Wooden i-beams

[bigegg]

Does anyone know anything about wooden "engineered" i-joists?

Im in the process of (yet again) rebuilding my workshop.

I have a need for a couple or more 16ft beams, and a wooden "I-beam" would seem to be perfect for the job.
Basically a top and bottom rail (flange?)of 3x2, and a "web" of 12mm OSB.

But: the longest 3x2 I can get hold of is 12ft.
(And 2x8ft pieces is cheaper).
Is it just a matter of butt jointing the rails end to end, but staggered from the joints in the OSB?

I'm basically thinking two 8ft pieces end to end on the top, and bottom, then a 4ft piece of OSB, then a 8ft, then another 4ft, in the "web" to make a 16ft beam.

I've watched umpteen videos, and lots of websites, but can't find any decent pictures of how the extra long beams are made.


I did find a few designs where the top and bottom rails seemed to be made of 3 layers of 18mm ply, rather than solid timber, which is an option, I suppose.

 

[Brad93]

I think a steel beam would be much better than wood over that span.

 

[bigegg]

I think a steel beam would be much better than wood over that span.

Undoubtedly -
but:
I have the timber.
I might need five or six of them - and the cost would be significant, even if I could source them second hand.
Wooden beams would let me tailor the width/depth to match the design, rather than the opposite. (Basically, I could slope the roof by altering the heights of the beams)

Looking at spec. tables for commercial I-beams, they are more than strong enough for what I want - and much lighter.
(Which is also important, since I'll likely be working alone to fit them).

 

[bigegg]

I'm basically building a 4.8m square open span room, framed with 3x2s.
Steel clad on outside, OSB on inside with insulation in the gap.
I have around 2ft of height from the "ceiling" to the highest point for "permitted development (within 2m of boundary), so I'm investigating various designs for the roof - either a pent, or single slope.

 

[sako243]

But: the longest 3x2 I can get hold of is 12ft.

Really?! Everywhere around here sells it in 4.8m lengths (16ft as near). Quite a lot will be able to supply up to 6m lengths off the shelf too. I presume you're trying proper timber merchants rather than the likes of B&Q etc?

I guess I'm lucky in that I can get the local sawmill to cut me 12x4s etc., up to 6m within a few days

I've gone overkill on the joists in my workshop (office above) and put in 12x2s. Technically an 8x3 is enough for a 4.8m span in normal domestic loading I seem to recall.

 

[mtt.tr]

I would find a generic calculator online then copy what it says.

 

[bigegg]

Really?! Everywhere around here sells it in 4.8m lengths (16ft as near). Quite a lot will be able to supply up to 6m lengths off the shelf too. I presume you're trying proper timber merchants rather than the likes of B&Q etc?

I guess I'm lucky in that I can get the local sawmill to cut me 12x4s etc., up to 6m within a few days

I've gone overkill on the joists in my workshop (office above) and put in 12x2s. Technically an 8x3 is enough for a 4.8m span in normal domestic loading I seem to recall.

I'll double check tomorrow - it depends on the premium for the longer lengths.
The 12ft ones are £6 a length, and pressure treated.
(Although I'm quite clumsy, and may end up accidentally spilling creosote all over whatever I end up with).

 

[addjunkie]

Any builders merchant will sell you 4.8m c16 or c24, and get you longer if required

 

[bigegg]

I would find a generic calculator online then copy what it says.

I did...
But:
I still don't know if/how I can joint the timber which is used for the rails/flanges

 

[bigegg]

Any builders merchant will sell you 4.8m c16 or c24, and get you longer if required

Just checked at selco - and so they do.
£11 a length, and free delivery.

I think that might be a winner.


But:

I'd still like an answer to my original question...
Just for the sake of appeasing my curiosity.

 

[sako243]

The 4.8m stuff is usually cheaper than the shorter stuff although given I've got an account it's usually just the same rate.

Volume drops the price as they normally just charge by the metre.

 

[bigegg]

The 4.8m stuff is usually cheaper than the shorter stuff although given I've got an account it's usually just the same rate.

Volume drops the price as they normally just charge by the metre.

