Build-it-yourself wood hot tub - crazy?
May 1, 2013 6:20 PM   Subscribe

Build-it-yourself wood hot tub - good weekend project for an amateur, or more difficult than that?

I spent some time in a wood hot tub up in redwood country last month and found it unexpectedly delightful. I loved how much deeper it was than your usual plastic or in-ground spas, and I liked the submerged bench as well. I have been wondering what it would take to have one like it at my house.

Googling around I found a place that'll ship me quartersawn cedar wood and all the hardware for $6000 and they say that's an easy weekend to put it together. (Apparently the good old-growth straightgrained redwood is prohibitively expensive nowadays, or so this website says - not sure I buy that.)

That seems like a lot of money to me. Would it be crazy to buy some lumber and a tablesaw and try to DIY this? I am fairly competent with tools, but I'm not a carpenter - have helped friends put their decks together - and I don't know that I'd particularly enjoy doing it, apart from saving money. I'm also not a cooper - a redwood hottub is basically half a barrel, as far as I can tell - and I have no idea how it works to make these watertight.

Would this be a normal request to make of someone who puts together redwood decks, that they come and build me a hot tub?

Any advice or thoughts would be appreciated.
posted by Protocols of the Elders of Sockpuppetry to Home & Garden (11 answers total) 4 users marked this as a favorite
 
Hm. My friend built a hot tub once, but it took a bit longer than a weekend and he had a few buddies to help him. It was really crude, not anything meant to be beautiful or even very durable. I'd say you'd need more than one weekend (maybe two or three), but hopefully others with more expertise can chime in.
posted by The Biggest Dreamer at 6:25 PM on May 1, 2013


I don't build things, but quick googling came up with a full how-to PDF on building a wooden hot tub from scratch (with their heating element of course, but you will need to buy one anyway probably.). Evaluate to see if you have all the tools you need.

Basically you need to make sure that you have space, tools -or can buy tools -, lumber, and you may need some people to help.
posted by Crystalinne at 6:26 PM on May 1, 2013


A buddy of mine bought a used redwood tub, disassembled it at the sellers house, and put it back together. It eventually held water again, but there was a lot, LOT of work involved, and a lot of tracing leaks. When he sold it, the next buyer brought a huge truck and took it whole.

Also, old growth redwood is mostly found in national forests these days, so that's not bullshit on the cost.
posted by hwyengr at 6:48 PM on May 1, 2013


If you care more about function than form, I've seen plans for hot tubs using stock tanks.
posted by oceano at 7:00 PM on May 1, 2013 [2 favorites]


How many redwoods have been logged?

96 percent of the original old-growth coast redwoods have been logged.


So that part's not bullshit. There is reclaimed redwood out there on the market (reclaimed from sinker logs, old buildings, etc.), but it's not a lot, and yeah, it's expensive.
posted by rtha at 8:35 PM on May 1, 2013 [1 favorite]


I have assembled a hot tub from a kit like you describe. Assembling it is very hard and in my opinion if you care about the result you'll hire someone who is likely to be very good at this, like a contractor, probably not a deck contractor but maybe. With a hot tub, keeping the tub level with the ground is important, and that's after it has been filled with hundreds of gallons of very heavy water. Just getting the seat inside the hot tub level is hard. Running the PVC to connect the jets to the water source is hard. Installing the heater will require a place to locate it along with the pump (I recommend not right next to the hot tub), and you'll want to run some gas and electricity over there if it isn't there already. You might even need to put concrete down. The hot tub places ship their kits in good faith but if you intend to assemble one, think all the details through.

Okay so your actual question was if you could do the woodwork yourself. Discounting the bench, there are two kinds of wood parts, the vertical planks and the two halves of the circular disk forming the floor. The vertical plants have been cut very precisely with some small detail work which makes them all fit together like a puzzle (they also have a groove which slides around the floor disk halves). They don't just fit together, they fit together after having had steel bands tightened around them (like a wine barrel), and after being continually soaked with water. After assembly, you sand down the surfaces so they are smooth, that part is mercifully easy. I think making the cuts to the wood, if you had the right kind of wood, would not be hard for an amateur to do, if you did it with great and exacting precision. Making a mistake would suck and you might not notice until you had the whole thing assembled. However knowing the exact dimensions and shape to strive for is a challenge not just of geometry but of knowing how wood handles aging and water. That also sounds a little hard to me.
posted by doteatop at 8:55 PM on May 1, 2013 [1 favorite]


Seriously when I was doing this I spent hours just trying to figure out the exact angle the floor should be oriented bearing in mind the orientation of the joints beneath the hot tub, holding it up, the future path of the PVC I would have to run, the possible locations of the floor suction things, man it kills me just trying to remember all those details. I thought it would be easy. Ow.

