Size of Beam and Post spacing?

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Old 06-19-07, 12:53 PM
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Size of Beam and Post spacing?

I am building a rectangular deck that is attached to a ledger to my home. It measures 14x26ft. The joists will be 2x10 and 14ft long. The posts will be 6x6 with a beam sitting on top of those posts to support the joists. I want to cantilever the deck by placing my beam and posts 10.5 feet from the house(so a 3.5ft overhang or cantilever). I had heard of a 25% cantilever rule which allows 25% of the 14ft to be cantilevered--this means 3.5ft should be okay. Is this true?

Also, I want to place only three 6x6 posts to support the beam. Each post would be spaced 12ft apart from any other post which would allow 1 foot overhang on each end to total the 26ft wide deck(1+12+12+1=26). The post would be inserted into the ground and fully cemented around to a depth of 48" below grade. My question is is this enough posts for support provided this is just a simple deck used only for walking and eating on(no roofs, no hot tubs, etc.) Is 12ft too far apart for post support? Also, what should I use for the beam--I was thinking about using 3 2x12's nailed together with two 1/2 inch plywood rips between each 2x12(totaling 5.5 inches wide to sit on the 6x6). Would this work? or would a LAM Beam or Steel I beam be better?

The joists would be secured to a ledger with joist hangers and blocked at 7ft(half way).


Thanks for any help you can provide.
 
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Old 06-19-07, 01:50 PM
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Size of Beam and Post spacing?

You probably will need some help for drawings to get a permit. You could also ask your local building inspector for suggestions, since you are paying him anyway.

Just because YOU do not plan for other uses someone else may. The 3.5' cantilever you quoted may not apply where you are, depending on the rest of the structure.

If you are doing an attached instead of a free-standing deck, make sure you have proper through bolts (corrosion resistant) for the PT ledger and flashing and counter flashing to prevent moisture intrusion.

Dick
 
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