cantlevered deck

Old 04-14-02, 05:03 AM
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Join Date: Sep 2000
Location: Lapeer, Mi.
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Cool cantlevered deck

Deck is cantlevered out 4'. I cut the rim joist so I can sister the the treated 2x8 to the tgi floor joist. I asked the lumber yard if a 2x8 would be adequate to support the load. Their answer must have a legal ramification as they said I would have to ask an engineer. Can't find data on line showing sizing of lumber for a cantelever deck.
Question: Is 2x8 at 16" o.c., installed according to the 3 to 1 ratio requirement, I used 16 footers so I have 12' inside and 4' outside, adequate for deck load?
Old 04-14-02, 06:16 AM
Join Date: Dec 1999
Location: South Dakota
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The reason they gave you that answer is that your not supposed to cantelever out more then 2 feet without using engineered lumber. four feet is a long way out, and without further information and a diagram, I am not sure if a 2x8 would handle it or not. My first gut feeling is a 2x10, but experience has told me to follow the mathmatics. They hold the answer. Check with you local permit department.
Old 04-14-02, 08:31 PM
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My concern is the standpoint of balance. Not knowing how the other 12' is supported.. if too much load is put on the cantilever the posts and beams can act like a fulcrum point and pivot ur deck to the ground.. its on the news every summer where a cookout or something on an overly cantilevered deck and it collapses.

However from a standpoint of rigidity its very possible. If your only concern is that the joists extend out 4' and not sag then this is my advice

Rip 1/2 cdx into 7 1/2 wide x 8' "strips" . Epoxy and galv screw these onto either side of the joist.. at the 4' end so it extends out to the rim joist and back 4' past the beam. Do this Before you put decking on. Its alot of work but a good chalk line and screw gun and youll have very strong joists.

Im not an engineer .. this is just my thought on the subject .. best to seek a professionals assistance to make sure.

Hope this helps----Josh

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