On the other hand having a hot tub is great, it's a year later, the thing is beautiful and you should get one.
posted by doteatop at 8:58 PM on May 1, 2013


Yeah, dude, seriously, get a 300-gallon stock tank (and sheath the outside in wood if you want it to look pretty). Building a wood hot tub is decidedly NOT a weekend project.
posted by rabbitrabbit at 9:13 PM on May 1, 2013


The ones I've seen built were made with 2x6s with a doubled bottom. Narrower wood gives a more circular shape but also increases the amount of milling you need to do and the amount of expensive cedar that ends up as expensive mulch.

Wood cost: Say a six foot diameter hot tub with sides 4' high giving you maybe 39" of inside water depth. That's 18.84 feet in circumference, call it 19' or 228 inches. Say you make it out of 2x6 material that is 228/5*4 230 BF of cedar for the sides. The bottom is 28+ square feet, call it 30 for waste allowance. Each square foot is 3 board feet so another 90 board feet for the bottom and say a 1/3rd of that for benches and steps give a total of 230+90+30=350 board feet. Allowing for 10% waste gives 380 board feet. Clear western red cedar is somewhere around 2-3 dollars a board foot around here when you can buy it and they cut it all around here. So you're looking at 760-1140 dollars in wood.

Plus three bands of steel, say a couple hundred dollars.

Now your boards will need to be milled twice. once for a groove and then again for a tongue. You can do this with a moldhead in a radial arm or table saw or with a heavy duty router in a table or with a shaper or best but most expensive with a moulding planer. Anything but the last choice is a butt load of physical labour as you are milling nearly 1200 linear feet of 2x material. With a table saw if you have experience, a good saw and are in shape you could probably do just the milling in 10 hours or so or somewhat less if you had some one stacking for you.

Now you have (assuming 8' and 12' material) about 300 cross cuts to make; say another couple of hours.

Then you move on to dadoing the grove for the bottom; only 230 cross cut dados to make (I'd use a router with a jig; my father would use a dado head in a radial arm). Oops that's actually 460 as most dado cutters max out at less than 1.5 inches so two cuts each. Another couple of hours.

Then assemble the bottom and cut the circle twice: 2-4 hours.

You can probably hire out bending the hoops but if not you'll spend a couple hours with a roller set getting them curved.

Final assembly shouldn't take more than a day but you'll need several people to help.

Figure another half day to construct and install benches.

So I'm guessing about 25-30 hours if you are familiar with the work needed and have help at appropriate times. You could do it in a long weekend but I'd probably schedule several weekends (milling that wood is going to be brutal). And budget a couple grand in wood, steel and special tongue and groove cutting tools assuming you have all the rest of the tools already.

You could go tailless too, shouldn't take you more than a couple weeks to mill all those tongues and grooves with a pair of matched planes.

On preview the linked plan shows half round cross section joinery which would work great but can not be done with a moulding head; you'd need a shaper or moulding cutter.
posted by Mitheral at 10:46 PM on May 1, 2013 [1 favorite]


OK, heard enough. This is beyond my capabilities, I think. Thanks for all the replies; each was helpful.
posted by Protocols of the Elders of Sockpuppetry at 12:22 AM on May 2, 2013


Seriously though the cedar hot tubs are beautiful. You can pay for the kit and hire someone to build it all for maybe under 9k (though I recommend getting the higher-powered heater and the biggest tub they have).

If you figure that normally you'd pay ~$40 to visit a hot tub in a guest house or spa-type place, and you get in the hot tub twice a day, the hot tub will have paid for itself within 4 months. It's totally changed my life, I garden and stuff now. I pull weeds for fun. Being out back is awesome whereas before I just had a lawn, now I have like crazy trees and flowers just because I'm using the space more. I also have an alternative to watching MST3K at night and I'm hitting bars a lot less. Twice a day is kind of a minimum— getting up early and having coffee out there is great. I was broke for a while afterwards but I had a good place to try to relax away from the worries.
posted by doteatop at 7:51 AM on May 2, 2013


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