Decks, Patios, Porches and Docks - Deck to support a 8x8 hot tub

I am in the process of finishing plans for my 32' x 16' deck. The 32' will be attached to the house. Ledger and all the joists will be 2"x10". I have planned on a beams at 7' and at 14' of 3(2"x12"). The posts will be 6"x6" located at 1',11',21',31' leaving 1' overhang of the post. I will have my building department determine the diamiter of the concrete footings, I do know that in CT the must be minimum 42' down. Decking will be 2"x6" running perpendicular to the joists. All will be SYP.

The hot tub with water and people will be no more than 6400 lbs. I was wondering if the two beams would be enough support. I was thinking of a third beam at the 10' 6" mark (basically spliting the difference between the two other beams. I was planning on running this third beam for 12'. from the outside edge to 1' past the second post. That leaves three beams 3(2"x12") with 6"x6" posts at 1' and 11'. Do I need to put another 6"x6" post on each beam splitting that 10' spacing? That would give me three beams 3(2"x12") beams 12' long and 7' apart with each beam supported by 3 6"x6" posts at the 1', 6' 11' marks.

Any help would be greatly appreciated.

Ron

The 6400 pounds (100 psf) sounds more like a guess than a real concentrated design load. Make sure you consider the equipment weight,water weight, person weight and the posiblities. - Like 10 people sitting on the snow covered cover of a filled tub, etc.

One other thing to consider is the deflection (a people "feel ggod item") that exists beyond the simple structural design.

Often a separate support for the tub is a viable option from a construction and cost standpoint.

Dick

Dick,

Thanks for the quick reply. The 6400 lbs was derived from the maufactures filled tub weight of 4,858 lbs, to which I added 7 people at 200 lbs for another 1400 lbs. That gives a total of 6,258 lbs. I rounded up to 6400 to make the math easy.

You mentioned "deflection" and I think that means the up/down movement of the deck when you walkl on it. I was thinking that with a beam at 7' and the beam at 14' the 2"x10" joist would only be spaning 7' maximum. I hoped that that would cure the deflection issue.

As for the area under the hot tub, That is where I thought that a thired beam (again 3 2"x12") in the middle of the 7' span between the two other beams would give enough support. So the hot tub would rest across all three beams. I needed to know also about the footings. I think that to be safe I will need to put 3 (1',6',11') under each of the three beams for the 12' area under the hot tub. I hope that makes sense!

I should add that the deck surface will be no more than 3' above grade!

Thanks again for any additional info and suggestions.

Ron

With the extra beams, posts and footings, you should be in good shape as long as your joists are no more than 24" O.C.

I think you have sufficient structure without adding the third beam, but I would add the middle post on each of the other beams, to reduce the 10' span. That is assuming that the hot tub is roughly center over the two beams.

Since you mentioned your building department would size the piers, you must be pulling a permit for this construction, which means they will also be reviewing the structure and sizing of the components. Tell them you plan to put a hot tub on the structure and let them tell you if you have enough support.

In my county, I can talk to one of the building department's engineers, who won't be the least bit shy if I haven't designed something strong enough. Maybe you can too. In the end, they will be the ones to approve/disapprove your plans.

Ubob,

I'm in a building dept. at LEAST once a week picking their brains. I want to know what they will or won't approve BEFORE I build it. Different jurisdictions require diffeernt things, and they all have their little idiosyncracies (now how's that for a word??) It's a WHOLE lot cheaper to change the plans on paper than it is to change the WOOD once it's in place!!

Lefty: When I said they would be reviewing his structure, I meant his plans for that structure. I don't know about his/your area, but before my local guys give me a permit, they want to see architectural drawings of what I have in mind. For a deck, I need to give them a floor plan, a plat drawing of my lot showing utilities and easements (and the proposed deck), details of the ledger/beam/joists, details of the railings, details of any stairs, and have the materials called out on all of them.

Certainly, after he gets the permit and builds the deck, someone from his building department should inspect/approve it as well.

I wouldn't recommend to anyone that they build something, then ask if it's "OK" - I hope it didn't sound like that's what I was suggesting. Thanks for bringing that up.

Ubob,

That's EXACTLY how it has to be done. You design the deck, put the design on paper, submit the paper to the bldg. dept., let them make their changes -- and THEN go build it! Like I've always said, it's easy to make changes on a piece of paper. It's tough and expensive to make the changes in wood once it's built.

newdivision,

Certainly you'll get an inspection of the deck after it's built. Follow the approved plans and you'll have no problems. Most bldg. depts. have standard handouts that show the framing details, the stair and railing requirements, etc. As long as you use those handouts as the MINIMUM, and beef things up from there to support the hot tub, you will be fine.