Do I Need To Support My Deck

[Tubber McGee]

Taking delivery on my Vanguard this week. I started prepping my deck when my neighbor says I need to put cinder blocks under the deck! I have never heard of this!

My deck in fairly new - built correctly - 2 feet off the ground with all the correct support.

Should a tub be OK on this deck? Does it need any additional support such as cinder blocks?

Thks!

[hottublady]

[currier1]

Taking delivery on my Vanguard this week. I started prepping my deck when my neighbor says I need to put cinder blocks under the deck! I have never heard of this!

My deck in fairly new - built correctly - 2 feet off the ground with all the correct support.

Should a tub be OK on this deck? Does it need any additional support such as cinder blocks?

Thks!

I am not a structural engineer, but I am a contractor and I'd be surprised if your deck was capable of supporting the Vanguard's nearly 5,000# filled load.

Depending on how long the joists are spanning on your deck and whether or not you have any mid-span carrying beams you could definitely be overloading your deck's weight capacity.

My recommendation? Get a structural engineer to check it for you. Compared to the cost of your spa and the potential damage you might be doing to your deck and your new spa, it'd definitely be worth your time and money.

Engineer's I work with charge $100 to $150/hour - including field measurements and calculations in his office, I'd be surprised if he spends more than a few hours helping you out.

[DaveR]

Taking delivery on my Vanguard this week. I started prepping my deck when my neighbor says I need to put cinder blocks under the deck! I have never heard of this!

My deck in fairly new - built correctly - 2 feet off the ground with all the correct support.

Should a tub be OK on this deck? Does it need any additional support such as cinder blocks?

Thks!

If your deck wasn't built to support a hot tub it is most likely built to support 40lb per sq ft. You will need to support at least 120-160 lb per sq ft.

Cinder blocks placed on the ground will not do the trick either, they will eventually sink into the ground and as they do it will put stress on the tub and you will get cracks. The weight must rest on piers dug to the depth required based on where you live / local code.

Spending a little money now could will save you quite a bit later on.

Dave

[djousma]

I agree. Plus 5000# of water/hot tub/people 24 inches off the ground, can create a lot of leverage. You can pay an engineer to come out, or you can just add additional mid-span load carrying beams under the hot tub area, with 4x4(or 6x6) supports in concrete and be done with it. If your deck is attached to the house you dont want all the weight hanging from the joist hangers alone.

[Damian]

All replies are giving you good sound advise. Don't put that tub on your deck until you know its structurally sound.

[footie]

What you need to do is unscrew the planks were the tub will rest and build up concrete blocks to the level of your decking or at the very least build up the blocks to the level of the supporting runs that the planks are screwed to. This should do the job.

The only thing about decking is it will rot, concrete pad is always the best solution.

[Dr. Spa]

build up concrete blocks to the level of your decking or at the very least build up the blocks to the level of the supporting runs that the planks are screwed to. This should do the job.

How are you addressing the issue of soil compaction under these concrete blocks (future settling. e.g total loss of support)? What are your concerns of possible frost heave you're taking into consideration?...there's more, but ya hopefully get the point :-)

OP, be very careful taking advise from people you don't know. What can be good intentions, could result in deck failure and unwarranted catastrophic damage to your spa. What you are asking requires knowledge of your specific area, a college degree, specific licensing, and ideally liability insurance as well as errors and omissions insurance.

[Tubber McGee]

OK - just talked with my HotSpring salesperson to address my concerns - who I trust and has been great to deal with! I already purchaed the tub - so his advice really does not affect the sale as he knows if the deck does not work out - I would pour a cement slap!

Anyway, he stated that they have put tubs on hundreds of decks without any problems - EVER. And this is high volume dealer with 7 or 8 stores througout the area!

Though I do believe this could be an issue in some cases - I think I should be OK. I do have a friend who is a builder who is coming over tomorrow to look at the deck. It was built very nice and overbuilt.

Thinking I will go underneath and at least wedge up a couple cinder blocks. Thinking I would put them on small cement paver for more stability! Instead of just laying on the ground!

