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Leveling an established hot tub


csdude55

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I bought my house 17 years ago, and it had a Blue Ridge Spa by Jacuzzi already installed on a cement slab. It's roughly 80" x 80" and holds 4 people. If you're not familiar with it, I know that I've been able to use Gatsby parts as replacements.

Since then I had a deck built around it, and have personally replaced every piece of hardware on it; the only thing that hasn't been changed is the shell and pipes, seriously.

But over the years, that cement slab seems to have sunk on one side, so the tub is no longer even close to level. While sitting in it comfortably, one of the jets is so close to the surface that it shoots water out of the tub!

I emptied it today and used scrap wood around the top to shim it up and get it level: two corners had to be lifted by 2", and the third corner by 1".

But here's my question. I have no idea where the shim points on this tub would be, and from underneath I'm not even sure how it's sitting! There's nothing beneath the sitting areas, so there appears to be 18" or so of totally unsupported shell in each corner. The best I can tell, there's maybe 40" x 40" of the bottom of the shell that's actually sitting on the cement, but I can barely reach it from the front because I have to worm around the circuit board, pumps, and motors.

There's a plywood bottom underneath the motors, but it's way beyond rotted away. And most of the skirting is, too, so I can literally pull it apart with my fingers.

With it empty and lifted from the top, can I just shim the 3 corners of that 40" area (between the rotted plywood and shell) with cement pavers and plastic shims? Or is that really allowing too much pressure in the middle of that 40" area and in the sitting areas?

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Don't shim your tub - that's the best way to crack that shell once you fill it with 2500+ pounds of water.    I don't know the best answer to filling and leveling your tub, but you do need a flat surface, shimming will cause the shell to flex and crack once filled with water and people. 

Who knows how it's settled to the position it's currently in, but it likely happened slowly over time.  Good luck whatever you end up doing!  17 years is getting near the end of a lifespan for a product originally sold at Lowes as a budget-brand product. Course you've already replaced most all of the components as mentioned so I'm sure that helped increase the lifespan. 

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Unfortunately, @Cusser, I think Blue Ridge Spas went out of business sometime around 2000 😞  There are a small handful of companies that sell parts to fit it, but they're actually Gatsby instead of Blue Ridge Spa so even the OEM parts aren't available.

@ratchett, I thought the same thing when I first began replacing parts! Should I spend $200 on a part to keep an old hot tub alive? But at the time it was cheaper and easier than replacing... I probably have $1,000 invested in parts by now, but now there's literally nothing left that's original other than the PVC pipes and the shell. The PVC is cheap to replace, too, so unless the shell itself breaks then it SHOULD last another 15+ years!

I'm pretty sure that the old homeowners put it in themselves, and the cement slab is probably nowhere near as thick as it should be. I base that on the fact that they built a garage with a cement floor, too, that has cracked and leaks when it rains. So the right way to fix it would be to pull out the tub, repour the cement slab, and then put it back in... but with the deck built around it now, that's not as easy as it sounds! It'll probably mean tearing out a part of the deck and rebuilding it. Should I invest another $2,000+ to reset a 17+ year old hot tub?

(Moot question, really, cause I don't have $2,000 to blow on it! LOL)

But with it being so unlevel it's not usable, either. I have water to the rim on the front (where the control panel is), and the jet in the back left shoots water in the air!

Grrrrr 😠 

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Quote to have a local spa company lift it, jackhammer out the old concrete, then pour gravel, rebar, and a new cement slab... $1400. And the guy is an old high school friend, so that's probably a great price on it :'-(

I'm tempted to shim underneath with a 1x4 and then a 2x4, then shoot spray foam under it as thick as I can for additional support. In theory, it would hold the weight easily:

http://blog.achfoam.com/?p=1592

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1 hour ago, csdude55 said:

So the right way to fix it would be to pull out the tub, repour the cement slab, and then put it back in... but with the deck built around it now, that's not as easy as it sounds! It'll probably mean tearing out a part of the deck and rebuilding it. Should I invest another $2,000+ to reset a 17+ year old hot tub?

I think you need to ask yourself if you intend to replace the hottub in the future.   From the sound of it, I think you have no intention to replace the tub anytime soon.  I'd personally simply build a box frame (to hold in the gravel), fill partially with gravel, then build a frame for the hottub with 4x4's and some cross braces (slightly shorter than the tub so water runs off the side and not onto the pressure treated wood), then level it and fill with more gravel between the frame.  Might end up raising your tub another 5-10 inches out of the deck, but whatever as long as it works, right?

Not as elegant as pouring a new pad, but a fresh bed of gravel and level 4x4 base might be a cheap bandaid to get another decade out of that sucker!

