How to Build the Ultimate DIY Wooden Hot Tub

Last updated: September 2026

Building your own wooden hot tub is arguably one of the great DIY projects. It takes skill and attention to detail, but the end result is fantastic. There’s nothing more satisfying than sitting in a hot tub you made yourself.

If you’re a regular reader, you’ll know I built my own hot tub, not out of wood but from blocks and concrete. You can read about that in my DIY in-ground hot tub build guide. In this post I’ve pulled together what I’ve learned about wooden tubs, added my own hot tub plumbing knowledge, and come up with my version of the ultimate DIY wooden hot tub.

Wooden hot tub design considerations

The design questions for a wooden hot tub are really no different from any other hot tub:

• Where will it go? Think about access, privacy, the view, and the route for power and water.
• What will it sit on? Water is heavy. Even a medium round tub holds around 1,800 litres (about 480 US gallons), and one manufacturer quotes 4,400lb (about 2 tonnes) for a 65in tub when full. You need a flat, solid base. See my guide to hot tub bases.
• How many people will use it? That sets the diameter and the seating.
• How will you heat it? This is the key one.

The worst thing you can do is design something too big to ever get up to temperature. At one point I thought that was going to happen on my own build. Thankfully I had the guidance of “pool man John”, who reined in my size expectations. That’s advice I now pass on to my own clients. Yes, you can have a big hot tub, but you need to plan and design it so you can actually heat it.

How long will it take to heat?

Here’s a quick way to check. Water needs about 4.19 kJ per kg per °C, which works out to roughly 1.16kWh to warm 1,000 litres by 1°C. So heating an 1,800-litre tub from 10°C to 38°C (50°F to 100°F) takes about 59kWh before any heat losses:

Heater	Rough time to heat 1,800 litres by 28°C (no losses)
3kW electric (typical UK/European spa pack heater)	about 20 hours
5.5kW electric (common on US spa packs)	about 11 hours
Wood-fired (around 9kW for a Chofu) or gas (30kW-plus)	about 2–7 hours

Real life is slower, because a wooden tub loses heat through the walls and the surface. A good insulated cover makes a huge difference. See How to make a DIY hot tub cover.

What wood should I use for a DIY hot tub?

The wood has to cope with being wet on one side, weathered on the other, and warm all year. Here’s how the common options compare. The durability classes are from the European standard EN 350, where Class 1 is very durable and Class 5 is not durable, as summarised by GreenSpec and Woodworkers UK.

Timber	Durability (EN 350)	My take
Western red cedar (North American)	Class 2 (durable). UK-grown is Class 3.	The best choice. Light, stable, swells well and looks beautiful. Clear grades are expensive.
Thermally modified wood (e.g. Thermowood)	Improved by the heat treatment	Very popular in European-made tubs. Stable and rot-resistant, with no resin.
Larch	Class 3 (European) to 4 (Japanese)	A good-value alternative, especially Siberian larch. Resinous.
Oak	Class 2 (European)	Durable, but heavy, hard to machine and pricey.
Spruce / pine	Class 4–5	Cheap but rots unless protected. Fine for cladding a lined tub, not for staves.
Beech	Class 5 (not durable)	Avoid for anything that stays wet.

Cedar

Cedar is a beautiful timber and my favourite. I made my own decking from it. For a hot tub it has to be western red cedar, and ideally clear (knot-free). Knots can loosen and blow out, causing a major leak, and one manufacturer notes that knots cause warping and leaks over time. The same maker says cedar’s natural oils protect it from rot and that it expands well when wet to form a watertight seal.

The hard part is finding an affordable source of clear cedar. Many timber merchants don’t stock it, so ring around and look for one that will let you pick your own boards.

Larch, oak, beech and pine

Larch and thermally modified wood are genuinely good budget alternatives. Oak is durable but usually isn’t cheaper. Beech is rated not durable and I wouldn’t use it at all, and pine or spruce only really works as cladding around a lined tub.

How do I make a round (cylindrical) wooden hot tub?

A round tub is built from vertical boards called staves, sitting in a groove around a round floor, like a barrel. To get the staves to form a circle and seal, you use bead and cove (or tongue and groove) joints cut with a router table and matched router bits.

This isn’t a job for a first-time woodworker. If you’ve shelled out on expensive clear cedar and get it wrong, it makes for very expensive firewood.

The staves are then held together with bands around the outside. Traditionally that’s a vinyl-coated cable (3/16in) with two clamp sets per cable and a stainless steel turnbuckle to tension it, or flat stainless steel straps. Commercial cedar tubs use 304-grade stainless steel straps and screws to avoid rust.

Why does a wooden hot tub leak when first filled?

Your tub will leak the first time you fill it. That’s completely normal. The timber absorbs water and swells until the joints close up, which can take a few days. Manufacturers advise giving it a few days to reach full saturation before worrying. Some suggest filling gradually, about 10cm at a time, to let the wood take up water evenly.

