Platform/Deck for Spa


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Old 04-07-13, 06:13 PM
J
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Platform/Deck for Spa

Hello,

I recently purchased a home and am itching to start a new project with the weather starting to warm up. This forum seems like it has a pretty good community for feedback of construction projects. I did some prior searching and noticed some people had similar questions to what Im about to ask, but they all varied just enough that I had to ask it per my own scenario.

I am in the process of planning an 8 x 8 deck/platform for a future hot tub purchase. I have figured 4500#s for the hot tub with water, and another 1500#s for people = 6000#s. The platform will be covered so there is no need to worry about snow load. I am thinking of designing as follows:

Concrete footings (4ea): 48 deep, 10 diameter sonotube, with 20 bigfoot bases at each corner. (I live in Alaska)
PT Posts (4ea): 6x6 cut 2 3 high at each corner.
Ledgers (2ea): 2ea. 2 x 10 bolted together, essentially making a 4 x 10 ledger on each side.
Joists: 2x10 at 12 O.C.
Plywood Decking (2ea): 4x8 for decking. Although I may change this to regular planking before the install.

Do you think this is too little, too much, or juuuuust right? Maybe add another post and footing in the center? Im not an engineer, but I did some calculations and it seemed to work out. But that didnt take into account deflection, wind, or any of that good stuff.

Thanks,

John
 
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Old 04-07-13, 07:01 PM
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What exactly will cover this platform to protect it from snow loads? Meaning some form of corner columns need to tie in to your 6 x 6s, unless you're going with two separate support systems. Also, I would never consider using plywood for a flooring surface--too many performance and durability problems. Composite or PT wood planking is a better option. Using ledgers for attachment to the house is also losing favor, instead going with free-standing units for a number of practical reasons.
 
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Old 04-07-13, 07:24 PM
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Thanks for the quick reply bridgeman. I am going to build the platform adjacent to a deck that is covered from the roof of my house. So yes, essentially I am building a second freestanding unit. If possible I would like to avoid using existing posting as Im not sure what standards it was built to (1970s house). I will not be attaching the ledger to my house, but to the 6x6's. Maybe that was the wrong choice of wording?

Good point with the plywood; PT planking it is.

All that being said, do you think that is a reasonable design for this application?

Thanks for the help.
 
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Old 04-08-13, 10:53 AM
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So what you're calling ledgers (doubled 2 x 10s) are actually serving as beams, between which joists are running, right? Using joist hangers? Sounds adequate to me, but I'm not a hot tub platform expert.

One thing I can tell you, however. In the last 2 places I owned that had pre-existing hot tubs, I gave both of them away, just to get rid of them and make better use of the space. Also, I would think the climate in Alaska wouldn't be conducive to getting much use out of the thing--like maybe 3 months out of 12? And you'll be paying dearly for your source of heat, too, trying to extend the time you can use it.
 
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Old 04-08-13, 12:57 PM
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Thats exactly right; they will act as beams with joists connecting between the two on hangars.

We only average 20 degrees in the winter for this particular area of the state, so it wont have a problem keeping up. Out cost of electricity is a whole different story! Ha.

The deck I build adjacent to the existing will fit in nicely with or without the hottub. So, if I do find that we dont use it much I can sell it and can utilize the space as a lower tiered deck. Yet another reason to use planking and not plywood.

Thanks again for your input bridgeman.
 
 

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