DIY Hot Tub Project (Wood Fired, Cedar)
What if you could build your very own hot tub with locally or store-bought cedar? What if using fairly basic tools you could build your own hot tub that could rival a commercial wood fired cedar hot tub but that doesn’t cost you $6,000+? This project set out to do just that, and achieved the objective quite well. This is a 5-foot hot tub that can seat 3 people comfortably.
The Why Behind the Project
When we first moved to our bare land to build our dream house, we decided that we wanted a hot tub so that we could soak away our sore muscles at the end of the day. Property development while living off grid is a ridiculous amount of work!
We first built a deck from trees on our property using a chainsaw mill. At first we envisioned creating a “cowboy hot tub”. We purchased an 8’ diameter round galvanized tank and quickly after we brought it home we realized it wasn’t what we wanted. We thought “why not built something we love that will last and try our hand at a wood fired cedar tub?”
Cedar hot tubs are expensive if you buy them retail – anywhere from $3,000 to $7,000 depending on the size of the tub and the number of upgrades you choose to have. We did some rough calculations and determined that we should be able to build our own cedar hot tub for pennies in comparison (around $300), so we set out on a journey to try and are more than pleased with the results.
Not only did we successfully build our very own wood fired cedar hot tub but we documented the process so that others could benefit. Check out the entire series here, but we’ll lay out the rough details below!
Step One: Finding Clear Cedar Boards for Pennies
First we began accumulating materials for our diy hot tub except there was one problem we knew we’d have to address right off the bat: Cedar wood can be incredibly expensive and we didn’t have any on our property. We weren’t about to let that stop us and knew there had to be a way.
In the first video in our series we go through some of our tips and tricks for finding high-quality cedar at very low prices, even from wood that at first glance appears to be low-quality.
In short, we found sources of “cedar seconds”, or lower grade cedar that contained a lot of knots. It goes without saying, hot tubs are usually built with knot-free, premium cedar, in fact the highest grade cedar is often an up charge from hot tub manufacturers.
We found a couple of lumber yards that let us “sort” their lumber, meaning we could hand pick the boards we wanted. We found boards that had large areas of clear wood, or knots on only one half of the board that could be cut out. We bought just enough lumber where we thought we could cut out enough knot-free staves. It was very affordable.
Step Two: Cutting the Staves
Now it’s time to turn that wood into staves (narrow wood panels like the side of a barrel) for building the sides of our tub.
We found that cutting wood staves took a lot of creativity for us because we want to reuse as much full-width excess wood as possible for other features like stairs, benches or handrails.
Simply ripping each board in half to pull out the staves would waste a lot of wood. To get the maximum yield, we inspected each board carefully and isolated where the good wood was for each board.
Next, we varied between cutting boards with a cross saw or ripping them in half, depending on where the quality wood was located on each board.
This was a slow, deliberate process but the amount of quality wood we were able to salvage for other projects was well worth the slower pace.
Step Three: The Stave Joinery
There are multiple ways to do this, but this is the way we have found that works best for someone with minimal tools.
This is arguably the most important step in this entire project… if your joinery is bad, the rest of the project will go downhill.
All you need to do the joints are two router bits (bead and cove) and a router to make a canoe joint. This allows you to form the staves into a circle and when the cedar swells with water, it will seal up tight (if you do it properly). Practice, practice, and practice some more before you do the final joinery.
In the bottom of each stave we put a dado joint that would eventually tap onto the floor. We did by running it through a tablesaw several times.
We learned a lot in this process and in the end, yes, our hot tub holds water, but we found many things we’d do differently found in our tips and tricks section at the end of this page.
Step Four: Building the Floor
After gathering cedar wood, building staves for the sides, and creating a proper stave joinery, it’s time to build the floor to our tub!
Commercial hot tub manufacturers typically use 2×6 boards for the floor but we had to work with what we had.
We used 1×6 tongue and groove cedar and it worked, but if we were to build the tub again or give advice we would recommend going with 2×6 boards if possible.
We selected the very best boards and put the very best wood within the diameter of the floor. Once positioned we applied wood glue, strapped everything together, used weighting to prevent the floor from buckling, drew a circle, and then used a jigsaw to cut out the floor (and leave all the knots and bad wood behind as scraps).
In this video in the series we also talk about the ‘magic number’ of stave depth groove and how doing this one simple calculation several times saved us a major headache down the road.
Step Five: Assembly
All the separate pieces have been made so now it’s time to join everything together!
First we gently scraped to excess wood glue off the floor.
We put the floor up on saw horses and planned to build the walls of the tub upside down. We used a trimming off of one of the staves to gently pound the bull nose side of each stave into the floor joints.
We worked with each stave to get them to fit correctly and occasionally switched a few out to find ones that created a better fit. Patience was a virtue here.
But all the patience in the world couldn’t save us from our MAJOR CONUNDRUM!
Somehow our careful math was off and we were left with a half stave gap on the side of our tub. Face palm. Watch the video to see how we resolved this.
We then used airplane cable attached to turnbuckles to tightly secure the tub. We spaced three cables out evenly.
We flipped the tub over and moved it into its final resting location. We placed it off the ground on six 4×4 pieces of treated fir. Our tub was ready to hold water, but not before adding a few accessories.
Step Six: Benches & Plumbing
Next we installed the floor drain and benches into our cedar hot tub.
