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billybarty 07-04-2012 08:11 PM

beam span when laminated
 
Looking at wood beam span tables for a deck i can go roughly 14' between posts when the posts are 8' high and the deck is made up of 3-2x12 laminated together. Can anyone tell me how much further I can go between posts if I laminate in 2 pieces of 3/4 inch treated plywood between the 2x12?

hand drive 07-04-2012 08:17 PM

you would be better setting a quad instead of plywood in the beam, plywood has breaks every 8' so would lessen strength considerably at the breaks.

billybarty 07-04-2012 08:25 PM

I don't have any spans on tables I have found on the net for a 4x beam. I need to go 16' on one side of the center post and 23' on the other side. Will a 4x beam handle that?

joecaption 07-04-2012 08:44 PM

A 4 X beam will sag, twist and check.
Plywood would also rot with the end grains laft exposted between 2 X's.
Far better to just add more supports to shorten up the spans.

robertcdf 07-04-2012 08:53 PM

Go steel or a glulam beam

Joe Carola 07-04-2012 08:54 PM

Have an architect or engineer spec a treated glulam.

benjamincall 07-04-2012 11:15 PM

These links might be of use:

http://www.johnbridge.com/vbulletin/deflecto.pl

http://www.woodbywy.com/services/s_forte.aspx

http://www.hsh.k12.nf.ca/technology/...e_11/index.htm

You can use the Forte software (free from Weyerhaeuser) for more than just I-joists.

hand drive 07-05-2012 07:02 AM

Quote:

Originally Posted by billybarty (Post 958089)
I don't have any spans on tables I have found on the net for a 4x beam. I need to go 16' on one side of the center post and 23' on the other side. Will a 4x beam handle that?


23' is a long way to span with regular 2x lumber. you would need an engineered beam for that span along with a qualified engineer to recommend the beam sizing. if possible, a post for each mid span from center looks like the way to go...


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