Spa Deck Specs

[dannydan]

Hi all. Wasn't sure where to post this one.
I am considering a new spa which will weigh in excess of 4000 lbs. I want to build it myself, but am unsure of the details of the support to the deck/platform on which it will sit.

It will be 8'x8' in size, level with the ground in front and about 2' off the ground in back, due to the slope of the yard at that point.
My rough idea is that I will need 6x6 posts sitting on all corners as well as one on each side between the corner posts (a total of eight), all atop concrete support footers. Then a 2x12 doubled frame, with 2x12's 12" on center, with the "normal" decking boards on top.
Is this too much? I don't want any trouble later, but even a deck that's only 8'x8' built this way will be expensive.

Thanks! [img]/forums/images/icons/grin.gif[/img]

[johnday]

Danny; A little more info please. You said 8X8. Is that the size of the spa, or the size of the deck to support it? I built a deck a few years ago for this purpose, the building inspector was impressed. The guy in that area was pretty anal, so if it pleased him, it should yours. Have you asked your local building dept. about this? That is what those guys get paid for. They may require an engineers stamp on your project too.

When I get a little more time today and can figure out how to scan and post a drawing, I'll show you what I did. [img]/forums/images/icons/grin.gif[/img]

[johnday]

Danny; Here's the drawing I spoke of. Hope it helps. Bear in mind I'm NOT an engineer, and this is only what I used with building dept approval. The posts are all on 4' centers, the 2X12 joists are on 12" centers. I did not show a rim joist, that's pretty self explaining. You could use regular 5/4 deck boards, or for a little more stability, 2X6's. Regardless, don't do what many Joe Homeowners do, instead butt the boards right up against each other with no gap. The boards will shrink and you'll wind up with a gaping gap. Also the new ACQ treatment for wood requires at least triple galvanized fasteners, stainless is the best way to go. At any rate any hardware or fasteners have to be high quality. If your lucky, you may be able to get 6X6's treated to at least .60 retention with the old CCA treatment. The CCA treatment can still be used in commercial applications and can be had in the larger sized lumber.

Good luck, hope I helped out. [img]/forums/images/icons/grin.gif[/img]

[dannydan]

Great, thanks alot guys for taking the time to post on this one. All great ideas.
I am now of version 1.2 of the plan, and am going to make the new deck 12' square, adding some steps later to make it blend in more with the existing deck. Should look nicer as someone had mentioned, as well as more room for cover, stepping in and out, etc.

I hope that this isn't one of those "if you have to ask you should not be doing this project" questions, but what is the general rule for footings? I am in cold country up here and with that kind of weight do I need to go down to the frostline?
And do I need to go down that far anyway?
I have seen a "2'x2' rule" where the footer is 2x2x2 deep. I would think that I would not want this deck "floating" because of the weight and hurting the new spa by not having proper support for it.
The dealer I was at didn't have any advice on the structure, most likely due to possible liability and the desire to have his crew do the work. There's not a whole lot of local dealers around here either.
Sounds like in my situation I would be off to a good start to get the ground as level and as low as I can. (my limitation is the existing deck that I plan to use for the entry point to the spa).
Then depending on the footer issue, I may go the concrete route, depending on local lumber pricing.
I hate to be a sap and have local contractors come out and estimate this when I have no intention of using them.
My previous experience was from working with my Dad, he was a carpenter. So I know basic framing stuff and have been exposed to most everything else except foundation design and requirements.
I am spending about all I can afford on the spa so I have to do this myself - huge difference in price, and I like to think that my work rivals the professional's.
And of course, more seat time!
Any and all ideas are welcome, again thanks to those that have already taken the time to help.
[img]/forums/images/icons/grin.gif[/img] [img]/forums/images/icons/grin.gif[/img] [img]/forums/images/icons/grin.gif[/img] [img]/forums/images/icons/grin.gif[/img]

[scbrittain]

Danny,
try out this link. It is span calculator so you can figure out what span you can use. It lets you select wood species, weight limit and size. Hope it helps Steve
http://www.awc.org/calculators/span/...rcalcstyle.asp

[ljh2]

I'm not a pro at this, but I'd expect that to avoid any having frost-heave issues put stress on your spa, you would want to have concrete footers that extend at least 6 inches below the frost line. If you go with a floating design, you would need for the entire platform to rise/fall together, not have each pole float individually. Of course, poles sitting of footings bedded 6 inches below the frost line on solid undisturbed/compacted soil should stay put too.

You could/should probably check with your local code department for their suggestions/requirements. I agree that it is probably bad-form to have a contractor come out and spec the job for you if you don't have any expectation of hiring them to perform the work. On the other hand, the local government code office is paid by your tax dollars. While codes can be a pain in the butt, they do generally provide you a safe guideline and help keep you covered if you ever need to exercise your insurance policy.

good luck with your project,
larry