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load bearing capacity of cantilevered 2X8's

Posted by jabelone (My Page) on
Mon, Apr 30, 12 at 19:00

Does anyone know what the load bearing capacity (per sq/ft) for spruce 2X8's that cantilever 5 feet out and are nailed to the joists back 11 feet? (spaced 16 o/c). To clarify, these are 16 foot 2X8s total length but only 5 feet of which hang out in front of the house as supports for a wrap-around second story deck. I know it depends on other factors like how many nails were used to sister to the joists, but there must be a formula for an approximate range of bearing capacity under these conditions. Currently they are surfaced with yellow cedar and I would like to replace the decking with something heavier (like maybe Ipe). The framing is in good condition.

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RE: load bearing capacity of cantilevered 2X8's

Decks are assumed to weigh 10 lbs per square ft, and support a live load of 40 lbs per square ft, for minimal design standards. If the framing is in good condition, as you say, there is no reason to believe these numbers would not be applicable for your deck.

Ipe is 3 times stronger than cedar. You would replace 1.5" thick Cedar with 3/4" Ipe. The 3/4" Ipe is still stronger. Ipe 3/4" weighs 4.5 pounds per square ft. That is still much less than 10 pounds per square ft, and when you add the weight of the 2x8 framing, you're still under 10 lbs/sq ft of dead load.

Your old cedar decking weighs 3 pounds per square ft. The Ipe will increase the dead load by about 1.5 pounds/ sq ft.

Basically, the weight difference is negligible. You're good to go.

RE: load bearing capacity of cantilevered 2X8's

Thanks Aidan. That's what I figured but wanted to get some other thoughts on it.

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