Deck plans - joist and beam sizing

BJohnston

Hey guys,

In the beginning stages of planning a deck/paver project for the spring. Right now, I’m trying to get my deck plans straightened out.

*The dimensions will be roughly 16x12 built from #2 PT pine. 16’ (length) will be secured to house
*The deck will be attached to the house via ledger board.
*Footings will be concrete piers approx 36-48” deep. I’d like to keep these 5’ or 6’ o/c as our local code requires any footing within 5’ of foundation to be 8’ deep (and I don’t want to dig 8’ down in clay)

The questions I have are around lumber dimensions. I plan on going 12” o/c with the joists.

1. Can I use 2x8 lumber for all this? Or do I need to step up to 2x10?
2. I read on decks.com that if I have post spacing 6’ and a joist span of 12’ then I can use 2 2x8. What does this mean? Do I sister (2) 2x8s? or one on either side of the post on top of the footings?
3. I’m assuming joists should run perpendicular to the house & ledger board. Or should they run parallel?
4. Do I need footings underneath the deck or only the perimeter?

Thanks guys, hopefully with these few questions answered I can put pen to paper and finalize the plans to submit for permit.

jagans

First of all your statement re 5-6 feet on center makes no sense. Your local code want you to go down to virgin soil, and that is probably why you have to go that deep if you are 5-6 feet of your foundation.

You dont say what kind of live load you are planning on putting on your deck, so how can anyone say what you need?

Ledger strip? I through bolted a 2 x 10 plate to my rim joist with 5/8 HD Galvanized Bolts with large flat washers inside and out, 16 inches on center. I used Simpson hangers and 2 x 10 joists 16 inches on center to span 12 feet with a two foot cantilever over a triple 2 x 12. Mine was rated at 100 lb live load.

You have to do the math, my friend.

__________________
" A lot of men build things, and a lot of things fall down "

Daniel Holzman

Usually the town you live in will specify the code you need to design to. If there is no code, you can safely design to the International Residential Code prescriptive design guide for decks. Here is the link:
http://www.awc.org/publications/dca/dca6/dca6.pdf

Everything you need to know about sizing structural elements, connections, footers, railings etc. are in this manual.