gb484
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« on: July 07, 2009, 09:57:18 PM » |
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I would like to make my own I-beams for a renovation project, floor joists and rafters. Anybody out there done it already?
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Mark Fisk
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« Reply #1 on: July 07, 2009, 10:43:05 PM » |
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Haven't done it as yet but having used manufactured ones in a barn conversion project and thought that they would be simple to construct if you had a table saw and a good collection of clamps. I would use osb, (oriented strand board), for the web and regularised softwood for the top/bottom, I think any large knots should be cut out and then joined using a finger type joint which can be done with a high power router. Good luck!
Mark
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desperate
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« Reply #2 on: July 07, 2009, 10:49:35 PM » |
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Hi gb484
I asked an engineer weather we could make a lattice beam on site for a loft conversion we built, instead of lugging a load of steel up to the top, he reckoned it would be a technical nightmare proving them to the satisfaction of bldg control and not to bother, I,ve no idea if joists and rafters would be the same challenge, but I would ask for advice from a struct eng as step 1
Desperate
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Richard Owen
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« Reply #3 on: July 07, 2009, 10:49:56 PM » |
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I assume we're talking timber here?
C beams are easy.
I's are a little more tricky. It might be worth getting some prices to see whether or not it's worth it.
Also check with building control. When we used timber I-beams they wanted to see the engineer's calculations. This wouldn't have been possible with home made ones.
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AlanM
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« Reply #4 on: July 07, 2009, 11:31:12 PM » |
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What dimensions are the beams to be. If a renovation what was there originally, or are you increasing spans from existing?
Alan
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gb484
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« Reply #5 on: July 09, 2009, 03:43:27 PM » |
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The beams for floor joists would need to make a first floor in a small house and would need to span 4m. The beams for the roof would be about 5-6m long. Because of the lack of headroom in the upstairs space, I would like to dispense with purlins if possible and use the I beams as rafters to take the roof, putting plenty of insulation between the beams. I thought I might make the beams 350mm deep out of OSB, with treated timber either side of 25x45mm, depending on what I can find at Wickes.
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Justme
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« Reply #6 on: July 09, 2009, 05:19:29 PM » |
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Do you realy need I beams for that?
I thought there were for when real timber could not be supplied long enough or deep enough or if weight was an issue. I dont think 4-5-6m long & 350mm deep is a problem for normal timber. Do you really need 14" deep? As you have space issue real timber could be much smaller than that.
Justme
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gb484
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« Reply #7 on: July 10, 2009, 05:53:11 PM » |
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Maybe not. My main aim is to be able to dispense with the purlins.
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desperate
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« Reply #8 on: July 10, 2009, 07:40:07 PM » |
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hallo gb484
rafters without purlins are going to be big beasts at 5-6m span and also are going to put a lot of twisting force onto the wall plates, you might end up needing collars instead. It sounds tricky to me.
Desperate
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KLD
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« Reply #9 on: July 10, 2009, 07:56:21 PM » |
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Could you install a (steel?) ridge beam? That would take away the pushing and twisting forces on the wall plate / the wall. Six meters are still awfully long. The TRADA span tables only specify up to 47x150mm rafters, and the max span is between 3.50 and 4m.
Klaus
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Richard Owen
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« Reply #10 on: July 10, 2009, 08:29:38 PM » |
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The traditional way to resolve the horizontal forces at the wall plates is to make trusses of the rafters and a horizontal beam. The triangular shape resolves all the horizontal forces leaving only the vertical ones to bear upon the walls.
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KLD
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« Reply #11 on: July 10, 2009, 08:36:49 PM » |
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Richard, I didn't understand what the OP meant with "limited headroom" and freely interpreted that as meaning the building is 1.5stories, so the wallplate is at chest or shoulder height in the upstairs. Makes for an awful lot of ducking with the horizontal binders every 400mm  Klaus |
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Richard Owen
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« Reply #12 on: July 10, 2009, 10:04:56 PM » |
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Missed that bit.
It is possible to use the horizontal on a 1 1/5 storey to stiffen the truss. I know 'cos that's what we did on the extension.
Needed some hard sums from the engineer mind.
Not sure I'd diy.
Richard
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desperate
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« Reply #13 on: July 10, 2009, 10:10:30 PM » |
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Richard
Them,ll be collars then? usually 1/3 ridge to wallplate height down from ridge, but still need a purlin to stop standard sized rafter sagging.
Desperate
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Richard Owen
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« Reply #14 on: July 10, 2009, 10:20:39 PM » |
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We used I-beams. Which I think I mentioned above? Probably not clearly enough.
No purlins.
No ridge board either. Felt very odd putting the trusses up. Worked well though.
Big fan of timber I-beams, me.
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