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Hi Guy's
My structural approval gives me a choice of either running a fairly major Hyspan Timber ridge beam or alternatively I can use a steel 'I' beam.
The timber option is staright forward although its quite expensive hard to source because of the size. The question is ... if I were to go the steel beam option, what would be the best meathod for attaching rafters to the beam (you can't just nail)?
Any ideas what the norm is?
G'day OBBob
The normal method is to weld cleats every 450mm for the rafters to bolt to. You can either have the cleats on top or inside the beam so that the rafters sit on the lip on each side of the beam. Also the correct name for an "I" beam is a Universal Beam :p Commonly called a UB or if its a post it's a Universal Column commonly called a UC
Well I think having that manufactured would probably belittle the Hyspan price, plus it would be heavier and harder to install.
Check the structural plans for the connection details, often you can bolt a timber plate to the steel beam or use a ramset gun, steel beams are better when space is a problem.
I bolted a timber top plate to the top of the beam and then nailed/triple-gripped my trusses to that. I guess you could do something similar.
Under my house in the Garage i have a UB about 300 x 150 and 6 metres long acting as a bearer for 2 above floors, including the walls above. I'd hate to imagine how big a timber beam would be. On top of this is bolted a 4x2 which the joists are nailed into. This is bolted down every 900 mm (staggered to either side of the middle) The bolts are only loose, I can undo with my hand. The holes in the UB are slightly larger. This i think is to allow for the small differnece in expansion and mainly to stop the 4x2 falling off the side.
I used a similar method on a balcony that I built. Using PFC (C shape) and 4x2 on top. The engineer initally specified cleats, but 23 joists = 46 cleats = a lot of work. He agreed to the 4x2 method. To have the one for the balcony done required a half dozen guys, a BBQ and a few beers.
A neighbour of mine had the stumps under his house removed and relaced with a few very large UB and the bearers had PFC bolted to the side before the stumps were removed. The PFC was done with 3 of us. 2 lifting and one putting up props. The major beams requried a dozen guys and a spare hour or so.
Greetings OBBob can you give some expansion on your project ?
Hi Peter
Things have moved quickly today. The timber suppliers weren't being a lot of help but I have taked to the beam manufacturers and now understand the problem.
The intention was to use a very large LVL (600 x 63) as a ridgebeam (cathedral ceilings), however the uncommon size meant that they would only manufacture it if I was to buy two ... this is because they rip the wood at 1200 to laminate the beam ... then they would be left with a 600mm beam they couldn't sell.
Anyway, it appears aside from steel the better option is GL18, which is rated at F27 and can have a camber put in it ... thus the profile is smaller and cost is significantly less.
I probably deserve what I get because I should have kept it simple and used trusses but it appealed to do something a little different given the amount of work I have put in.
What would your suggestion be for such a design?
OBBOB
Is there a chance of using intermediate supports or do you absolutely require a clear span? I used in, a similar situation to you, Ironbark beams 300 x 75 between 3m and 3.3m long. They were still heavy, actually very heavy in that I could hold them but not even lift them above my head. Around 80kgs in an awkward shape.(heavier than me!)
I did place them by myself as ridge beams, admittedly using an improvised boom from the back of a tractor.
If you are using a beam 6m to 9m in length, you will definitely require special lifting arrangements. A crane for one hour (you must be exactly set up) will not be that much.
Regards
Paul
Thanks Paul
Actually I have spent many a sleepless night working out how to go about this ... so I don't really want to change the basis of the design. If the GL18 comes through then I think I'll be sorted.
As for lifting it I think I have that aranged too.
It's been a big learning curve but that's why I wanted to do it!
Understood. Particularly the sleepless nghts. Best of luck.Quote:
Originally Posted by OBBob
Regards
Paul
Like Silent says fix a timber plate to the beam. Either bolt it or Ramset nail it with a power actuated tool and then just use triple grips. Probably have to use a black charge and hang on like hell. Fix it while the beam is on the ground. It's a bit hairy up in the air.