I thought the 4x6 was stronger. This will be a new deck (extension). The HO currently has the hot tub (filled & in use daily) sitting on an existing 10' W x 20' L deck, span is 8' (12" overhang front/back) with 2x6 joists sitting on top a double 2x6 beam and no center support, 5 - 4x4 post spaced 5' on front and back. I was amazed it had not collasped when I first saw it. HO want's to add a 5' x 15' extension to move the hot tub out farther. No problem building the new to meet/exceed the requirements, I was just wondering if there was any real difference between two 2x6 or one 4x6 other then dimensionally. I've used both and know there is post beam/tie caps available for each.Bob Kovacs said:A 4x6 will be stronger, as it's actual dimensions are 3 1/2 x 5 1/2. two 2x6's would total 3 x 5 1/2, which is approximately 15% less cross-sectional area.
However, if you're talking about supporting a hot tub, you'd better get far more design info than this to work with- 6" deep anything won't span very far supporting a hot tub.........
RobertCDF said:You can use 2x6 for the joists if you like... but then I would put a beam every 2' under the joists... Other wise I would recomend double 2x10 at 12" O.C. and some large beam just depending upon what distance you want between the posts. But then again I just overbuild most everything.
Lol it might be cheaper... you would just have to run the numbers.... or you could just put the tub on a slab and be done with it. Then build the deck around it. Personally I think this looks better.old27 said:Robert-
I'm with you all the way on the beefier framing call........or he could use 2x4 for the joists...and then put a beam every 1' under the joists.
RobertCDF said:Lol it might be cheaper... you would just have to run the numbers.... or you could just put the tub on a slab and be done with it. Then build the deck around it. Personally I think this looks better.
Like most things, it's not quite that simple. A 4x6 joist is theoretically stronger than a doubled 2x6 joist because it's 1/2" thicker, but the actual strength depends upon the knots and other inherent weaknesses of any particular piece of lumber (#2 lumber can have some nasty spike knots or large not-so-tight round knots or wane).ATHC said:I thought the 4x6 was stronger.
Thanks for all the input from everyone. Robert, your thinking was inline with what I was wondering. Both ways have their purpose, however there's numerous factors that can alter both outcomes.Riversong said:(I'm assuming the new deck will also have an 8' span).
If you want to be sure there won't be problems, then going 12" oc won't be a bad idea for the area carrying the hot tub. And make sure your pier footings can handle the extra load, too (use bigfoot pier bases).