Posi-joist, or easi,eco,lattice etc.

[Tim Lamb]

Has anyone considered/priced d-i-y lattice joists?

I need to replace the timber roof joists on one of my flat roofed barns. Span about 18'0 so not trivial in timber. The existing rolled steel sheet could go again and be fixed to 100x47 purlins at 4'0" intervals with 1/2" shuttering ply under and 75mm PIR foam between. Or stretching the budget, new twin wall insulated sheet.

I suspect finding the correct grade of timber, buying the steel webs and assembling will not bring a huge saving over putting the job out.

any thoughts?

[meow2222]

Its unclear exactly what youre looking at making

NT

[Tim Lamb]

These things..

[Jon Fairbairn]

Would JJI joists do? I tried to get some when boarding out my loft, but they wanted a much bigger order, so probably not for you either. On the other hand, making something of that style would probably be cheaper and easier than lattice joists.

[Tim Lamb]

I could make those as well:-)

Finding C24 timber in 5.5m lengths might be tricky. Sadly their load chart does not offer roof figures.

Somebody on E-bay was selling the metal webs for £1.00 ea. so unlikely to be a cheap solution. I like the idea of the open web for service access although you can also drill largish holes in the JJI Sterling board.

>

[meow2222]

OK, I'll keep it general. Timber webs are easier to make and far cheaper t han steel. Set up a mitre saw with an angled end stop and you can cut them up pretty fast. They can be made from some firewood, green roundwood, banan awood etc. Web end fixings are the weakpoint, with splitting being the main risk, so they need to be thicker than would appear to be required for stre ngth alone.

Any such structure has to be tested before use to ensure adequate load rati ng. If you want to know what broke and why, you need a high frame rate came ra, as failures typically consist of a fast chain reaction of failures, mak ing it impossible to determine just by inspection afterward.

Where timber has to be joined, you can wrap the epoxied finger joint with e xtra timber around 3 or 4 sides, all glued & screwed every 6".

NT

[Tim Lamb]

In message , [e-mail] writes

er? I take your point about timber being cheaper than metal but a web of Sterling board sounds easier still.

Before anything else, I am going to check the nettle patch for long steel beams:-)

[GMM]

Not a metal web but everything you didn't want to know various timber composite beams:

I was thinking of doing something like this for my new loft joists, assembling on the top floor from overlapping 8' lengths because of access problems. Currently engaged in improving access in the hope I can get some real timbers up there, instead...

[meow2222]

That's the doc I was looking for, but failed to find. Bear in mind the injected foam has a bit of stabilising effect on the sheet.

NT