Thoughts - am I assuming I will be fine and possible in for trouble in the future!

What a pain!

Thanks

[spawn]

Tubber - It may be that what your dealer has told you is absolutely correct - that your existing deck is adequate to support the tub with water and people. No doubt, hot tubs are frequently installed on decks, but often decks have been designed to support such a load. The typical deck is not designed to support the load of a hot tub. It seems rather optimisitc for someone to advise you that it will not be a problem without knowing the size of members, span lengths, wood grade, footing support conditions, etc.

I may be mistaken but I thought that Hot Springs or some other manufacturer had a deck design program on thier website - maybe one of the other forum members can point you in the right direction. You could see how your deck compares to a deck designed to support a tub and perhaps get some reassurance or find out that you have an issue. In addition to the other advice you are getting, I add one more idea for you to consider. With your deck 2' off the ground it may be possible for you to pull the deck boards, reconfigure the framing and pour a concrete slab on grade, set the tub in and reinstall the deck boards with the tub set it. I know that sounds like more work and $ but it is an option to trying to reinforce a deck. Having a tub set 15" - 18" down into a deck can be very nice. I actually prefer the look aethetically to a tub setting on top of a deck and access is made easier as you don't need the steps. Just a thought that may or may not make sense for you but I thought I would throw it out.

As Dr. Spa says take all advise here with a grain of salt, included this!

[njmurvin]

Taking delivery on my Vanguard this week. I started prepping my deck when my neighbor says I need to put cinder blocks under the deck! I have never heard of this!

My deck in fairly new - built correctly - 2 feet off the ground with all the correct support.

Should a tub be OK on this deck? Does it need any additional support such as cinder blocks?

Thks!

Maybe you should consider opening up the deck where the spa goes and pour a slab on the ground for the spa to rest on. It will be much more stable, will look more like it is part of the deck (that sunken tub look) and will be a lot easier to get in and out of. This is exactly how mine is built into my gazebo.

[footie]

Maybe you should consider opening up the deck where the spa goes and pour a slab on the ground for the spa to rest on. It will be much more stable, will look more like it is part of the deck (that sunken tub look) and will be a lot easier to get in and out of. This is exactly how mine is built into my gazebo.

True, though you also need to remember and add some form of excess to the pumping gear and eqipment, otherwise it's a drain before lifting the tub every time something goes wrong.

[Gouie]

Just posted on this very topic - http://www.poolspaforum.com/forum/index.php?showtopic=26457. As mentioned, if the deck was not build with the intention of putting this much weight on it, it will not support it.

[DaveR]

I was very interested that several people said that there would be no problem installing the hot tub on the deck with no modifications. The only way this made sense to me was if the building codes in your area made everyone build their decks sturdy enough to support one.

I overbuilt my deck so at some point I could add a 3 season porch. I used 2x12 spaced every 16 inches the span between support beams (triple 2x12s) is 12 feet. I was told to support a hot tub I would have to add 2 supporting beams & posts under the tub, I have several contractors in the family and thats what they did on their decks.

Check this out:

ideas-for-deck-designs.com/beam_size.html

hopefully this might help you avoid a costly mistake.

Best of luck,

Dave

[njmurvin]

Maybe you should consider opening up the deck where the spa goes and pour a slab on the ground for the spa to rest on. It will be much more stable, will look more like it is part of the deck (that sunken tub look) and will be a lot easier to get in and out of. This is exactly how mine is built into my gazebo.

True, though you also need to remember and add some form of excess to the pumping gear and eqipment, otherwise it's a drain before lifting the tub every time something goes wrong.

Exactly. In my case the spa sits at the rear edge of the octagon. I simply positioned the equipment side of the spa to be exposed to rear for access. If that's not possible, he would have to build a removable section of the deck to gain access.

