Hare-brained scheme for a hanging beam

I need a hanging beam to support ceiling joists with a 4 metre span. The beam itself has to span 4 metres as well.

I have three 6 metre 90x45 Hyspan joists left over. Looking at the span tables for hanging beams, I would need a 170x45 beam to do what I want.

What I am considering doing is bolting (and perhaps gluing) two of these 90x45s together on edge to form a beam 180x45. Now, I know composite beams can be made up by joining side-by-side but I've never seen them joined on edge like this, possibly for good reason.

So whatchya think?

just don't tell the building inspector and shellberite...

Building inspector? ;)

It's for my new office I'm building in my shed. He's been and gone :D

sounds sweet then.. should work OK

Silent, sounds like it should work but I suspect an engineer would have pink fit! who knows the engineering principles of hispan? if it was solid timber you know that you would be ok, but hispan???

Maybe I should bolt three of them together. It's supposed to be stronger, faster, more able to leap tall buildings in a single bound, than similar profiles in solid timber. It's all held together with glue anyway...

I did tell a small white lie though. I have seen people make composite beams this way with LVL. All they did was glue it with liquid nails and skew nail it every 500mm or so from both side. Seemed dodgy to me at the time.

If I strap around the joists and over the top of the beam so it's not all just hanging off the bottom one, I guess it will be OK.

Sound like your talking yourself around to it. Just issue safety helmets to anyone that enters the room.

Glue the edges with resorcinal glue

OK, I'll buy some on the way home. I've got some Urea Formaldehyde but it's more than 2 years old now, probably should chuck it out.

I too think it will be fine, and safe. If it proves to be "weak" (which it won't) the beam will begin to sag slowly with time. It won't just break in an instant.

Some batten screws, now available in 150mm, after gluing might give you more peace of mind.

Commence to leap tall builings Mr C.

Cheers,
conwood

They do this already as a bought item,and they just have a few gangnails along the length.

Tools

I've made plenty composite beams outa 4x2.
all I did was strap em with hoop iron and bolt 3 sets steel plates with 3/8 bolts. some i just used wood plates when i ran out of steel. they were 4 metre spans and the building inspector laughed his ar#se off and said it aint spec so you'll have to pull it down. i made trusses and everything in that shed. all i had was salvage 4x2 and wall studs. that were 20 year ago. i sold the place a few years ago an the shed still stands exactly as i built it straight as it was the day i done the frame. a lot of this regulation is crap. in the bush we just built with what we had. built light when times were thin built heavy when times were good or we'd wrecked another building or somesuch. you can see em in the bush, old sheds not built to any spec still standing 50 or even a 100 years later.

forget the regs and just do it....it aint gonna crack and fall on your head.

Couldn't get any Resorcinol at the hardware (they didn't even know what it was), so I glued it with Max Bond and clamped it up. Tomorrow I'll run an 8" bolt through it adjacent to each joist. This stuff is pretty rigid. I reckon I could've nearly gotten away with just using one of them.

If you have the timber anyway then I would glue all three together (with Araldite or similar) in a U shape. ie One across the bottom and two upright on top of it. Then bolt it through at 300mm intervals. both through the sides and also top to bottom with BIG washers.
Lets see that one fail

Too late I already glued two of them edge to edge. I figured if it's too flexy once I hang the joists off it, I'll just get up there and glue the third one on top. Some how, I don't think it will be necessary though ;)

Quote:

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Originally Posted by silentC

Too late I already glued two of them edge to edge. I figured if it's too flexy once I hang the joists off it, I'll just get up there and glue the third one on top. Some how, I don't think it will be necessary though ;)

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Why not get some gang nail plates and hammer them every 600mm along the length on each side.

To get the true strength of the full depth of the double beam, you need enough tensile/shear strength in the joint. Not sure if the glue would be enough. Gang nails would help, but are ugly. You can drill vertically through the two at regular intervals then bolt them together with say 12mm bolts - with glue, 500 centres should do it. Use cup head bolts, with the heads down, that way the nuts can be counter bored and hidden whilst the heads would look Ok.

Food for thought.

Quote:

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Originally Posted by dai sensei

To get the true strength of the full depth of the double beam, you need enough tensile/shear strength in the joint. Not sure if the glue would be enough. Gang nails would help, but are ugly. You can drill vertically through the two at regular intervals then bolt them together with say 12mm bolts - with glue, 500 centres should do it. Use cup head bolts, with the heads down, that way the nuts can be counter bored and hidden whilst the heads would look Ok.

Food for thought.

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If it is up in the roof it wouldn't matter how ugly it looks as long as it works.

Thanks Neil, that's exactly what I have done. The beam is up. I've bolted it through with 1/2" cup heads, nuts down. The reason I did that was a) so I wouldn't bang my knees on the bolt ends when I'm up there and b) in case I have to add the third length to the stack down the track. I can undo the nuts, pull the bolts out and replace with longer ones without having to disturb the ceiling.

It's up there and straight as a die at the moment, but I haven't hung anything off it yet.

Silent C What is this joist span book you speak of and where can I get a copy?:confused:

It's the Hyspan span tables. Download as a PDF from http://www.chhfuturebuild.com/WSMApa...0209-1,00.html

Note this is only for LVL. You'd have to refer to the NSW Framing Manual (or similar in your state) for standard timber span tables.