I sent back a load of C24 timber as it was twisted and pretty curved. They delivered another batch, which apparently was from a fresh pack. But given the date on the timber was August 2025, I am wondering they haven't just sent more rubbish OR that is the quality that you just have to accept these days. I know it's for a flat roof, but this stuff is 6.6m long and some boards have a curve along their length of 25mm and others have considerable twist in them. Is that acceptable, or should C24 be better quality with straighter lengths and less twisting?

I am now getting slightly concerned, that cutting the main house roof is the simple part and sourcing 47 lengths of straight 6.6m 8*2 is going to be the tricky part of the task. I am now wondering whether trusses might offer better quality control. Given the roof metal standing seam, I suspect that any flaws will show up more than a tiled roof.?

What have others done regarding sourcing timber that for long spans?

Try different merchants. Drive round a few. Look for timber merchants as opposed to builders merchants.

24 minutes ago, Oz07 said:

Try different merchants. Drive round a few. Look for timber merchants as opposed to builders merchants.

I do realise that when it comes to timber, you really do need to go through the pack yourself and pick out the best lengths. That's fine fo shorter lengths, but 6.6m lengths won't go on my Berlingo roof rack 😂

For that quantity and length I think you're onto a loser unless you go and hand-pick the timbers.

Which way are they bent? FWIW over that length I wouldn't be too bothered by 25mm twist or side bend. If it's a bend up/down i.e. the crown as fitted, then that's more problematic.

Not sure on location or how much you're getting them for but after the last couple of projects I wouldn't use anything other than posijoists for something like that. Super straight, regularised, light etc. and for the money a no-brainer.

23 minutes ago, SuperPav said:

For that quantity and length I think you're onto a loser unless you go and hand-pick the timbers.

Which way are they bent? FWIW over that length I wouldn't be too bothered by 25mm twist or side bend. If it's a bend up/down i.e. the crown as fitted, then that's more problematic.

Not sure on location or how much you're getting them for but after the last couple of projects I wouldn't use anything other than posijoists for something like that. Super straight, regularised, light etc. and for the money a no-brainer.

24 minutes ago, SuperPav said:

For that quantity and length I think you're onto a loser unless you go and hand-pick the timbers.

Which way are they bent? FWIW over that length I wouldn't be too bothered by 25mm twist or side bend. If it's a bend up/down i.e. the crown as fitted, then that's more problematic.

Not sure on location or how much you're getting them for but after the last couple of projects I wouldn't use anything other than posijoists for something like that. Super straight, regularised, light etc. and for the money a no-brainer.

They are bent along the crown.

You mention posi-joists being straight, but the ones I recently got from a firm in Southampton were far from straight. Where did you source yours from?

1 hour ago, flanagaj said:

I know it's for a flat roof, but this stuff is 6.6m long and some boards have a curve along their length of 25mm and others have considerable twist in them. Is that acceptable, or should C24 be better quality with straighter lengths and less twisting?

While you shouldn't accept timber that fails the standard, you have to know what the standard says to know whether what they have sent is acceptable or not - and it does permit some twisiting and bowing (which can add up over a 6m length) as well as other defects that you may find surprising.

There's a very brief summary in Section 4 on this page: https://www.site-lynx.co.uk/library/qa-checklists/structural-timber, but you really need to read the full definistions & explanations as set out in the standards (perhaps available at your local library) to successfully argue your case, if there is one, with the Merchant's rep.

For higher quality, it's best to choose an engineered product.