Will deck support hot tub


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Old 05-31-14, 06:17 PM
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Will deck support hot tub

I recently bought a hot tub it is 7'x7' and says it will weigh 5800 full (i'm sure this is slightly over exaggerated) It is 375 gallons. My main plan is to put it on my wooden deck. The deck is built only a few inches above the ground, there is a span of 16" between each 2x6 or 2x8 that support the planks. I haven't taken any planks up, but I would believe that the beams would be on some type of concrete footing. Do you think it would support my hot tub?
 
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Old 05-31-14, 06:26 PM
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I pulled a board up, they are 2x6 and I couldn't see any supports where I pulled it up at.
 
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Old 06-01-14, 06:13 AM
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In general I would say a normal deck will not safely support a hot tub. While the size of the joists is important you also need to look at their span (the 16" you mentioned is not the span, it is the joist spacing). Since you could not see any beams or supports underneath when you pulled a board that is also not a good sign. You also need to have the posts/columns to carry the load down to the ground and the footers so distribute the load into the soil.

Most spa manufacturers provide instructions for suitable bases. I'm guessing you will need to build a support structure into your deck to support the weight of the spa. The existing deck not under the spa can remain but the spa itself will need special support.
 
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Old 06-01-14, 06:26 AM
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Thanks for the reply, the span of the deck is only 8'. If I take the boards up I could easily add bracing to the existing deck, it is only built a few inches over the ground. What I was thinking was doubling up the 2x6 around the perimeter of where the hot tub will sit and add some concrete block underneath the 2x6 beams for support. Do you think this would work?

I do have a concrete pad where I can put it, but that is not where I would like it to be permanently.
 
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Old 06-01-14, 11:32 AM
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It's not so much beefing up the span, but to give vertical support via footings and post/beams. I know you are limited on space, but it will sag if you don't address "vertical".
 
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Old 06-01-14, 11:07 PM
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If your vertical clearance allows it, you could install some stout timber members (at least 4' longer than the hot tub's length, centered) perpendicular to the joists under the deck, spacing them at 12" centers and supporting them with concrete blocks resting on compacted soil. Installation of same will be far easier if you temporarily remove (and later replace) the deck boards where the tub will be placed--it's no fun working on your belly, trying to compact dirt and tight-fitting members on concrete blocks.
 
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Old 06-02-14, 06:35 AM
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Thank you very much for the responses.

Bridge, do you mean running new timber underneath the existing 2x6 perpendicular?

Basically I will be building a frame of timber underneath the existing deck frame with concrete supports? The deck will rest on these timbers and distribute the weight to the new concrete supports and old supports.'

For the bracing wood, would 4x4 work, or should I go bigger? I was thinking 4x4x12 with a concrete footing every 4'.

To kinda give you guys an idea of what I have, the deck span is 8' and the width of the deck is roughly 15'. The hot tub is 7'x7', it will sit against the house in the rear, and the two sides will be all but over the support footings of the deck. I could start at the house and run the new support beam 4' beyond the hot tub, or I could even go the full 15' if it would be better support. Would this work?

once all the deck boards are up it wont be that difficult to excavate a little ground to put in the new spans and supports. Let me know what you guys think of this.

To be on the safe side, I may just dig out spots and pour concrete footings for it.
 

Last edited by Xandrew245x; 06-02-14 at 07:08 AM.
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Old 06-02-14, 08:20 AM
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I have even seen spa's not supported by the deck when it's close to the ground. Gravel or blocks are placed on the ground to support the spa and the deck is built up to the edge of the spa. This would even give you the option of sinking the spa into the deck a bit for a more custom look. Just make sure you are able to open any access panels.
 
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Old 06-02-14, 12:17 PM
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Thanks for all the input everyone. We decided that we are going to pour a concrete slab to the right of the existing deck for the hot tub. We both feel that if we put it on the deck it is going to over crowd the deck. Even though it will cost a little more to do the concrete, it is going to be much easier than reinforcing the deck.
 
