A family friend wanted to know how he could put a hot tub on his deck addition. He states it would weigh about 2000 pounds full and in use, 4×5 size, I guess its one of the cheaper kinds. Does that sound like a reasonable weight for that? What would be proper framing for those loads my first thought was 2×10 on 12″ center, decking will be 2×6 to match what is already there. I’m pretty sure its off the first story and the post go down to absolute solid rock.
I tried to use some span calc I googled but honestly was a little confused with the proper way to get my answer. I was thinking of all the fancy BS I’ve ever run across I realized I never put a hot tub on a deck before or even gave it thought.
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That weight sounds reasonable. Water is about 62 pounds/cubic foot. Sounds like live load of ~100 lbs/sf. Your suggested framing and decking sounds reasonable. Other critical factors are attachment of ledger to the house, number and size of posts, methods to attach framing to posts
My thoughts are 6x6 if needed in that area, 5/8 bolts, sitting on a 2x12 girder, independent of the house, how does that sound?View Image
Framing sounds adequate and I like "independent of the house". Depending upon height above grade, a couple of diagonals to prevent racking may also be desired. Proper footings for the new posts of course.
What you're asking is a somewhat complex question. Sure, it's easy if you know how to do it, but the devil is in the details.The easy answer is ask an engineer. That way you're covered.If you don't want to do that, you need to figure out what loads you have and find a way to carry those to soil with the necessary bearing capability.6x6 posts sounds good. 5/8" bolts are fine, but I would just use two 1/2" carriage bolts per post. Do not, under any circumstances, rely on the bolts to carry the load, you must have full bearing. The only purpose of the bolts is to keep the beams on the post.If you're not attaching to the house (which from one perspective is a good thing) you need to pay even more attention to bracing. The last thing you want is for your deck to start racking. Also, you may need to shore up the posts if they are too long.2"x10" 12" OC joists will work, but that depends on the grade of lumber, the live and dead loads on a regular deck, the live loads of the hot tub, and other factors.Don't forget to make sure your footings are of proper size and reinforced if needed.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Thanks I was thinking to use 2x12 notched into 6x6 post on each side of it, bolted through it. As far as lumber your syp acq treated lumber, and the post would set on solid rock that would not be able to break up without blasting or someting. They only have a 6-10 inches of topsoil in that area. A house foundation in that area would just be drilled and pinned into it, it shouldnt be going anywhere. Thanks againView Image
That's the detail I've always used and never had a failure. What kind of girder support?
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Well my thought for the girder would be 2x12 I guess because with 2x8 I would use 2x10View Image
That is only 250 gallons of water. Has he figured the weight of the people too? I have seen calcs for these things run closer to 5000#
How large is this deck to be? The span of the joists is every bit as important a variable as the depth and spacing.
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The span out would be about 10 feet. The 2000 lb. would come from the paperwork he got with the unit, best as he could recall. I dont think it would be possible to fit more than 2 people in it I was thinking maybe 2500 max, if the paperwork didnt include people in it.
Guessing to use 6x6 posts in the immedate area like say a 6 ft. wide area framed with real beefy for the tub to set on and frame the rest of the deck like normal. Set on a 2x12 grider with 5/8 bolts through.
I havent been attaching decks to the house in the last couple of years because I can save the trouble of flasing.View Image
well, three thousand pounds on an area 10x10 is only 30#/sf for engineering.Try 4x12 or 6x12 for girder though, not 2x12
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Are you saying 2x12 on each side of a 6x6 post isnt enough? View Image
I thought you were saying a single 2by.I would also notch into the post. Relying only on bolts has never appealed to me. That places all the bearing on a tiny area the size of the bolts
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Thanks, anything Ive done where I get to decide Ill notch the post for the girder and use one size bigger than the joist size. I guess he's redesigning the thing as we speak, so who knows I think he wants to go 16' out. It shouldnt change what I was thinking to do in the hot tub area because the joists will be 12" oc and the girgers would be about 8' apart, 2 notched into a 6x6.
The way its going already I might not even get involved but I sure love to have the extra work, ya gotta take it when ya can find it.View Image
To it sounds like a good time to tell the person he needs a engineer. Unless you want gamble your life savings.
I understand that engineers have their place, but I don't think this is one of those situations. He asked because he wanted to know what was feasible and reasonable, I asked here to get a trusted second opinion. You should understand that if I just said go get an engineer it wouldn't happen, he isn't going to sue me, and I think its something that is fairly common to do, just looking for good advice.
I would never do anything that I didn't think was proper. Ok sure the manufacturer says 2000 so figure it for 4000 and then you should have it covered, I don't think an engineer is required for that. I just thought if someone here had done something similar they could pass it on, I've found enough good info on here that I trust the reasonable answers.View Image
This house we bought last year came with a big hot tub out
back.
Four hundred gallons (seats six). the previous homeowner built the
deck. I haven't crawled under there, but judging by his other
creations it's nothing fancy.
2x6 construction I know. Ten foot square, 16" centers.
Vague I know but I'm not crawling under there.
Anyhow it doesn't have to be too massive to hold it up.