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I need to raise a hot tub out of the deck in our back yard to address a critter problem (rodents have been living underneath so I need to clean it and critter-proof it.) The deck seems to have been built around the hot tub and it doesn't seem possible to disassemble the deck in a non-destructive way, so I'd like to hoist the hot tub directly upwards. Currently there is 23" of hot tub above the deck and 20" below the deck, resting on concrete. There is maybe 2" of clearance between the sides of the hot tub and the deck.

What I have in mind is to build a gantry crane similar to this gentleman's, rent two half-ton chain hoists to hang from the crane on either side of the hot tub, then raise it up and support it with wood braces or cinder blocks while I work on it, or possibly flip it on its side on top of the deck. Afterwards I would use the hoists to lower it back into place.

Because I'm hoping not to have to do this again, I'd like to avoid investing too much in disposable lumber and hardware. I was thinking of using 4x4s for the vertical posts, 2x6s for the horizontal support at the top, and 2x4s for the diagonal supports. To secure these pieces together I would use lag bolts with washers and nuts.

Does this plan make sense? I have fairly limited woodworking experience. What size of bolts would be sufficient? I was thinking 1/2" but they are somewhat expensive and I expect may be overkill. Here are a couple drawings of what I have in mind (front and side view):

gantry crane with hot tub in raised position

side view of vertical support

Edit 1:

Here is a photo of the hot tub with some of the surrounding deck boards removed:

hot tub with partially exposed deck

I am guessing the hot tub weighs something like 800 lbs, plus or minus 200.

The double 2x6 support resting on top of the tub in the picture above was slid out of the hangers built in to the deck; I imagine it was built that way to allow for easy access to the motor on that side. The other joists surrounding the tub are not easily removable. If I'm unable to lift the tub out I think I would need to disassemble and rebuild that entire portion of the deck which is about 14x14' including several steps.

To connect the tub to the hoist I was thinking of using screw eyes in the wood at the base of the tub. I haven't really figured that part out yet, so my drawing is a bit misleading.

Another consideration: I don't know if I will be successful at critter-proofing the thing on my first attempt, which is partly why I'd like to build a reusable crane in case I need to do this again 6 months from now (as opposed to destroying and rebuilding the deck multiple times)

Edit 2:

Some more photos:

wide view of deck and hot tub

corner with deck boards removed

looking down at deck joists

clearance between joists and tub

looking down at motor area

looking into motor area

electrical connection

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    How are you going to attach the hot tub to the crane? What's the hot tub made of? – Steve Sether Oct 16 '20 at 4:03
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    Plumbing connections? – manassehkatz-Moving 2 Codidact Oct 16 '20 at 4:53
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    What is the deck made of? Can the deck support the weight of the gantry and hot tub? I'd think so only iff it is a wood or concrete deck. If it is wood, you'd be better off figuring out how to remove the decking and work on the tub in situ. Attaching the tub to the crane will be the most difficult. It isn't like the hot tub has lift points you can hook into. You'd have to slip straps underneath the hot tub. You'll need to do some extra tricky rigging to balance everything and keep the straps from crushing the sides inward. Post pictures of the deck and tub. – Jon Oct 16 '20 at 5:25
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    Whatever solution you go with, "overkill" in construction and support is better than "kill you" in execution. A few bucks (even a few hundred) is better than hospital bills or loss of life. Even if the tub isn't that heavy, if something fails, it could be deadly. – FreeMan Oct 16 '20 at 14:14
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    If somebody said to me, I can't figure out how to remove deck boards, so I'm going to improvise my own hot tub lift, and use the cheapest bolts I can to do it, I would ask that person to seriously reconsider their entire plan, and suggest they get an insured handyman or pest control service to help with the problem. That's what I'm suggesting to you now. Your plan is a danger to your life and property. Be safe, friend! Post some pics and maybe we can help you work out how to access the tub area for cleaning without removing it. – Jeff Wheeler Oct 16 '20 at 16:00
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I'd be cautious building something like this with limited woodworking experience. Typical framing like this would have 1/2" bolts and your rough sketch is similar to other stable gantries. I see this a lot in Florida where people have partially below grade hot tubes and need to raise them for drain and piping replacement. Renting a gantry seems to be the popular way to do this. Some with wheels on the base allow you to move it out of the way to do your work. See picture below. This might save you some time and keep you from having to build one yourself.

enter image description here

I have no business interest in any rental companies.

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  • Thanks – this might be a good option, but the closest place I could rent it from is a 2-hr drive each way, and it would cost about $300/week. I figure I can build one myself for about $100, and be able to reuse it in the future or disassemble it and reuse the lumber and hardware. The homemade version in the video I linked looks fairly straightforward. – gosko Oct 17 '20 at 2:25

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