 

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You're right, replacing it really isn't an option. $1400 for a new slab of concrete, plus at least $2700 for a new one (the cheapest I've found that would fit)? For something that I might use 5-10 times a year? I just don't see it happening.

When/if the shell cracks, I'll probably just pull it out, replace the deck boards where the hole is, and be done with it.

I like your idea of giving it a gravel bed... maybe paver base? I'll still have to pull the whole tub out, though, which is much easier said than done! To get it to lift 2" took my full body weight... with the water logged / rotted skirting and plywood bottom, it has to be 500lbs. Maybe I could get 4 car jacks under there to lift it up a foot, then build the frame under it? I'll have to think on that one.

I'm attaching a couple of pics for you. The part that I circled in red is the only part touching the cement slab. It measures 30" left to right, a little more than that front to back; you can see it's odd shaped, so it's hard to be exact. But a 48" x 48" frame would be more than enough to fit under it.

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IMO If that middle part is the only inside section bearing weight I would think ya you can shim it, be sensible and try and distribute and carry as much load as possible over the greatest area(s) under the tub. 

But I think ratchet has the best idea, use gravel to make a temporary level surface. It's more work but there's almost zero risk of breaking your tub that way!

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You cannot shim an edge, your shims must go from one side to the other or it will crack the frame and/or shell. This is not a maybe. The majority of the weight falls in the footwell, but the edges also support, as do any pillars in the foam insulation. Any shims must line up with the bottom support framing.

Spray foam will not support your spa, though it may fill gaps between the supports. It is also not waterproof so will soak and get moldy too.

If I don't have an airbag I like to get 2" straps under the spa and about 4 guys to lift it. Have some 4x4s ready to kick under it across the hole and you won't have to move it, just lift it then slide it on the 4x4s. I would stand it up and replace any rotted wood framing while it's out.

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  • 1 month later...

I wanted to give you all an update, since you were all so helpful!

For my project, I had to level my deck AND the hot tub; the deck had sunken down around the hot tub because the contractor didn't put any supports under it.

I first emptied the hot tub, then had to chisel out the 2x4 trim that went under it. You can kind of see that trim in my pics before... it was originally stained brown, but it had mostly rotted away. Then I placed 2x6s under the edges so that it would raise when I raised the deck, and then I could see what to do underneath.

Next step, I used a bumper jack at each corner to raise and level the deck. Now THAT was a pain!! I had my girlfriend stand on top of the deck with a level and yell when I was good, but one section under the deck only gave me about 18" of clearance! Not to mention the spiders and all the freakin' mosquitoes 😠  But I got it done.

From here I could see the bottom right corner needed to be shimmed by about 1 1/2", the bottom left corner by about 1", and the top right corner by about 1/2". Not exactly what I had estimated before, so it's already good that I'm taking these extra steps!

Next, I used pressure treated 2x4s to build a frame kind of snug around the bottom of the tub, sitting on top of the cement slab. I wanted to line it with plastic but I couldn't get the plastic to slide under the top left corner of the hot tub, and I might end up regretting that.

Then I poured about 1/2 bag of leveling sand into the frame that I built, then took a 1/2" furring strip cut to 4' long to slide the sand under the hot tub. That took a little work to get past the tubes and everything! But once I got it in place I repeated adding sand several times to really pack it in, trying to make sure that the furring strip reached both sides of the hot tub at the same time.

Once I thought it was really packed in well, I took another furring strip and placed it against the one I was using to slide, then tapped it with a hammer to really wedge it in there. Not TOO hard, I wanted to raise the tub off of those 2x6's by maybe 1/64"... just enough to release the pressure.

Then I poured more sand, and repeated the process with a 1" strip.

Then I poured more sand, and repeated with a pressure treated 2x4 (so really 1 1/2" thick). When that was done, everything had been shimmed and packed with leveling sand.

Next, I used cinder blocks and wood to add support under the seats. These weren't originally supported before, but I figure... why not? Since I'm under here, dirty, sore, and covered in bug bites, I might as well make the most of it! LOL

From there I filled the tub up, just a little at a time, and kept an eye out for any movement or sounds. I filled it about 1/8th, then let it sit overnight and repeated the next day. I didn't have any issues at all, so after it was filled and heated, we gave it a "test run" with two of us in there... no problems at all!

Last step, I cut new trim out of those 2x6s, stained it, slid it under the edge of the tub, and used structural screws from underneath to mount them in place. I have 1" of wood under the edge of the tub, and 5" showing; I specifically wanted it to be wide enough to sit wine glasses or whatever. I have some pics of the trim below... I took some underneath to show the finished shimming, but you really can't make anything out so I didn't post them.

Either way, I hope this helps others with the same problem in the future!

 

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