I've seen new houses being built, and the majority do use I-joist...

Is the builder correct that we should stick with engineered timber products? and there is no benefit of solid timber anymore?

Note - cost is not a driving factor unless we are talking about doubling or tripling the cost to use solid timber joists.

100% I joists, greater spans, you can cut a fair size hole in them for air-con ducts, plumbing etc. Straight as well and fairly stable with expanding and contracting. Very rare to do a sub-floor in solid timber now

very rare to use solid timber because of cost? or is solid timber an inferior product compared to engineered timber for joists?

I thought at least solid timber is more water resistant than engineered timber.

definitely I joists, dead straight and stable.

F graded Solid timber has strength variation between sticks so difficult to ensure they won’t deflect. veneer based joists like I joists and LVLs average out these variations.

Water resistance is not relevant indoors

Much more environmentally friendly too

You can also check out concrete suspended slab floor e.g. with Speed Floor, Bondek or similar system. Much better from acoustic insulation standpoint, but also for passive solar heating.

I was thinking about water resistance under the bathroom. Will I-Joist be risky in those areas?

I am just trying to determine the best material to use. Cost is not an issue (to an extent). Sounds like F graded solid timber (as joist) is becoming obsolete because it is an overall inferior product?

Wouldn't Concrete flooring be too heavy for my first floor addition? Haven't really considered using concrete flooring.

Do you have timber framed walls or double brick?

This is why you would have to do waterproofing over OSB to prevent water ingress.

You wont have any water issues with LVL's or I joists for that fact. as the earlier poster said the modern products are engineered to be stronger, straighter and have far greater spans.

also with modern waterproofing the bathroom will outlast our own lifespan.

but as alex said, if you can afford it, go with bondeck. Cost difference will probably be around $100/sqm but a far better result

cheers

Simeon

www.ashingtonhomes.com.au

great reply, very very true

My experience with engineered joists and LVL is that they have greater bounce
I have used engineered joists throughout my home 14M span over several walls but in the kitchen I added 2x 300 KDHW F17 solid joists to reduce bounce, all good.
Just get your engineer to check design for bounce.

what centres were they at?

450 centres but engineered timber joists for some reason have greater dynamic deflection than solid timber. Most builders and engineers are not aware of it. I know because we had couple of jobs with excessive bounce and we fixed it by adding solid beams.
Engineer typically will only do static calculations and miss dynamic altogether.
On long I spans I always recommend 2 rows of herringbone strutting to stiffen up.

Thanks for the advise. Do you only recommend using F17 solid joists in high traffic areas (such as your kitchen) rather than the entire floor?

I will ask the builder about bondeck. Will it be too heavy for my existing brick veneer foundation?

It depends, bounce in bedrooms or lounge may not matter but you don’t want your plates and glasses rattling in the kitchen when you walk.
It depends on design, spans and use.

https://www.tilling.com.au/wp-content/u ... 8.web_.pdf

this has a good section on dynamic performance.

I joists are light, LVLs will have better dynamic performance as they are heavier. 300mm F17 hardwood is nice but probably comes out of a beautiful big eucalypt whereas the LVL is plantation grown pine. The eucalypt would be better used as a nice table or something, in my opinion, still the F17 is nice stuff

i would have thought LVL joists would be at least as strong as solid timber
am i mistaken

Yes they are just as strong but I was talking about bounce