Advice

pala4058

I have 4 masonry support columns forming an area 18' x 12'. I want to span the 18' distance with 2 beams. It is then my desire to set beams on top of and perpindicular to the bottom beams, placed on 2' centers. Is it possibe and if so what size beams are required? I would like to avoid installing additional support columns as they will interfere with foot traffic.. This structure will act as a lath type cover for an outdoor living room. I believe steel would do it but I would have to mortgage my home to pay for it. Thanks

neolitic

Are you talking about a pergola, or a roofed porch?
Where are you?

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pala4058

pergola, Mesa Arizona

FramingFanatic

It really depends on what the load is expected to be. If you are putting a roof over top then that increases the load. At 18 feet I would think you might need one collumn in the center of each beam. I dont see any reason why you cant go with a built up wood beam. However i wouldnt suggest going with dimensional lumber for the beam. I would suggest using 3 possible 4 ply LVL beam. I would consult my code but i really dont feel like running outside to get ot from my truck.

hmmmm I dont think code permits a joist spacing of 2 feet oc. However that might just be up here. Although codes have many similarities from location to location. I would suggest that if your looking on saving money on materials you go with 19 3/16 inch oc. However i would suggest using a thicker floor sheathing in that case. What are you hoping to use for joists?

2x? or engineered joists?

FramingFanatic

oops i read your question as an addition. Disregard

FramingFanatic

ok well a wooden beam is entirely possible then.

neolitic

A 4X12 should work, but it might bag a little over time.
Could you put in a couple of nice knee braces?
Again, where are you?
Desert?
Swamp?
North Pole?
Gates of Hell?
Might make a difference in what materials etc.
Or are you really Dick Chaney, and can't disclose the location of the bunker?

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FramingFanatic

hmmm i would go with something beefier, and out of a harder wood. and stain it. That way you can use it as a nice architectural accent.

pala4058

Knee braces will not work in this scenario. I like the idea of staining or painting.

What size and what material for the 18' beams & 12' beams?

neolitic

Out there you could use glue-lams.
Don't have time to check right now, but 3½X16 should do for the 18's.
what ever width you want X 12" will make the 12 footers (probably 4X12 just for the looks).
In your climate, cedar would work just fine.

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FramingFanatic

I wouldnt use glulams as they will be an eyesore. I suggest using timber and your gonna want it really thick for the look. Make sure that you eye all the lumber first so that you dont get undesireable pieces.

Joe Carola

Are you talking something like this?

http://www.baldwinpergolas.com/pergo..._pergola_b.jpg

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Evan P

It really depends on what the roof will be. If it is similar to the pic. that Joe posted then a 4 X 12 will work just fine. If you are putting tile, or some other heavy load, then I would go with something a little beafier.

pala4058

Joe, the picture you attached is on the mark. I intend to keep it simple though and not so elaborate. I have 16" masonry support columns with footings and I like the look of beefy beams.
Thanks for everyones input.