Hot tub on composite decking

[golferm]

Hi,

We're looking at purchasing a new house.

Its got an amazing composite deck.

Does anyone have experience in terms of can you put a hot tub on composite decking?

If so, what size should the supports be (2 x 10?) and how far apart??

With the way the market is right now, we'll have to likely leave the Bengal behind.  Oh well, time to look for a new tub!!

Thanks

Mark

[Bonibelle]

I believe Vinny has a composit deck. Hopefully he will check in and offer his help.

[cedar tub]

I believe it's standard building procedure for a deck to use 2x10 joists on 16" centers even if it is composite.  You will probably still need extra support.  Our deck has 6x6 posts set in concrete in the ground for the supports.  But, those are only on the corners and along the length...not directly under the deck.  It is also important to make sure the deck has a ledger between it and the house.  This should be bolted into something solid.  Joists should be attached to the ledger with hangers and not just nailed in. Around here there have been several bad deck collapses during parties and people have suffered broken bones, bad burns from grills and death.  Those occurred because the decks were simply nailed to a ledger that was also just nailed to the house.  Basically you have to make sure your deck can hold a minivan.  Our 488 gallons of water alone weighs 4,148lbs and that does not include the tub, people or anything else on the deck.

Our deck is about 24-in high at one end so, not too high.  I went to the big orange home improvement store and bought concrete support piers.  These supports have a 4x4 insert in the top.  I made sure that the supports under our tub ran across the joists and not the same direction of the joists.  Then, I marked the spots where the tub supports crossed each joist and that's where I placed the concrete supports.   Each support then has a 4x4 that supports the bottom of each joist.  I have 8 under the tub which has 488 gal of water in it.  I have very basic skills and did this myself.  Since your house is new, I'm sure a desperate seller will gladly have the extra support added for your spa.

[Vinny]

Boni's right, I do have a composite deck but my tub sits on a wood one which is below the main deck.

The WHOLE idea behind the deck holding a tub is the support structure. I believe that all composite decking can hold a tub ... I have timbertech decking which has it's decking potion raised from where it hits the struccture and they imformed me that that would also hold the tub.

Personally I think a lot of decks aren't built to hold a tub. I built mine to at least 125 lbs/sf with the tub's platform closer to 150 lbs/sft.

The building inspector was impressed at all the structral integrity that I had instralled. Here in Jersey there have been too many decks collapse because of insufficient or improper support. I told him I didn't want that to happen.

A deck can be reinforced to hold a tub ... it might be a bit of a pain but if the deck isn't built to hold the weight then it will eventually fail.

[tony]

I also have a composit deck with my tub sitting on a PT wood deck below the main deck.  Setting the tub on the composit decking is no problem, even though composit decking does not have the strength other materials have.  It all has to do with the proper support beneath.

[H823Putt]

I built my deck using composite decking. I used 2x8, 16" on center with double 2x10 girders 10' apart.


View from my uptairs bathroom.


But where my tub is I used 2x12's 12" on center suported by 6x6 posts.



Then I covered with 2x4 PT decking. The rest of the deck is covered with composite. The only reason I did not use composite under the tub was cost. At about $5/sq ft. I felt it a waste of money to cover.


All done.

[NE-Phil]

I used composite decking, too. Here are a few pictures I took at the time (June '05). I'm not positive of the details but I'm pretty sure those are laminated 2x12s, maybe 12" apart, with a 4x20 (?) support across the center.  You can see a few of the composite boards setting on it.
When I first saw it, I remember thinking we could probably support three filled hot tubs on it.

My contractor thought he better be safe than sorry and, considering the weight, I let him go with it. I'm pretty sure if we ever get another tornado, the deck will remain even if the house gets blown away!

Phil

Under the decking


Another detail - both ends of that center support rests on the mason blocks.

[Chas]

I have braced many decks over the years. Some, I simply put in RV jacks on blocks, placed at points which bore the most weight of the new tub. In some cases, a simple 4x4 across the top of two or three of these will do all you need.


Others I cut posts and set them on concrete piers.  Still others I doubled up or "sistered" one or two of the main support beams, or several of the joists.

I have also put in a new beam under the center of the tub, with two or three posts dedicated just to that beam.

Lots of options - none are all that hard to do. There have been plenty of times when the deck was already sagging before the tub went on - so I used screw jacks or the RV jacks above to not only brace for the tub, but level the deck! Ellis is one company which makes screw jacks for use with wooden posts - for the larger jobs.




HotSpring.com has a deck building program powered by DIY. You can use it to get ideas about adding support.



 8-)