Hot tubs are a wonderful luxury to have in your home and wooden hot tubs provide genuine aesthetic value in the right setting. They are very expensive to construct, however, which may be enough to give some enthusiasts pause. Serious carpenters and those with a good knowledge of water systems can build their own wooden hot tubs over the course of a few days. The project requires wood of the proper type (cedar or teak is best) as well as hot tub supplies found at any pool store or do-it-yourself hardware store.
Select a location for your hot tub. It needs to be somewhere sheltered from the wind and able to support the weight of both the tub and anyone in it. Look for a porch or a concrete landing at least 3 1/2 inches thick to place it on, or else it may sink. In addition, the surrounding ground needs to be as level as possible for the hot tub to work as it should.
Lay down a trio of chine joists evenly on the measured location for your hot tub. Two of the joists should be on either end of the measured area, while the third should be exactly in the middle. The lengths of the joists will depend on the size of your tub; for a four-person tub, the side joists should be 2 1/2 to 3 feet long and the centre joist should be about 5 feet long.
Lay down the bottom of the wooden tub along the joists. Use a piece of cedar or similar wood cut to the size you desire and fitted with holes for the pumps and suction. Make sure the joists do not cover any of the holes. Secure the bottom in place using dowel pins. You can also use heavy nails or bolts, but you need to make sure they are absolutely flush with the tub bottom. Otherwise, you risk stubbing your toe on them when using the tub.
Install suction fittings into the two holes in the bottom using a screwdriver. Keep the screws tight, but not too tight. If you over-tighten, then the fittings may start to leak when the wood swells.
Position a series of wooden tub staves along the length of the tub bottom until they are fitted into place. Check the seams between them to make sure they are tightened, and note the location of the skimmer hole in one of the staves (it will be the one bigger than the jet holes). You should place that reasonably close to the suction holes if possible. Then slide a pair of tub bands over the entire assembly and tighten them into place. The bands should be placed anywhere between 18 and 30 inches from the top of the tub, and 18 and 30 inches from the bottom of the tub.
Hold the bands in place by pounding 4 to 6 nails directly above and below them (16 to 24 nails in all). The nails should be spaced equidistant around the circumference of the tub. Check the tub interior to make sure none of the nails are poking through.
Add epoxy sealant to all of the seams between the planks of wood. Make sure there are no gaps in the sealant and wait 24 hours for it to dry.
Measure a series of wooden planks to be used for the benches and cut them to fit the size of your tub. You'll need to use 2-by-4s to support them, also cut to the appropriate size. The benches should be no deeper than 26 inches below your intended water line. The 2-by-4s should be 1 1/2 inches shorter than that mark.
Fit the 2-by-4s in place and secure them to the sides of the tub with bolts. You should have between 8 and 12 2-by-4s in order to provide adequate support around the whole tub. Make sure that they do not cover any of the jet holes, and that the bolts are long enough to reach into the sides of the tub but not long enough to poke through, or the tub will leak at the bolt holes.
Mount the bench planks on top of the 2-by-4s and secure them in place with bolts or screws. As with other aspects of the hot tub, you want the bolts or screws to be absolutely flush with the wood.
Attach the tub skimmer into its allotted hole and secure it to the sides of the tub with screws. You may wish to apply epoxy sealant around the edges to prevent leaks.
Run PVC piping from the skimmer and suction fittings to a length of larger 2-inch piping. Apply PVC sealant to the connections to keep them from leaking.
Attach hot tub jets to each of their allotted holes and tighten them into place with bolts or screws. There should be 12 to 24 jets spaced equidistant around your hot tub. High speed jets will be placed on the higher holes and will only be used when the hot tub is operational. Lower speed jets (of which there should be about half as many as the high speed jets) are placed lower and will be used to circulate the water when the tub is not in use.
Install PVC piping onto "T" lengths and connect them to the external attachments of the jets. Use sealant on the connections to make them waterproof. You'll want to connect the pipes together before you connect the "T" fittings to the jets, or you'll never fit the pipes into the "T" fittings.
Connect the low speed jets, the pump lines and the skimmer to a 3/4 hp water pump with PVC piping. Connect the high speed jets to a 2hp water pump in the same manner. Apply sealant to the piping connections to prevent leaks.
Connect the output of the 3/4 hp water pump to a water filter and a heater with PVC piping. The piping should fit right into place on all elements, and you can apply sealant to help prevent leaks as with earlier steps.
Add a line of PVC piping leading away from the filter and the indicated opening and connect a thermowell to it. This will regulate the water temperature.
Connect the wires of a timer and control box to the 3/4 hp water pump. The timer will allow you to periodically regulate the water and keep it from stagnating.
Fill the hot tub with water. Turn on the heater, the filter and the 2hp pump whenever you intend to use it, and let them run for several minutes to let the water heat up.
In some cases, you may be able to buy a pre-manufactured wooden tub--recommended for anyone but a serious carpenter--in which case Steps 5 and 6 and Steps 8 through 10 are unnecessary. You will need to get approval from your local building inspector before building a wooden hot tub. Your hot tub needs to meet safety codes specific to your region and conform to any local building ordinances as well. Make sure you have all of the proper permissions before building a wooden hot tub. Wooden hot tubs often leak when they are first used. Eventually, the wood will swell slightly, creating a tighter bond and eliminating the leaks. Try to assemble your hot tub in the spring and summer, when the weather is warm. Cold weather can adversely affect the process (lengthening the drying time of the epoxy, for instance).