I will be building a deck this summer and I would like to know if any body knows how far I can canterleiver the deck over the beam. Are there any other ways to build it with different materials or posts or beams. I would like to have a 10′ to 12′ wide deck but the beam will be about 6′ frome the house. I can not go any further because of conservation issues.
Thanks,
Fooch
Replies
fooch... that's not a cantilever, that 's a seesaw..
you need a structural engineer to come up with a solution to your problem..
Mike Smith Rhode Island : Design / Build / Repair / Restore
General guidelines (i.e., conservative seat of the pants engineering) allows 1/4 the length of the joist to be cantilevered, not to exceed 3 times the joist width.
Using a 10 foot 2x8 as an example, 25% of 10 feet is 30 inches, but 3 times 7.5 inches is less than 2 feet, so the max you could lever out beyond the beam is 22.5 inches.
Much more that that and you may experiance the 'diving board' phenomenom, or as Mike described, the teeter totter effect. Neither is a good thing and won't give your party playmates a warm fuzzy feeling when they're all lined up along the rail, smiling for the camera.
There may be less conservative guidelines that allow longer cants, but 2-3 feet is about as far as you want to go. Just my opinion, though. An engineer should put a stamp on it otherwise.
WEll, Nick has got a different seat to his pants than I do and rules of thumb are only good when the thumb rules, so whose thumb are you under, besides the conservation district?
In other words, is there a local code that applies? Do you need a permit? That agency can answer for you
But to help on the practical side, you still need to know what the beam will be, and whether there is a roof over this structure, and what your local snow load is.
The seat of my pants wouldn't be sitting on it if it was cantilevered more than 24" in any part of the country. To go any further, you need very specific engineering help and it will be very expensive, comparatively speaking.
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Fooch, have your engineer think of another "beam" of sorts on the end of those joists (doubling or tripling the box). Take another framing member (post) back to and down that post at the correct angle, effectively bracing that box. Your post will have to be sized for no deflection. The outside cantelevered load will be transfered to the post. All your framing will have to be engineered to make this thing work. Am no engineer-dumb carpenter.
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2,4,6,8 why don't we triangulate? I had just the same thought.