Do I need a double Joist...??

by RC
(Montreal)

I'm building a 17' x 17' deck using deck blocks which is at ground level. The trusses & joists are 2x6s. Based on advice given from someone at HomeDepot I was told to double up the joists for the 2 main trusses running the length of the deck.

Is this necessary or overkill?? The deck blocks are spaced approx. 4' 2" going East-West and approx. 5' 7" apart going North-South.

Your advice is much appreciated.

Renato.

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Jun 10, 2008
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Joist Size and Spans With Deck Blocks
by: Editor - Rich Bergman

Using double 2x6 joists will certainly increase the span length of the joists between deck blocks. However it is unclear from your question if you mean to double up all the joists or only some of them.

I can't really answer your question until I known the configuration of the joists.

But I will try. If you beams in the deck blocks set at 4' 2" spacings, the 2x6 joists will have to span the 5'7" distance to the next beam. This is a fairly long distance for a 2x6. Doubling up 2x6s in this case would be helpful as you may find the deck will bounce too much.

On the other hand, if you run the beams in the deck blocks set at 5'7" spacings teh 2x6 joists will only span 4'2" between beams. This is more manageable. If you would to double up one or more of these joists it would offer extra strength in the area close to that joist but not over the entire deck.

Hope this helps you out.

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