It's about +50% over the price of 2x 2.4m lengths

 

[sako243]

Something isn't adding up then. Definitely cheaper buying the longer lengths here, to be honest they don't normally stock the smaller ones.

 

[bigegg]

Something isn't adding up then. Definitely cheaper buying the longer lengths here, to be honest they don't normally stock the smaller ones.

I have another couple of timber merchants I can check.
Selco is the only one I can get a price from tonight.
And the "free delivery" is definitely a factor - cos 4.8m isn't going to fit in my car, or on my trailer.

 

[TEO]

I have another couple of timber merchants I can check.
Selco is the only one I can get a price from tonight.
And the "free delivery" is definitely a factor - cos 4.8m isn't going to fit in my car, or on my trailer.

I think the joint you're looking for is a "scarf" joint, lots of different types, some fantastically complex demanding extreme accuracy with hand tools that haven't really changed much since the middle ages. Staggering the skill level involved in medieval framing.
However, much as I like the idea of doing it yourself, I don't think scarfing will be suitable for your purpose - not unless you've done the time under some master learning how to do it right. Might as well spend the time earning the sponds to buy the right length..... If only I'd ever followed my own advice, good luck.

 

[bigegg]

I think the joint you're looking for is a "scarf" joint, lots of different types, some fantastically complex demanding extreme accuracy with hand tools that haven't really changed much since the middle ages. Staggering the skill level involved in medieval framing.
However, much as I like the idea of doing it yourself, I don't think scarfing will be suitable for your purpose - not unless you've done the time under some master learning how to do it right. Might as well spend the time earning the sponds to buy the right length..... If only I'd ever followed my own advice, good luck.

I know several different ways to scarf joint.
But is that how it's done in a factory?
There must be some industry method, given that i-joists are available up to (at least) 30ft long.

Ps: I'm retired, my days of going out to earn are done with.
I like to make stuff for myself now, rather than make money.

 

[Farside]

I have a need for a couple or more 16ft beams, and a wooden "I-beam" would seem to be perfect for the job.
Basically a top and bottom rail (flange?)of 3x2, and a "web" of 12mm OSB.

I made my own.
5m long 2x8" and paired up with 2x2 on the bottoms.
Supported in joist hangers at one end and resting/bolted/nailed to the top of the dividing wall at the other.
The 2x2s were glued and screwed every foot or less.
The end result was a ceiling with no sag and when I laid the floor upstairs there's no bounce at all. The addition of the 3/4" ply flooring made the whole thing rock solid.

 

[TEO]

I know several different ways to scarf joint.
But is that how it's done in a factory?
There must be some industry method, given that i-joists are available up to (at least) 30ft long.

Ps: I'm retired, my days of going out to earn are done with.
I like to make stuff for myself now, rather than make money.

I don't think the factory made finnjoists have any joints. I suppose the web might be in many parts depending on the total length but given that 6m + lengths of graded timber are readily available I shouldn't think there's any need for joints top & bottom.
I've used glulam beams but don't think that's what you want.
Some of the engineered boards & components have finger joints, Is that the one you're looking for finger joint spindle moulder cutter?

 

[bigegg]

I don't think the factory made finnjoists have any joints. I suppose the web might be in many parts depending on the total length but given that 6m + lengths of graded timber are readily available I shouldn't think there's any need for joints top & bottom.
I've used glulam beams but don't think that's what you want.
Some of the engineered boards & components have finger joints, Is that the one you're looking for finger joint spindle moulder cutter?

Finger joints seem like a reasonable way of doing it for mass production.

ill take that as my answer, then I'll be able to sleep tonight, with my question answered.

i do have a router bit that will cut them: don't fancy cutting the end of an 8ft 3x2 with it though: not on the router table. And DEFINITELY not freehand.
it would even be difficult to do on the RAS.

if I *must* do it, I'll cut a regular angled scarf, with a mending plate/loose tenon reinforcement.

 

[gaz1]

this will give you what you need

but note even the osb is glued and joined to each other as one piece

and on some they are double the thickness on top as well as bottom all parts are glued

you want to be using finger joints on all your wood beam building