Best way to do end to end joints in 4 x 2 ? In other words to make 2 x
2.4's into a 4.8 ish length.I was thinking either lap joint & glue & bolts or those spiky washer things - joint doesn't have to be in line, just resist deflection. Timber on edge.
Any thoughts?
Umm....
Buy a 5.4m length and cut it down?
What's the application? Will the joint be on show?
Twas just an example! I need to join to get to 9+ metres.
Bearer for deck - never be seen - ugly no problem!
A scarf joint sounds appropriate, using plenty of glue and a few nuts 'n' bolts. You will lose a bit of length though, because of the overlap. It was good enough lots of years ago for extending telegraph poles, and there's a fair bit of stress on them...
I assume that the cross sectional dimensions would be more as well :-)
I would have thought something like bracing pieces of (say) 1m bolted through with long coach bolts and the pieces glued with PU glue. Plane off the treated area for the glued faces.
Fancy would be one of the many variations in scarph joints, but these often need to be hand cut and take practice.
Assuming you're using the timber as an edge beam, a long vertical lap- joint with lots of bolts and big washers is probably the simpler solution
On Tue, 03 Jul 2007 23:50:50 +0100, Frank Erskine mused:
Scarf joint was my first thought. I assume this bearer is going to have intermediate support though?
In this case no. 4 x 2 is the only size that will fit under the door thresholds, so extra supports will be used.
That was my first thought - telgraph poles? Good enough for them...............
Oh yes! Many!
lap and timber connectors would work and probably be more than adequate for a deck.
Alternatively a longish scarf joint, with bolts through the verticals. (Same technique as can be used to extend a ridge beam in a roof).
You can either do the simple one with a 1 in 8 to 1 in 10 slope on the timber, glued up and bolts either vertical (or drilled at an angle so as to be perpendicular to the scarf).
(counter sink the nut and bolt if you want a flat profile):
B B
---------------------------------- / / /
--------/------------------------- B B
(bolts at B)
The stronger one, uses a profile like: ________________________________ \ / / / ________ \_____________________
The sloped cut is the same, but does a 90 degree turn a little way in from each edge on top and bottom. Once glued and bolted this is better at transferring the bending moment into compressive forces on the top of the joist, and reduces the shear loading on the glue line.
The first is easy to cut on a SCMS, the latter requires a stopped cut so is best done with a handsaw or a decent jigsaw. (you cut it in three goes - the slope from one side to the change in direction at the other edge, then the cut from the far edge to meet the slope, and finally trim off the sharp point).
Drill two 12" holes down each piece and Araldite two pieces of 24" D12 reinforcing steel into the holes.
Place a short piece, say 1metre, alongside the two that you want to join so that it overlaps the joint by 0.5 metre each side and then glue and screw the short piece to the two long pieces. OK, at the joint area you will have a piece of wood that is 4" x 4". Plenty of PVA glue over the joint area before you screw the lot together. When that sets you can even back the screws out and then try and break the joint by jumping on it.
Chris.
Your drilling would need to be so accurate that I'd rule it out for an on-site situation
Just lap them above a support. No need for any extra glue if they are not load bearing in any way. If you are worried that the screws will not be in-line then butt them and screw a strip either side.
Have you thought about using a 3.5m long nail?
:)
Doh! Why didn't I think of that? Do Screwfix do them?
Nope but they have a subsidiary company...try
LOL!
Which begs the question. Well I think it does anyway. What size hammer would be needed to belt in a 2.5m long nail. I am guessing that the hammer head would need to be about the same size as row of five 3 story terraced houses. But this is obviously not based on scientific analysis.
Arthur
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