Adding more posts reduces permissible overhang?

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Old 06-16-17, 10:05 AM
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Adding more posts reduces permissible overhang?

I'm building a freestanding 14'x14' deck and would like have approximately 2' of joist and beam cantilever to avoid digging posts around buried utilities.

What's a little confusing is how interior posts play into the max calculation of overhang. When I review the deck construction guide: http://www.awc.org/pdf/codes-standar...Guide-1405.pdf

It's pretty clear that the max overhang is 1/4 of the beam or joist span.
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Am I reading this correctly that maximum overhang would be achieved with fewer posts spaced as far apart as possible? In other words, if I only had a total of 4 posts on each corner, I'd be maximizing my span. It seems like for every extra post you add between outside edge posts you're decreasing your beam and joist span, and thus decreasing your max overhang.
 
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Old 06-16-17, 01:07 PM
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Overhang

Are you overhanging the beams or the joists?
 
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Old 06-16-17, 03:02 PM
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I want to overhang both by 2'.
 
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Old 06-16-17, 03:02 PM
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Mears, you have it correct. Beam cantilever = Beam span / 4 (max).

See table 2 for maximum joist overhang (lesser of the 2 overhang calculations).
 
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Old 06-16-17, 07:05 PM
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So I could, say, have a 2-2x10 beam that's 12 feet long, two posts on an 8' center, cantilevered 24 inches on each side... but I couldn't have a cantilever over 18 inches on a ~15' version of that beam if I had three posts on 6' centers?

I realize the fewer posts, the bigger the lever... but still. O_o
 
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Old 06-17-17, 10:09 AM
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I'm struggling to get this to work and meet code guidelines. This is my latest attempt:
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The red 4x4 posts are from an old deck that was removed. They're directly buried in concrete and in some cases will need to be dug up. I doubt they're set very deep.

In the 4 corners I have 10' 6x6 cedar posts for a pegola. I was hoping to box the outside joists and rim board around these. The problem I'm running into is the footings for the beams are quite close to the footings for the pergola posts. Against the house, the outside dimensions of the 12" diameter circle are only like 7" apart. I'm guessing that's far too close and the holes will likely collapse on each other.

If I flip the beams the other way, I can keep the edges of the footings
for the deck and pergola separated by a foot worst case. However, I'd have bring the deck footings closer to the foundation wall (16" vs 30"). House was built in 1982 and soil is very heavy, compacted clay. Deck won't be inspected.
 
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