Sizing of beam for deck.

[jrc]

I trying to design a deck in Massachusetts.

Total size: 16' (out from house) by 18'
Joist span (ledger to beam): 14'8" with 1' 4" cantilever
Joist spacing: 12"
Load requirement: dead load 10psf, Live load 60 psf

What size beam is required? Can I use 3 posts? Are 12" piers big enough for gravel soil?

I would also appreciate advice for where to get this information. I have talked to people at building supply stores and at city hall, but they have been less than helpful.

Thanks.

[montytx]

Here is a good spot for PT wood spans ( you didnt spec which type of wood).
http://www.southernpine.com/ptdesignvalues.shtml

[jrc]

For the joists I was going to use 2x10 PT Southern Pine #2. I have a table for the joist spans. I don't have anything appropriate for beam sizing.

For the beam, I'll use whatever I have to.

[bkrahmer]

For the joists, 2x10 #2 should be fine at 12" oc. Just be sure they are #2!!! A lot of the PT lumber we get at our lumber yard is not graded #2, and will typically be #3 or standard grade. For the piers, I would suggest a product called Bigfoot. It's an inverted cone-shaped plastic thing you put into the ground which gives you more surface area and stability. If my calculations are correct, I'm thinking a 3 1/2 x 9" glulam would work for the beam, for 3 posts. If you used a glulam, you'd have to keep it sealed with a good deck stain. A 'wolmanized parallam' would be a better choice, in a similar size.

[Cole]

http://69.20.124.116/ABS2%5FBigfoot/

[Sweep]

It seems to me that for a continuous beam with two such short spans you could use multiple 2x12 P.T. lumber to make up the beam. Two would carry the load and a third would give you additonal strength for exterior exposure.

[toekneemac]

How much of a span between posts? I mean if you went every 4 feet, hypothetically, 2 x 6's would work. If you are going every 6', 2 2x10's would be fine. 8', I agree with the above mentioned, 3- 2 x 12's would be fine. Forget the laminated beams for outside. Stick with pressure treated, especially in Mass.