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beam design

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Jun 23, 2013, 03:55 AM
beam design
I am building a 30 x 50 single story pier and beam home in central Texas.
I have drilled 35 piers in a 7 by 5 fashion meaning 7 across the back and 5 down the sides
. The beams are running lengthwise from left to right.They are a max of 8' apart. I was wondering if a beam consisting of 2 2x8's sandwiched with 1/2 ply in the middle would suffice since they are spanning a max of 8' . The beams are 7 1/2 feet apart from each other with 2x8 floor joist on 16 center

This message has been edited. Last edited by: shanetill254,
Jun 23, 2013, 10:04 AM
You may need to do some local engineering or code inquiries to get a 100% accurate answer for this but some general facts to consider:

1. Usually, an 8' span of a beam will require at least a double 2x10, often a double or triple 2x12. However, this would be for a more typical center line beam construction where the joist-to-beam span is more like 12'. In your plan, you are increasing the beam count so this will help spread the load.
2. The addition of 1/2" plywood serves the dual purpose of adding strength and also making the sandwich total 3-1/2" in width. This is important for headers, not so much for beams. Instead of adding the plywood, it's more common to add in a third 2x piece.
3. I would strongly recommend going to a truss manufacturer and let them quote you this in floor trusses. Odds are that trusses will be cheaper to buy, MUCH easier to install and will give a more consistent level. The only downside is that the trusses will be taller than your planned for 7-3/8". A big plus though is that they will do all the engineering calculations to guarantee you are sized correctly for the load.
4. Just like trusses, take a look at I-joists. The same advantages hold true plus you get the I-joist computer to calculate all the loads.