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apowens 04-10-2007 11:30 AM

joist span?
How far can I span 2X8 joist? for a deck will be using Trex as the decking material.

handy man88 04-10-2007 11:31 AM

1 ft.

16 inches might be acceptable if your decking was wood.

Zero Punch 04-10-2007 03:47 PM

Zero Punch 04-10-2007 03:55 PM

handy man88 FYI

handy man88 04-10-2007 04:21 PM

Apowens, check the links above and tell me what they say.

apowens 04-10-2007 04:34 PM

looks like 16 oc is the way to go. I might go with 12 oc just to have less bounce better to do more than less.

handy man88 04-10-2007 07:24 PM

Yes, 12 in oc is what I have. You're probably not going to build a gazebo, but if you plan to, you might also want to put down screen over the joists before installing the beam to prevent insects from coming through, since your gazebo, if you ever build one, would be screened also.

AtlanticWBConst. 04-10-2007 07:34 PM

Yes, Trex should be installed on joists or bridging placed 12" OC because of it's composition. It is not as rigid as wood based decking lumber.

bradley 04-10-2007 09:27 PM

joist spans
Are you asking for the span length or the oc spacing?

apowens 04-11-2007 12:57 PM

I was asking for span length but the oc info was helpful as well. All of my span lengths are less than 8' and the joist will be 12" oc due to using trex. the cantaliver will be 18". I will be using 6X6 post set on 12" footings going down 36" and 20 wide at the bottom with rebar. was going to use double 2X10 for beams but may move that up to triple 2X10. and using 2X8 as joist. also there will be a hot tub that will be sunk in the deck half way sitting on its own platform with 5 8X8 post (RR ties) one on each corner and one in the and using 2X12 beams 2X10 joist and pt 2X6 as decking so the main deck will not carry any weight of the HT. it will be a free standing deck next to the house but not attached to it. I am puting myself out there but how does this sound any issues anyone can see. its being built outside the area where permits are required is there are still some places like this. you only need one if you building a shoping mall or somthing like that is what they told me.

cibula11 04-11-2007 01:13 PM

Lowes has a deck designer that could be helpful in determining size of joists for the span you are looking for. I think that a 2x8 has a span of around 10 ft. I could be off a foot or so, but that is close. What is the size of your deck?

FYI, My current deck (which needs to be rebuilt) uses 2x8 joists 16 o.c. It is 12x16. So the joists span 10 ft or so. There is no sag in my joists but it might not be a bad idea to use 2x10 or even 2x12 especially if the deck will be spaning around 10 ft.

handy man88 04-11-2007 01:14 PM

Triple 2x10's may be overkill, and even if you go with triple 2x10's how are you going to secure it onto the 6x6 posts? Usually, 3 inches of the 6x6 is rabbetted in order to allow two 2x10's to sit on top of the post. With three 2x10's, you'll have to rabbet 4.5 inches from the 6x6 post leaving only a 1.5" flange to bolt all 3 2x10's into. It may be more sturdy vertically with 3 beams, but less stable laterally. If you insist on sturdiness, two 2x12's ma be the best on top of the 6x6 post.

Also, using rebar in the footers may be excessive, but rebar is cheap, so not a big deal.

apowens 04-11-2007 01:26 PM

I thought better to have more than needed than to have less than needed. total cost for the materials alone for this is going to be around 20K :eek: so I want to make sure it stands the test of time.

apowens 04-11-2007 01:30 PM

it is a 2 level deck total sqf 1568, twice the sqf of the house jsut about go big or stay home.:thumbup:

cibula11 04-11-2007 01:44 PM

May I ask why so big?

If you are spending that much go with larger joists. You will definately want to do it right. A little more pricey but better in the long run.

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