The flip side is that if you leave it empty in the sun, the wood shrinks and it will leak again. Keep it full, or refill it slowly if it has dried out.

Do I need a round hot tub?

Absolutely not. The ultimate wooden hot tub doesn’t have to be cylindrical. It’s actually easier to build a square or rectangular one. There’s still skill involved, but far less specialist joinery.

The tub below was built by one of my customers, Brandon, in the USA. He originally set out to build a stock tank hot tub but couldn’t find the tank he wanted, so he made one out of wood instead.

How do you waterproof a wooden hot tub?

There are two main approaches:

• Self-sealing staves (round tubs). The joints are designed so that when the wood absorbs water, it swells and the joints become tight enough to be watertight. Don’t paint, varnish or seal the inside, because the wood needs to be able to swell. Guidance for wooden tubs is to never treat the interior with sealants and to oil only the outside.
• A liner or moulded insert inside a wooden shell (square or round). This is the route Brandon chose. The insert holds the water and the timber is the structure and the look. Be careful with standard pool liners, though: most are only rated to around 30–35°C, well below hot tub temperatures, so check the rating or use a spa-rated insert. There’s more in Can I use a liner on my DIY hot tub?

A lined tub also avoids some of the downsides of bare wood: you don’t have to keep it full, and the sanitiser isn’t in contact with the timber. One cedar tub maker notes that overusing sanitiser can degrade the wood, so keep your chemistry in range. See The ultimate guide to balancing chemicals in your hot tub.

How will I heat my DIY wooden hot tub?

Wood-fired

You can’t argue that wood-fired hot tubs look cool, and they won’t cost a fortune to run. There are three types:

• Internal stoves sit in the tub with you, with the fire on the other side of a metal wall and usually a guard to stop you touching it. They take up space where another person could sit.
• External heaters sit outside the tub and circulate water through it. If I were building one, this is the style I’d choose. A well-known example is the Chofu, which its US dealer describes as an external stainless steel heater averaging 32,000 BTU (about 9kW) that circulates water by thermosiphon, so it needs no pump or electricity.
• “Cooking pot” tubs sit directly over a fire. I just don’t like the idea. It looks to me more like a witch’s pot cooking a human than a hot tub. Each to their own!

Safety with wood heaters: never light one with the tub empty, keep water well above the stove surface, and never leave a fire unattended. That’s also the guidance from wooden tub makers. If you want to go fully off grid, see my off-grid wood-fired hot tub review

Propane or natural gas

Gas heaters are nothing new in the swimming pool world, and they’re more suited to pools because of the power they can put out. To give you an idea, my own hot tub heater is 3kW. In the USA I design systems around 5kW heaters. Gas pool heaters are commonly several times more powerful, 30kW and up.

The catch is the gas supply. In the UK, gas work must legally be carried out by an engineer working for a Gas Safe registered business, and in the USA it will need a licensed installer and usually a permit. Depending on where the tub sits, that can get expensive. There’s more in Everything you need to know about hot tub gas heaters.

Electric (and heat pumps)

Call me predictable, but this is what I’d choose. Yes, a straight electric heater costs more to run, but it’s reliable and predictable, and there’s less hassle. The idea of building a fire and then waiting for the tub to heat up before I can use it seems like too much hard work to me. Set the temperature on the control panel and let technology do the rest.

Air source heat pumps are the way I’d cut the running costs of any hot tub, and they pair perfectly with an electric spa pack. See What is the best method to heat my DIY hot tub? and my guide to air source heat pumps for hot tubs.

Whatever you choose, the electrics must be done properly: a dedicated circuit with RCD protection in the UK, or GFCI protection in the USA. See A guide to hot tub electrics.

Do I need jets and a filter in a wooden hot tub?

Traditional wood-fired tubs usually have no jets and often no filter. In my mind, that makes them more like a bath than a hot tub. If you don’t have a filter and pump, you have to empty it after every use or two. For something much bigger than a domestic bath, that’s a waste of water, and you’re heating a large body of water just to throw it away.

If you filter the water, sanitise it, and don’t change it every time you use it, that’s a proper hot tub. So when I designed the ultimate DIY wooden hot tub, it had to have jets, a filter and a pump, exactly as if I were designing a stock tank hot tub or a concrete tub. The parts are slightly different, but the plumbing principles are the same. If you’re new to them, start with How does hot tub plumbing work? and DIY hot tub jets: everything you need to know.

So, to answer the question: yes. In my opinion, a proper wooden hot tub needs jets and a filter.

What is the ultimate DIY wooden hot tub?

In my mind, it’s a cedar tub combined with the mod cons: jets, a filter, a two-speed pump, an electric heater and an air blower. It looks something like this:

Complete cedar/wood hot tub plumbing kits

You build (or buy) the tub. I’ll give you the rest. My COMPLETE Cedar/Wood Hot Tub Plumbing Kits are designed for wooden tubs. The 8-jet kit, for example, includes a two-speed pump, a Balboa spa pack, a 25 sq ft filter, an air blower, the jets, drains, valves, unions and a topside control, plus my plumbing guide. The US kits use a 4kW Balboa spa pack, and the European standard is 3kW. Just add a tub and pipe.

