Deck Pier Spacing


Old 10-25-01, 12:41 PM
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I am planning to build a deck for a mobile home. Since I
cannot use a ledger board to attach the deck to the mobile
home, I plan to build a free-standing deck on concrete
piers with 4x4 dropped beam with 2x8 joist over the top.
My question is, on a 12' x 24' deck, how many beams will
I need (running the 24' width of the deck) and how many
concrete piers under each beam?

I am thinking to have 3 beams, one about 1' from each
end of the deck and one in the center of the 12' span
of the 2x8 floor joist. Or, would just a beams on each
end be enough for 12' long 2x8's??? And the piers, I was
thinking of three under each beam. Again, one about
1' from each side of the deck and one in the center where
the ends of the 12' long 4x4 beams meet to make the span
of the 24' wide deck. Or, should I have another pier
at the center of each 12' 4x4??? Or, would it be better
to use 6x6 beams???

Any help would be appreciated...
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Old 10-31-01, 01:06 AM
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I built an almost identical deck (12x18) for an almost identical situation (mobile home.) What I ended up using was two 4x6 beams (actual beams, not built up) running the length of the deck, with 12' 2x6 joists cantilevered out over each about 2 feet, if I remember correctly. This would make the actual beams about 8 feet apart. I can't remember if I used 4 or 5 4x4 posts to support the beams, I suspect 5 since I do remember that I had to center the beams over the center post to join them as an actual 18' beam was cost prohibitive. The joists were 2' on center (If I were to do this again I would make them 16" or go up to the 2x8s as you intend) and the decking was 2x6 PT lumber. This deck was very sturdy and has lasted quite well for at least the last 10-12 years.
Old 11-01-01, 04:50 AM
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I think you're all right on the 2x8's (max span is approx. 12 ft. in pine pier to pier). The 4x4's on the other hand are not substantial enough to support the span and load you're talking about. I would definitely add one more pier and use the 6x6's or make headers out of the 2x8's that you're already using for the deck, and of course you are going to sway brace the piers.

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