I am planning to build a 14' deep x 15' wide deck. The 15' length will be attached to the ledger board.

The span tables provided by the city I live in say that I should be able to get away with a beam at 12' with a 2' cantilever if I use 2"x10" joists (i.e. 12' joist span). The composite decking will be at 45 degrees so the joists 12" oc. Planning 3 2"x10" for the beam.

Am I going to have much bounce? Would I be better off with a beam at 6' and at 12' with 2"x8" joists?

Thanks,

Rob.

 

You will be fine with one beam at 12'. For a 14' deep, 15 ' wide deck, contractors or commercial deck plans like Decks USA would give you one double 2X10 beam at 12' sitting on three 4X4 posts spaced at about 6' or 6.5', and 2X8 joists. You have upgraded the joists, the beam size and the posts to 4X6. Just curious, but what type/size footings are you using?

 

Thanks for the reply.

I was going to have the beam span 6' between 12" diameter concrete piles that are 6' or 7' deep.

Code in my town requires a 3 ply beam if you want to cantilever the beam up to a maximum of 2'. Could get away with 3 2"x8" for the beam too.

Sounds like I could get away with 2"x8" joists (code in Edmonton will allow this too). When I combine the fact that I am putting the joists 12" oc I should still have a very solid (no bounce) deck. Do you agree?

Rob.

PS: deck will be 3' high.

 

Go with the 2X10's if you don't mid the extra cost and hassle of working with heavier lumber. Remember that the most inefficient way to reduce bounce is by adding more joists (12' O.C vs. 16'O.C.). This is because joist tends to spring individually, and the fact that the next one over is a little closer doesn't mean as much as you would think. Also, did you say your footings are going to be six or seven foot deep? You must be building on a hillside. How did you drill down that far?

 

Thanks for the tips. I will go with 2"x10" joists.

Yes, 6' or 7' feet. The contractors I talked to said they usually make them 8' to 10' feet but they are not paying for the concrete and said that usually 6' is enough.

The deck is not on a hillside. Here in Edmonton, Alberta, CANADA we need to go that deep to get below the frost line. I am going to get a contractor in that does piles, he has a hole auger attachment on a bobcat. I did a fence last year with a two man post hole auger and to do about 30 holes 4' deep took the whole day for 4 guys...thus I am contracting it out.

 

be sure to block the midspan of the joists.. this makes the whole deck act like one "surface" reducing individual joist sagging and bounce and most importantly.. Be sure to put the crown up when you lay your joists ..! HOpe this helps --Josh

 

Hi Josh, thanks for the tip. Would not have thought to block midspan. This would indeed give it extra horizontal stability.

Rob.