Stuck with steel sizing

[angelboy]

The beam has come in at £126 each so more than double what it would cost for three 2x9s.

Choice made I think, thanks for the input, I've saved a fair few quid and lots of time!!!

 

[tony1851]

My invoice is in the post

 

[noseall]

Right. If I make sure the middle one has grains in the opposite direction shouldn't it be even stronger?

You can try and crown them in opposite directions to give a bit of pre-stress. Tricky with a three ply though.

We've done with a double before. Fix one end. Pull the beams parallel then fix the middle, then pull the other end and fix that. They do require a bit of effort regards mauling and clamping and also are reluctant to be pulled up tight together due to the wood wanting to twist slightly as it is trying to distort across its width.

 

[^woody^]

Don't forget not to bolt (or coach screw) along the centre line, but 1/3 from the top and bottom and alternate - every 500mm should be OK.