• COMPLETE Cedar/Wood Hot Tub Plumbing Kit (4 jets): ideal for smaller round tubs.
• COMPLETE Cedar/Wood Hot Tub Plumbing Kit (8 jets): my pick for a typical family tub.
• COMPLETE Cedar/Wood Hot Tub Plumbing Kit (16 jets): for bigger tubs and more massage.
• COMPLETE Cedar/Wood Hot Tub Kit (heating and filtration only, no jets): warm, clean water without the bubbles.

Building a round cedar tub: the steps

Whether you build from scratch or use a pre-milled tub kit from a cooperage, the order is much the same. It’s a two-person job, so rope in a friend.

Step 1: Prepare the ground

You need a solid, flat base that can take the full weight. A concrete slab, paving flags on a compacted sub-base or a gravel base inside a timber frame can all work. The rule is that it’s flat and can take the full weight of the tub, water and bathers, which is well over a tonne (see the size table below). See How to build a concrete hot tub pad.

Step 2: Position the floor and joists

The tub sits on joists under a round floor. Put it exactly where it will stay, because the tub is heavy once assembled and you won’t want to move it.

Step 3: Fit the staves

The staves are tapped into the floor groove, one by one, with a rubber mallet. Get the angles right and they’ll lock together. Then fit the bands or cables and tension them evenly.

Step 4: Fit the seats

Seats are screwed to cleats on the staves. Two levels of seating work well: a lower seat for a deep soak and an upper one that’s easier for kids and makes getting in easier. If the tub is tall, plan a step outside too.

Step 5: Install the plumbing

Drill the holes for the jets and drains (on my kits that’s 65mm/2.56in for the jets and 85mm/3.35in for the drains), fit the jet bodies and drains with their gaskets, then glue up the pipework to the pump, filter and spa pack following the plumbing diagram. Use proper PVC solvent weld joints and pressure test before you fill.

Step 6: Fill, wait for it to swell, and enjoy

Fill slowly, expect a few days of weeping while it swells, then balance the water and heat it up. Wooden tubs simply have so much more character than plastic shell tubs. If you choose wood-firing, you can even be completely off grid.

How big should it be?

As an example, here are the sizes offered by one US maker of classic round cedar tubs. They’re all 48in high with nearly 43in of interior depth:

Diameter	Max users	Water	Full weight
56in (1.42m)	4	1,334 litres (352 US gal)	3,300lb (1.5 tonnes)
65in (1.65m)	6	1,819 litres (480 US gal)	4,400lb (2.0 tonnes)
74in (1.88m)	8	2,378 litres (628 US gal)	5,750lb (2.6 tonnes)
84in (2.13m)	10	3,124 litres (825 US gal)	7,700lb (3.5 tonnes)

Those full weights are why the base matters so much.

Common mistakes with wooden hot tubs

• Using knotty or non-durable timber for the staves.
• Designing a tub too big for the heater you can realistically run.
• Sealing or varnishing the inside of a stave tub, which stops it swelling.
• Panicking about first-fill leaks instead of giving it a few days.
• Letting a stave tub sit empty and dry out in summer.
• Lighting a wood stove with no water in the tub.
• No filter and no cover, so you’re forever emptying it and reheating.
• Skipping a proper base.

If you love the idea of wood but want something permanent and lower maintenance, have a read of Out with the cedar, in with an ICF in-ground hot tub.

FAQs

What is the best wood for a hot tub?

Clear (knot-free) western red cedar. It’s durable, stable and swells to seal. Thermally modified wood and larch are good alternatives.

Do wooden hot tubs leak?

Stave tubs weep when first filled or after drying out, until the wood swells and the joints close. That usually takes a few days. A persistent leak after that points to a faulty stave, a knot or a plumbing fitting.

How long does a wooden hot tub last?

It depends on the timber and how well it’s looked after. Wooden tub makers quote from 10–15 years to 20 years or more for well-maintained tubs. Keep it full, keep the chemistry balanced and oil the outside.

Can I put jets in a wooden hot tub?

Yes. You need jets and drains designed for wooden tub wall thicknesses, fitted with the right gaskets. My complete cedar/wood plumbing kits include them.

Should I treat the inside of a wooden hot tub?

No. Leave the inside bare so the wood can swell and seal. Oil or stain the outside only.

Can I heat a wooden hot tub with electricity?

Yes. An electric spa pack is the simplest, most controllable option, and adding an air source heat pump brings the running costs right down.

Are you building a wooden hot tub? Share your progress and questions in the comments below. I read them all.

Cheers,
Andi

You can also find me on my socials;

Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi

 

Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Fast forward to 2025, I've helped over 1400+ DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi