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-   -   beam for pergola (http://www.diychatroom.com/f19/beam-pergola-19710/)

woodsglen 04-09-2008 05:30 PM

beam for pergola
 
Hi. I'm building a deck with a pergola over it. the deck is 24 feet and 4X6 treated posts are every 12 feet. ( 2 with one in the middle)

I was going to use 2X10 beams. but now I'm wondering if I could use 2 or 3 2X8X12's from post to post. Since I'm starting to get some twist in the posts since i put them in.. I'm guessing I may just have to box in around the posts ..or can I bolt up a beam to the post and try to "bring it back"...

Pergola Beams are SFP. they are going to support 2X8 14' span rafters 16" on Ctr with 1X4 treated strips on top to diffuse light

thanks for any "thoughts" on this one
Wayne

ncgrogan 04-10-2008 08:25 PM

If it has a roof which can catch wind, technically none of those will work and you'll need to go to a Pressure treated LVL. The moment is whats killing you with that much roof load. If there is no roof and therefore no wind load, youll should be fine with either

woodsglen 04-11-2008 06:15 AM

Thanks.. I'm thinking of 2 2x8's for "looks" and since there is only 12 feet of span with open rafters ( 2x8's) on 16 centers.

Yesterday I took 2 2X10.s screwed together at 90 degrees ( making an L beam )

I used the 2X10 on edge to provide rigidity to keep the 2x10 beam from bending.

I temporarily secured this to the twisted post and bolted it up by sandwiching the post between the 2X10 and a piece of 2X8 treated. I did not drill through the post, but rather mounted 4 bolts "around" the post like a big clamp

I cranked this down securely and ( having the whole thing resting on a pair of 2 x 8's going across the deck to the other side..) I then used basically 12 feet of serious leverage to bring the post back to straight.

and Bingo.. it went right back .. for now its lashed tow the middle post because this was just an experiment to see it the twist could even be pulled out... I can see some grain opened up on the post around the point of where the twist was/

I'm going to give it a while while i work on other things and see how it does.

I may just sandwich all of the beams on 4 corners which provides a lot more leverage and would not split the beam apart by putting pressure on the beam from within the center of the post ( with holes in the post ).

So... you think a pair of 2X8's on a 12 foot span would support 16' 2 x 8's on 16' centers??...


thanks for the input

ncgrogan 04-11-2008 07:44 PM

2x8s will work but its all a matter of the performance your looking for. Its not going to be as rigid as using (2)2x10's. I would definately go with the two 2x10's if the 2x8s are going do be sloped as the depth of the 2x8 rafter end will increase with the slope and be deeper than the 2x8

woodsglen 04-11-2008 07:55 PM

Got it!.... will do. thanks for you input, very much appreciated!

( will probably look better anyway! )


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