I-Joist quality. Expectations.

[flanagaj]

I had a load of i-joists delivered 10 days ago and the chippie and I put the joists up today and the quality of them is far from ideal.   As I've never had any experience of i-joists before, I was sorting of expecting sections that didn't resemble traditional timber in terms of straightness or curvature.   Was I naive in thinking that i-joists should be spot on straight and level along their length.   The delta across one 5.5m is around 15mm and the timber used doesn't look like it's been sorted.   When I ask the manufacturer about it today, he told me that the timber is pressed straight as part of the joist manufacturing process.

[SteamyTea]

Composites, which I-Joists are, can suffer from differences stresses which only becomes apparent after they have 'settled'.

There may also have been a manufacturing problem. Hard to tell.

They tend be quite wobbly along their length, but should be dimensionally accurate across the width, and especially the depth, which is where they get their strength from.

Ask the manufacturer for the design tolerances, then get measuring.

[saveasteading]

6 minutes ago, SteamyTea said:

wobbly along their length

That needs to be named after a scientist.

True though. The point of I beams is a reduction in timber used, so the stiffness is lost as a result. Noggins sort it.

It's from a factory so the timber will not have been exposed to the weather. 

Should be fine.

[SteamyTea]

2 minutes ago, saveasteading said:

That needs to be named after a scientist

But what would the derived unit initial be, can't use W.

 

[Gone West]

9 hours ago, flanagaj said:

Was I naive in thinking that i-joists should be spot on straight and level along their length.

I wouldn't have thought so, based on my experience. At my last house, the whole frame was built from timber I-beams and I never saw any beams out of 'true'. They were Steico beams and IIRC the flanges were made from LVL.

[-rick-]

1 hour ago, Gone West said:

They were Steico beams and IIRC the flanges were made from LVL.

 

That was I thought the common construction method. Not normal timber on the flanges. If @flanagaj has found a cheaper make than doesn't use LVL then that might explain things.