How much lumber to equal 6x8 beam?

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Old 06-27-16, 09:24 AM
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How much lumber to equal 6x8 beam?

Anyone know how many 2x8s and 2x10s I'd have to screw together to get the same strength as a 6x8? My guess is 3-2x8s and 2-2x10s? Can't find any actual charts with this data though.
 
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Old 06-27-16, 09:30 AM
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What's the application? The 2x10s have a different height (at least the way I'm orienting them in my mind it's the height) and that seems like it could potentially be a problem.
 
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Old 06-27-16, 09:37 AM
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Height is no issue... just wondering for a deck beam.
 
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Old 06-27-16, 10:13 AM
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Not my area of expertise but I'd think that 3-4 2x8's secured together [glued and screwed] would be just as strong as a 6x8.
 
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Old 06-27-16, 10:15 AM
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The details depend on the species of the solid beam and of the built-up beam, so you should consult a deck beam span table for exact figures. But it general, a built up beam is a little stronger than the equivalent size solid beam. But you have to compare actual, not nominal sizes.

A search for deck beam span tables should get you several useful tables.
 
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Old 06-27-16, 01:28 PM
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Yeah like I said no span tables have solid beams. They only show built beams.

When choosing a beam size are you really just going off of how far apart you want your posts?
 
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Old 06-27-16, 01:48 PM
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To some degree. Decking is generally similar in weight but if you were to put something abnormal on the deck, like a hot tub or several large planters, then more structure would be needed than the span itself dictated.
 
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Old 06-27-16, 02:02 PM
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This one has some solid beams, but just up to 4 x 8: http://www.forestryforum.com/members/donp/beamclc4.htm

Yes, you can decide how far apart you want the posts and calculate the beam size needed to support the loads with acceptable deflection, or you can work it the other way and choose the beam size and calculate the post spacing.

Benson's book on building a timber frame house has lots of tables for sawn beams if you want to chase down a copy.
 
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