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Old 06-02-14, 02:41 PM
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it is going to over crowd the deck
Good move. We generally don't try to input our opinions too much unless we are asked to. But that would have been my suggestion if you had the option to do it. Good luck and thanks for letting us know of the change.
 
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Old 06-02-14, 04:12 PM
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Yeah, it is going to be a much better choice in the long run, I just dreaded doing it because we had to remove two bushes and a pond, but I got it all out today, and I only need to do a little bit of digging so the concrete will be at the same level of the rest of the deck. Already ordered all the materials to do the pad too, wasn't to much more than what it would cost to have braced the deck properly. Its a win win.

Now a new DIY task, pouring a concrete slab.
 
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Old 06-02-14, 08:17 PM
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If it's just you and one other person batching and pouring, after it's all done, you may have second thoughts about it being "much easier than reinforcing the deck." Concrete is very heavy, and not very time-forgiving. A typical 10' x 10' slab 4" thick will contain 5000 lb. (2-1/2 tons) of concrete.
 
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Old 06-03-14, 04:04 AM
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I think the foundation idea would be better than using up limited deck space, regardless of the materials, time and effort to pour it. He could always call in a load after forming
 
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Old 06-03-14, 10:10 AM
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I'm making the pad 7x10 and I'm going to divide it in two 5 foot sections, let one dry before doing the other.
 
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Old 06-03-14, 11:12 AM
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You will constantly be stepping directly from dirt/lawn on at least one side of your 7' x 7' tub if you pour the pad just 7' x 10', resulting in lots of miscellaneous yard debris getting into the water. Making the pad 10' x 10' would avoid that, along with providing a clear, solid working space completely around the tub for when it needs maintenance.
 
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Old 06-03-14, 01:17 PM
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That was a mistype, its going to be 8x10. The pad is going to be connected to the existing deck, only one way in and out of the hot tub and that is going to be the front which will have 3' of concrete slab plus the rest of the wooden deck, so no worries there. I appreciate the concern though.
 
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Old 06-06-14, 05:54 AM
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Poured one half of the slab last night and it actually came out decent. It really wasn't as hard as I thought it was going to be, once I caught the drift of how much concrete to place before screening it went smoothly. So far I have done this entire project myself, and with the help of a new holland sub compact tractor. I am glad I went this route instead of redoing the deck, the deck would have definatly been more of a headache then the concrete.
 
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Old 06-06-14, 07:13 AM
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Darn, I was hoping for pictures when I clicked on the thread.

Isn't it amazing what you can do with some tools. I wonder how I ever got by before getting a tractor & loader. Anymore I don't lift anything over 50 lbs into or out of my truck bed. That's what the tractor's for.
 
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Old 06-06-14, 08:35 AM
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I do have pictures.

Started with this. There was a pond, and two shrubs here that I had removed.



Built the forms and finished excavating. The chickens were helping me out.



Picture of the forms, started adding stone and tamping.



Stone finished on one side and added the rebar. I actually put another center piece in on both sides, I had leftover so I figured why not.



Here it is all finished up!



I'm lucky to have access to a tractor, its my parents, but they let me borrow it. They also have a business that has an enclosed building with garage door and a forklift, so I was able to take my whole skid of quikrete off and store there without breaking a sweat. I also have connections with a excavator so I got my stone for free
 
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Old 06-06-14, 10:26 AM
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You should have rented or borrowed a bull float, so you wouldn't be left with all of the hand float indentations in the concrete finish. You also should have used some additional rebar midway between those shown in the photo, along with some dobies. Also, I hope you used an expansion joint filler between the house brick and the slab--couldn't tell if it's there in the photo. If you forgot it, don't be surprised to see some edge spalling there after the first winter, when the slab heaves but the house doesn't.
 
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Old 06-06-14, 10:51 AM
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I agree about the float, all the reading I did said it could done be with a hand float, but after I see how it is now I wish I had done different, but it will be covered up so its not that big of a deal. I added more rebar and if by dobies you mean rebar supports like I have around the edges, I added a couple more of them in the middle.

I didn't add an expansion joint, all the reading I did, I didn't come across the use of an expansion joint at all, so I guess I will have some cracking there.
 
 

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