[Fatlip]

Don't even let somebody say it will hold that spa, you are talking about big problems later, put in 3 more 6 by 6 post sitting on concrete footings at lest 2 ft deep and run a double banded beam across them supporting the joists and double band the joists at the spa area. If joists are less than 16in on center you might not need the double banding, but would be a hell of allot stronger. Notch the post for the beam to rest on and nail it up. That spa will not move then and is cheap insurance to do. That spa dealer must be nuts saying that with out looking at your deck. You might have enough posts in place but are they on concrete footers. If not they will sink with all the weight. Do it right, its easy and costs will be around 50.00 to 100.00. Also just hammer up the decking boards from underneath where the spa will be centered or if screwed down its even easier to get to area the new posts and beam will be.

Rick

[JimKW]

Don't even let somebody say it will hold that spa, you are talking about big problems later, put in 3 more 6 by 6 post sitting on concrete footings at lest 2 ft deep and run a double banded beam across them supporting the joists and double band the joists at the spa area. If joists are less than 16in on center you might not need the double banding, but would be a hell of allot stronger. Notch the post for the beam to rest on and nail it up. That spa will not move then and is cheap insurance to do. That spa dealer must be nuts saying that with out looking at your deck. You might have enough posts in place but are they on concrete footers. If not they will sink with all the weight. Do it right, its easy and costs will be around 50.00 to 100.00. Also just hammer up the decking boards from underneath where the spa will be centered or if screwed down its even easier to get to area the new posts and beam will be.

Rick

If not sinking the hot tub down in the deck and putting it on a slab, this is exactly what I would do regardless of what others are saying.

[tylemandan]

It states in the pre-delivery booklet (which you should have) for Hot Spring that a deck needs to support 110 lb per square foot for a Vanguard. If you aren't certain that your deck supports this then contact a qualified contractor or engineer or deck builder. Don't take chances. The pre-delivery guide states that the Vanguard weighs 4,951 lbs with water and people. Better safe than sorry.

[spawn]

Okay tubber - I found the deck design program I referred to earlier. Go to the Hot Springs Home Page, and under "Backyard Planning" click on 3D Hot Tub Deck Design Tool. You can get an idea of how your deck compares to a deck designed to support a tub. I have never opened this program but I am assuming that it will design a deck appropriate for supporting a full tub.

[footie]

There is one certainty, and that is that cement slabs are 100% approved by all hot tub manufacturers. Personally I think that if it's at all possible I would try and cut out a section of decking and pour in a cement slab for your tub to sit on, of course remembering to leave some form of excess to maintenance for the tub's equipment. The very fact that your decking sits two foot off the ground means that you only need to pour the slab on top of the ground instead of sinking it so it's something that you and a couple of mates could easily do in an afternoon.

I would seriously look at this option if I were you.

[DaveR]

There is one certainty, and that is that cement slabs are 100% approved by all hot tub manufacturers.

I would qualify the cement slab being 100% approved with "if done properly". My wife is a spa tech and has seen dozens of cement slabs either breaking up or tilting because they were not done correctly.

Dave

[footie]

There is one certainty, and that is that cement slabs are 100% approved by all hot tub manufacturers.

I would qualify the cement slab being 100% approved with "if done properly". My wife is a spa tech and has seen dozens of cement slabs either breaking up or tilting because they were not done correctly.

Dave

Of course it needs to be done properly, but it's hardly rocket science. If your wife has seen lots of poorly prepared slabs then American workmanship must not be up to much. (j/k)

[DaveR]

Of course it needs to be done properly, but it's hardly rocket science. If your wife has seen lots of poorly prepared slabs then American workmanship must not be up to much. (j/k)

You'd be amazed at what she see's. I'd bet close to 100% of the failed slabs were done by DIY'ers either trying to save $, used the wrong materials, and/or just didn't know what it took to do it properly.

One of Kaye's pool clients just self installed a used hot tub on their cement pool apron. 2 weeks later it cracked, the owner installed the apron a few years earlier and hadn't done the right soil prep or used any re-rod. The thickness varied from 2" to 6".

We are "cement free" and installed our tub on 6" of class 5 (road base gravel) compacted every 2 inches topped off with 4 inches of pea gravel for drainage.