Adequate hot tub platform?

[javasteve]

I will be taking delivery of a hot tub soon, and what I thought was an iron clad platform idea is starting to give me second thoughts.  I don't want to change the premise dramatically, but any advice will be welcome.

I plan to build a deck like platform just off of my deck.  Based on heights we will be able to step off the deck, over about a 6" lip of the tub, into the tub.  I am building the platform 8' x 8', using 2x6's for the frame, 2x6's spaced 16" on center, and then 2X6 deck planking on top.  At first I was going to place this directly on the ground, but now I have decided to pour footers at each corner, and one directly in the middle, for the corners and one of the joists to rest on.  The footers will be poured about 24" deep. and come up to grade, and I will make sure that all 5 footers are level.
The house is in Sussex County Delaware with sandy soil.

Does that type of platform sound adequate?

[jim97219]

This is a post you should read:
http://www.whatsthebest-hottub.com/cgi-bin/yabb/YaBB.pl?board=wtb-hottub;action=display;num=1139356183.  

  800 pounds for the tub empty.
3,350 pounds for 400 gallons of water.  
  700 pounds for 4 people @ 175# each.
4,850 pounds total.  

Divide that by 64 and you're talking over 75 pounds per square foot.  I'm not a construction guy but I don't think 2x6's on 16" centers is going to do the job.  Come to think of it, that's about how my deck is built and I can feel some bounce in it when I jump up and down on it.  I'm I'm just a tall, skinny kind of guy.

In the post I've linked, mxw128 has his tub on 2x10's, 12" on center, with a second doubled support in the middle.  That sounds REALLY solid and adequate.

I'd suggest starting with a chat with your dealer.  At the very least, he/she should be able to get you in touch with a construction type or even an engineer if needed.

Good luck

Jim

[Brewman]

Have a chat with whoever enforces the building code in your city- tell them what you want to build, and they should be able to help you out.  

[lawdawgva]

Definately check with your city or county and build to code, but you should be fine with the 2x6's on 16" centers if allowed.    The key to no sag is not to support the deck only by the header boards as most builders do because this will allow the joists to droop in the middle over long runs.

I sunk 4x4's in concrete about 3' in from each corner of my deck and then bolted a 2x8x16 to each side of the 4x4's after getting them level of course.   Then, I built my deck frame out of 2x6x12's running perpendicular and sitting on top of the 2x8's.  The weight of the deck material holds itself down in addition to 4 galvenized steel "hurricane straps".

I have  a 355 gal. Sovreign on one corner of this deck with absolutely no sag, creaks or other problems.  The great thing is, if your code allows it, instead of sinking in concrete, you can buy those precast concrete "deck piers" from Lowes/Home Depot and sit them right on top of the ground.  They have slots for 2 bys and a large indentation for receiving the end of a 4 by.  Wish I had known about those before I built my deck!  LOL

PM me if you want to know more about my deck plans.  I just finished adding another addition to my deck so the whole thing is now 16 x 24 and turned out really well.  Good luck!

-Sarge

[Vinny]

I built my tub's deck for minimum of 150 lbs PSF. It's 8'x8' and I used 6 - 12" concrete pads 36" deep, 6x6 posts, doubled 2x10 beams, 2x10 joists 16"oc and 2x6 planking. I also used enough brackets, bolts and associated hardware that you can park a tank on it.

As jim97219 said, do the calculations:

Tub = how many lbs
Water = 8 lbs per gallon x how many gallons
People = # of people x  average weight per person (go large on this).
Weight of wood to build deck
Snow load on cover

Keep adding it up and you'll see how heavy you will get.

The deck you plan is too flimsy IMO, get the info on the weights and go to a lumber yard or Home Depot and have them do the plans.

The other thing is the height of the tub's lip. As we get older, it gets harder to get up and down on things and you should consider putting the tub with the height of a seat or step inside the tub (approximately). It makes it real easy to get in or out, just sit on the edge and swing your feet over ... really easy!

Good Luck!

[ssbraun]

I'm with Vinny and Jim.  I used to frame houses, and 16" centres is too far apart IMO...it costs very little more to go 12" centres and 2x10's for the small size of a typical spa.  Those pier blocks are even better if set on sidewalk blocks to spread out the weight over larger surface area at the base (less likelihood of settling).  Don't cut corners here...it may become a real pain later if you do.  Good luck .

Steve

[Snowbird]

Our hot tub room is built 10 feet up where our old deck used to be.

It sits on four 6x6 posts in holes 36 inches deep with a 12 inch bed of concrete in the bottom of each. Theses 4 posts are positioned to be directly under the hot tub.

Atop the posts are two double 2x12 beams with one end sitting on the block wall of the basement so each beam is supported in three places.  The posts are tenoned between the doubled beams then bolted together.

Across these two beams are 2x12's on 16 inch centers with 3/4 inch T&G OSB decking as the floor.

All this supports the roof and two exterior walls of a 12x18 room plus a Jacuzzi 385 that comes in at 6000 pounds wet.

We put the tub in this past December and so far everything is good, but I don't expect anything to happen until the spring thaw.

This seems like it is good enough to do the job, but I am not too worried about it since my builder assured me there was sufficient support.  If anything happens, he'll be back - for free.

[windsurfdog]

Ok.......here's mine:

Total deck/stairs, 48'x16',  is 8' off grade with 8x8 pillars buried 5' encased in concrete topped with beams composed of 3 2x12's topped with 2x10 joists on 16" centers decked with 2x6's.  Under the hottub, there is a 12'x12' area that has 6 of the aforementioned pillars and the 2x10 joists are on 8" centers.  This sucker ain't goin' anywhere.

Overbuilt?  Yep.  Am I happy now?  You bet.  Would I be happy after the fact with a marginally engineered deck that possibly wouldn't stand the test of time?  No way.  Better to err on the side of overbuilding than end up with something that might constantly worry you.

[lawdawgva]

It certainly won't bust your budget to throw a few extra joists in if you havent constructed yet and are still in the planning phase, but 16" centers will work just fine on an existing deck.

Chances are your home's floor joists are on 16" centers which give you about 14 1/2" from joist edge to joist edge.  A side by side refrigerator is about 500 pounds on a 6 sq ft footprint.  This is about 83 pounds per square foot which is equal to or slightly more than most hottubs.

-Sarge

[ssbraun]

Sarge, just one note (not trying to nit-pick!!)...the 2 x 6's in the original question would not be suitable for floor joists in a typical home, and won't support the weight of a 2 x 10 or 2 x 12 or a truss-joist.  I still go along with the over-built thing for the small extra cost

Steve

[Vinny]

I want to comment on the "correct" lumber to use and WSD and ssbraun said it best with the "overbuilt" comments.

2x6's may be good if you support them correctly and lawdawgva probably did so but unfortunately some people don't.

I'm a big guy and I walked onto a friends deck and it bounced! Not a lot but enough to notice and he passed the township inspection and he used 2x8's. When I built my deck, I made sure it didn't bounce and I may have overkilled it structurely but I know that nothing will collapse. There's too many stories about decks here in NJ collapsing under the weight of a bunch of people on the deck. I believe that the extra money I spent is worth it for piece of mind.

[windsurfdog]

Chances are your home's floor joists are on 16" centers which give you about 14 1/2" from joist edge to joist edge.  A side by side refrigerator is about 500 pounds on a 6 sq ft footprint.  This is about 83 pounds per square foot which is equal to or slightly more than most hottubs.

I'd not figure less than 125 lbs./sq. ft.  
Can less work.....maybe.  Can this work.......definitely.