Making a beam out of lengths of timber advice.

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Antonio-d

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Morning forum I’m looking for advice on making up a wooden beam circa 4.8m long out of lengths of timber.
Long story short I’m building a decking area at the bottom of the garden for my little boy to play on with a corrugated pitched roof on top.
I have concreted x4 6 inch square posts in the corners and want to make some beams to create a wall plate so I can add some trusses on to so I can then screw my corrugated sheets on to. I was hoping of screwing 6 4x2 together??????
I’m trying to do this the cheapest way possible may I add so any advice would be greatly appreciated.
 
So The post are in each corner
So it’s 4m x 3.6m rectangle shape I don’t really want to put another post in the middle unless I really have too.
 
3 4x2 bolted together every ft in 2 rows so 6 inch wide and 8 inch high
Im not sure thats the best configuration

4" x 12" is far better and stronger.

or if you want to keep the 150 do 6 x 2 4no

I would screw and glue it together with D4 glue -if you have lots of clamps use them too.

just to give you an idea of strength, a 90 x 315 made up of 7no 45 x 90 section has a uniform max load of 2 tonnes over 5 metres
a 56mm x 225 beam has a uniform max load of 0.5 tonne

I dont know what the deflection would be though, id guess about 15mm (1/360)

obviously you wont achieve the same strength as a glulam made in a press.
 
Im not sure thats the best configuration

4" x 12" is far better and stronger.

or if you want to keep the 150 do 6 x 2 4no

I would screw and glue it together with D4 glue -if you have lots of clamps use them too.

just to give you an idea of strength, a 90 x 315 made up of 7no 45 x 90 section has a uniform max load of 2 tonnes over 5 metres
a 56mm x 225 beam has a uniform max load of 0.5 tonne

I dont know what the deflection would be though, id guess about 15mm (1/360)

obviously you wont achieve the same strength as a glulam made in a press.

"or if you want to keep the 150 do 6 x 2 4no"
do you mean 4 6x2 side by side glued and screwed from both sides?
 
"or if you want to keep the 150 do 6 x 2 4no"
do you mean 4 6x2 side by side glued and screwed from both sides?

in glulam beams the glueline is horizontal -so the 4 pieces of 150 x 50 would be stacked on top of one another, to make a beam 150mm wide x 200mm high.

take 2 lengths of 150 x 50 and glue and screw together
then glue and screw one more to each side

the biggest issue to overcome is the fact the timber will probably be cupped -so screws will be needed say 20mm in from each edge to pull up tight.
gluing will give a more rigid beam than bolts and more appropriate for horizontal gluelines.

in construction its pretty common for builders to just use timber of say 200 x 50 and bolt together doubles or triples -obviously then you are using the stiffness of each timber so the boards have to sit upright like joists


If you were being really fancy you could glue the beam pre stressed -IE glue and screw it so it had a bow of say 12mm in it......
 
I built a deck with one level roughly that size. The built up beams to support the deck were made of 3of 2"x12" and a piece of 3/4" plywood to make it wide enough to sit in the saddles on top of the screwed in pilings. I built them in place, crown up, with glue and treated screws layer by layer. Had I built it on the ground and then tried to lift it I would have herniated everything I have. Note our construction lumber is the nominal size before drying and dressing to size. So a 2 x 12 is actually 1 1/2" x 11 1/4" when you work with it. I built it to the specs a designer drew and the building department approved. Beams are much stronger when a rectangle rather than squarish. Unless you are trying to use material you already have I would get the 6 or so 2" x 10" or 12" and build the beams. Might as well do it right rather than buckshee it and have it come down.

Pete
 
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