make your own glue lam. Two 2x's with a 1/2" OSB sandwiched in the middle. Liquid nail and thru bolts every 6 or 8 feet.

That will span farther than a single 2x (of whichever depth you choose from a span chart) but I wouldn't trust it to actually go twice as far.

#2 grade, 16" OC, 40/10/360 chart gives you:
2x6 - 9'-4"
2x8 - 11'-10"
2x10 - 14'-0"

So if you're building a beam/girder out of 2 2x's and 1/2" OSB, it will go farther than that, but the info for how much farther is not readily available and would require a structural engineer.

I would use a half lap joint to join the beam lengths directly over the post. With that said a single 4x6 is pretty puny as a deck support. You are spanning 23 feet; if your joist length is 6 feet, you need a support post every 6'2". As the joists get longer, the spacing for support posts gets closer together. A double 2x12 will span a greater distance between support posts. Another option is to use double 4x6's stacked on edge to get additional support. My suggestion is to sketch it out and take it to an engineer. If you need a permit your permitting office is going to know the minimums.

I would also reconsider the post dimensions. Here in Florida we use pressure treated southern yellow pine to resist moisture and bugs. We have built a lot of decks and buildings over the years and I won't use anything less than a 6x6 post based on experience with twisting and deterioration of 4x lumber. I hate looking at crooked posts.

Check out the chart here for useful information on spans for dimensional lumber for decks

http://www.decks.com/how-to/40/beam-span-chart-table

Good luck with your project

quote:

Originally posted by SapperSteel:

quote:

Originally posted by wrightd:
. . .Any advice appreciated. Arc ?

You've been using the term "beam". I think what you really mean is "joist". But maybe not. What rests on the top surface of your "beam"? Is it your deck boards (in which case we're really talking about joists), or is it the bottom of joists that cross it at a 90 degree angle (in which case it really is a beam)? Or, are you using saddles to hang your joists off the side of your beam?

Word "pictures" are hard to convey. A sketch would be really useful.

To give you any useful advice on member sizes for your deck, I need to know:

-- What is the spacing of your joists center-to-center?

-- What dimension lumber are you using for your deck?

-- What kind of lumber, ie: what species of wood? For example: white pine, Idaho pine, oak, or something else? The different species have significantly different maximum flexural and compressive and shear stress values.

-- What loads do you plan to put on your deck?

-- How do you plan to fasten all the members together?

Hi Sap.

To answer your questions specifically with a simpler word picture, this is my latest thinking:

The header will be attached to the side of the house. Size of this header board TBD, but it will be a 2x something pressure treated pine, typically sold in the southeastern US, as will all the wood for this deck.

The 2x something 8 ft joists will be attched to the header at 90 degree right angles via conventional joist hangers. I'm assuming the depth of the joists will be the same as the header, whatever they turn out to be. Approx. 7 ft out from the header, the bottom of the joists will sit on top of the beam, again at 90 deg right angles, tied in with hurricane ties, and blocked appropriately to prevent rolling or tipping over to keep vertical rigidity. I'm thinking conventional 16-inch on center spacing for the joists. Since the joists are 8 ft long, and the beam 7 ft from the header, approx 12 inches of the joists will overhang the beam, to help visually cover the beam and its bases.

The beam will be parallel with the header board 7 ft out from the house, and will be mounted to G185 galvy adjustable post bases with a built-in standoff, with each base in turn bolted to poured concrete sonotubes.

The rest of the joist, 1 foot remaining after it crosses the beam, will be overhang, to help visually cover the concrete sonotubes.

The deck boards will be conventional pressure treated 5/4 x 6 in pine deck boards. Total lengh of the deck boards, running parallel to the house and at right angles to the joists, is 23 ft. So the actual size of the deck will be a rectangle 8x23 ft. I would have gone 24 ft, but the side of the house isn't quite long enough on that end to accomodate 24 ft without being visually distracting.

I wil fasten all of these parts together with the correct and recommended G185 spec galvanized connectors by Simpson Stong-tie, shown in their "Deck Connection and Fastening Guide" printed publication.

I'm thinking the standard 40 psf live deck load rating will be sufficient for design purposes, since the deck will hold mainly my wife's potted plants and small decorative trees, a small round deck table with two chairs, a bbq grill, that sort of thing. If we have people over, they won't all be standing on the deck, etc., they'll be in the pool or the kitchen. But if there's any question, I'd rather overbuild slightly since it's probably not going to significantly impact total expense either way.

So for all this, I need to know the sizes of the header, joists, beam, and the distance between each poured concrete sonotube. The height of the sonotube concrete pillars will determined by the total height of the deck minus the sum of the height dimensions of the beam, the joists, and the galvy shoe standoff.

I will not be mounting the beam on any pressure treated 6x6 posts, since the deck is very low to the ground, the idea being that the combined height of the poured sonotube footings, the beam, and the joists, will give me more than enough height to achieve the desired low to the ground profile.

So based on these ideas, which I'm not married to based on my lack of knowledge in this area, it seems like I can complete these plans with the following unknown information:

Size of header - 2x8, 2x10, etc. ?

Size of joists - 2x8, 2x10, etc. ?

Should header be same height as the joists ? ie, 2x8 joists mounted to 2x8 header with joist hangers. Is that usually the case ?

Size of beam - 4x whatever, 6x whatever, etc. Solid sawn pressure treated lumber, or should I build the beam myself ? And how ? I'm assuming it will need to fill the width of the galvy shoe perfectly, but I don't know if this is necessarily always required. I've not seen any pictures suggesting otherwise.

Given the above unknown sizes of framing lumber, I need to know how far apart the concrete pilllars be that are supporting the beam.

IF I can figure out these critical dimensions, then it seems like basic math and rough pencil drawing should get the job done. I just don't have enough knowledge to figure these things out.