The benches were built as four sides of a hexagon, and we got to recycle the blemished staves that didn’t make it into our hot tub frame into supports for the benches.
Though our wood costs were minimal, we certainly paid a hefty price for the stainless hardware that we chose to use.
At $.50 to $.75 per screw, the benches cost us close to $44. Thankfully, the benches were a perfect fit.
We installed the floor drain where there were no supports under the floor and attached an extended elbow joint to create a backup drain system.
This is really helpful because we can attach a hose to this joint and water our garden when we drain the tub.
Now that our tub is fully assembled it’s time to see if it holds water.
Step Seven: Filling the Tub
It’s been a long process, but the tub is complete and ready to be filled with water.
Sounds simple, but one big factor made this process exponentially more complicated for us: we live off grid.
All the water we use in the tub has to be brought in, and we initially relied on seven gallon jugs.
We tested for leaks in the tub by pouring in these jugs, but the water leaked out faster than we could fill it, leaving our tub empty and our precious water wasted.
Plan B was to expedite our cistern tank plan and use the power of thousands of gallons of water in one place to quickly fill the tub.
Easy enough, right? It wasn’t. We struggled with our leaking tub for two weeks before it consistently held water! Somewhere in there we added interior caulking as well since we needed all the help we could get although in hindsight we aren’t sure if we needed this or not. You should NOT if your joinery is tight. This was such a tedious process but it was all worth it!
We’ve been losing some on the hottest days (mainly due to evaporation) but beyond that our tub has been watertight.
Step Eight: Installing the Submersible Wood Stove & Fence
Now that our tub was holding water it was time to heat it up. We found a second-hand submersible hot tub stove from a friend of a friend for $250 and got to work.
We have lots of tips on what to look for when buying a stove for a tub, so be sure to check out the video for more information.
We installed the stove by bolting it to the sides with stainless steel bolts (it was so buoyant we needed to use bolts instead of screws to keep it down!)
We also built a quick and dirty fence to put in front of the stove as an added layer of protection.
The stove works and we have been soaking in our warm tub every evening we can.
Step Nine: The First Soak
Finally, it was time to take our tub for a test spin. We lit our first fire, pre-chilled some hard root beer and waited several hours before the tub was at a toasty 100–102 degrees Fahrenheit.
It was everything we imagined and then some. Nothing explains what it’s like to get in your cedar hot tub for the first time and for us, we got to admire our local mountains and look at our future home site, dreaming about the house we would build one day.
We can’t recommend this project enough for those that have the desire to take in on, and the location to make it happen!
Tips & Tricks We Learned
All said and done, we have a large, growing list of tips and tricks that weren’t mentioned in our video series. If someone would have shared these things with us before we embarked on our build, it would have saved us a lot of headaches.
Wood and Staves
- Be sure you have enough wood to have a minimum of 10 extra staves. When doing the joinery on the staves, create many more staves than you’ll need to do the hot tub. If you think you’ll need 60, make at least 70.
- When installing the staves on the floor, if you have two staves that don’t seat really well against one another, take the time to remove the stave and find a stave that fits better. This is well worth your time.
- When using wood glue, be sure not to place wood on wood so as not to glue wood together that shouldn’t be. If possible, use paper or something that will release easily.
- If you use wood glue, especially Gorilla Glue, it WILL expand 3-4 times its size, and it WILL explode out of the joinery, thus gluing itself to anything that is near. Yes, we speak from experience, and we thought we were being pretty conservative on our gluing.
- The amount of love and attention you give to the stave joinery will greatly affect the tub’s ability to hold water quickly.
- When assembling the turnbuckles and cable clamps, place the tail of the cable against the wedge part of the clamp, not the u-bolt part of the clamp. This will make adjusting the cable as needed much easier, because it will slide easily through the u-bolt, but it won’t slide at all through the edge of the cable clamp.
- Don’t forget to place one end of the cable through the eye hook of the turnbuckle before installing the clamps.
- Use firm pressure to force the thimble over the eye hook of the turnbuckle.
- Two people installing the cable clamps makes life a lot easier. If possible, install the cable clamps over somewhere where if you drop the nuts (we did this many times), finding them won’t be like finding a needle in a haystack.
- When installing your turnbuckles, be sure to leave more than enough room to tighten the clamps down multiple times. Every day our tub seemed to shrink in the sun and we had to shorten the cables three times (we ran out of space to tighten the turnbuckles on three occasions, that is).
- Before installing the cables, use three ratchet straps to tighten the tub up. Don’t measure the amount of cable you need until you do this step, and even once you cut the cable, be sure to leave plenty of room to tighten the turnbuckles. We neglected to measure with ratchet straps so all said and done, our cables were far too loose.
Filling the Tub
- To cut down on the amount of water needed to fill the tub, put objects into the hot tub to displace the water
- Be sure to get the tops of the staves wet as this helps them to rapidly soak up water
- If you keep the tub filled for three days and it’s still not sealing properly, you can use some waterproof caulk as a backup plan. Not sure on the longevity of this solution, but it’s better than not using your tub! Be sure to let the caulk cure for the recommended number of days. I think we let ours cure for 5 days (well, we first tried for 24 hours but our caulking failed)
Watch This Entire Series!
Join us for step-by-step videos for this diy hot tub project including lots more information!