I Want to Build a Hot Tub: Where Do I Start? A Step-by-Step Guide

Last updated: September 2026

“I want to build a hot tub, but where do I start?” If that’s you, read on. It’s one of the questions I get asked most, and it’s completely understandable. There’s a lot to think about, and it’s hard to know which decision comes first.

I built my own tub before I really knew what I was doing, and I’ve since helped more than 1,500 people build theirs. This post is the starting point I wish I’d had: the decisions to make, in the order to make them, and the order the build itself goes in.

Step 1: Decide what kind of hot tub you want to build

Before anything else, decide what sort of project this is. A weekend stock tank build and a permanent tiled in-ground tub have almost nothing in common apart from the hot water.

Type	What it involves	Best for
Stock tank	A galvanised livestock tank with a plumbing kit, on a level base	The cheapest proper hot tub, built in a weekend or two
Wooden (cedar)	A timber tub, bought or built, with a plumbing kit	A rustic look, and woodworkers
In-ground block, concrete or ICF	A dig, a reinforced slab, walls, waterproofing, tiles and a control room	A permanent, custom tub of any size or shape
Above ground or raised	The same as in-ground, but built up from a slab with no big dig	High water tables, rock, or easier access to the plumbing

There’s a guide for each: stock tank, wooden, in-ground and above ground. If budget is the main driver, start with What is the cheapest hot tub to build? The rest of this post mostly assumes a permanent block, concrete or ICF tub, because that’s where the planning matters most.

Step 2: Choose the location

The first real decision for a built tub is the location. Quite often there’s an “obvious” spot on your property. Either there’s a place with a view, or there’s only one place you can actually put a tub.

Either way, make sure the location is going to work for you. Think about:

• Orientation. Where does the sun set? What will you look at from the water? What can the neighbours see? See Hot tub privacy ideas.
• Water in. Where’s your water source, and how will you fill it?
• Water out. Where are your drains, for when you want to empty it? See How to drain and clean a hot tub.
• Power. How far is it from your consumer unit (breaker panel)? A long cable run costs more.
• Access for materials. Can a micro digger get in, or will you be digging by hand like I did? Where will the soil go?
• What’s underneath. Buried services, tree roots and a high water table all change the plan.
• The walk from the house. You’ll be doing it in winter in a dressing gown, so keep it short and well lit.

Don’t forget the control room

If you’re building an in-ground or block tub, you need a control room for the pumps, filter, spa pack and heater. On this blog and on my YouTube channel I talk a lot about control room placement and how important it is. Keep it close to the tub, and ideally below the water line so standard hot tub pumps stay primed. And make it bigger than you think you need. I didn’t, and I’ve had to rebuild mine since. See Hot tub control room position and Hot tub control room design considerations.

Step 3: Decide the size and shape

Size and shape are important. Complicated shapes are more difficult to build, and larger tubs take longer to heat up and cost more to run.

Think about the size, and also about the volume of water that’s going to be in it. It’s always a good idea to compare against some of the plastic shell tubs on the market. That gives you an idea of whether you’re about to go “too big”.

To give you a starting point, the most common size my customers build is 8ft x 8ft (about 2.4m x 2.4m) internally. Some go bigger and some go smaller, but it seats a family comfortably without being expensive to heat. Squares and rectangles are far easier for a first build than curves. There’s more on getting the dimensions right in What makes a good DIY hot tub design?, and if space is tight, see A small hot tub for a small backyard.

Step 4: Choose the construction method

The construction method you choose matters. What are your skills? If you’re more of a timber person than a bricklayer, forming and pouring concrete walls might suit you. If you can lay blocks, block is the obvious choice.

Then there’s the slightly “left field” option: ICF (insulated concrete form) blocks like TubBlox. The insulation is already there for you, and the forms go together very easily. ICF has become more and more popular with my customers, and if I built my own tub again, it’s what I’d use. There’s a full comparison in DIY hot tub construction: block, ICF or poured concrete? and The best ICF blocks for building a hot tub.

Whatever you build the walls from, the structure isn’t the finish. It’s structure, then a proper waterproofing membrane, then tiles. See Waterproofing, grout and tile adhesive.

Step 5: Plan the electrics

A hot tub needs its own dedicated circuit, separate from everything else in the house, with earth-leakage protection to guard against electric shock. What that looks like depends on where you live.

• UK: Houses have a 230V single-phase supply. A built tub with a full spa pack usually needs a dedicated circuit (often 32A, depending on the pack) from the consumer unit, protected by a 30mA RCD (an RCBO is the neatest option), with a local isolator. It’s notifiable work under Part P, so use a registered electrician who can certify it.
• USA: People often tell me they don’t have 240V. You do. Most homes get a split-phase supply: two 120V “legs” (L1 and L2) plus a neutral. Between the two legs you get 240V, which is what an electric range or dryer uses. A spa pack is wired across L1 and L2, typically on a dedicated GFCI-protected circuit (50A is common, but it depends on the pack), with a disconnect within sight of the tub. Your electrician sizes it, and it usually needs a permit and inspection.

Why the higher voltage? For the same power, doubling the voltage halves the current. That means a sensible cable size, and it lets the heater and pumps run at the same time without tripping. The full details are in A guide to hot tub electrics and Hot tub wiring explained.

Step 6: Choose how you’ll heat it

The heating method is one of your most important decisions, because it drives the plumbing, the electrics and your running costs. The main options are:

Heating	Pros	Cons
Electric (in the spa pack)	Built into pretty much every spa pack, simple and cheap to fit	Slow on a big DIY tub, and the most expensive to run
Air source heat pump	The cheapest to run: typically 3 to 7 units of heat per unit of electricity	Higher upfront cost, and less efficient in cold weather
Gas or propane	The fastest heat-up, whatever the weather	Running costs depend on your gas price, and it needs a qualified gas installer
Wood-fired	Rustic, and works off-grid	Labour-intensive, and hard to hold a steady temperature
Solar	Free heat once installed	Weather-dependent, so usually a top-up rather than the main heat source

An air source heat pump is certainly my favourite option. It takes heat from the outside air and moves it into the water, using electricity only to run the compressor and fan. The US Department of Energy puts pool heat pumps at a COP of 3 to 7, and says they work best when the air is above about 45–50°F (7–10°C). They still work in colder weather, just less efficiently, so size the unit for your tub and your climate. When I fitted one to my own tub, I cut my running costs by 66%.

There’s more in What is the best method to heat my DIY hot tub?, The ultimate guide to air source heat pumps for hot tubs and How to choose the right air source heat pump.

Step 7: Jets, water features and extras

Decide on jets, lighting and water features now, not later. You can add a waterfall, a water blade, a fountain or lights, but you need to think carefully about what you’re adding and how, because each one affects the plumbing and the electrics.

• Jets: as a rule of thumb, one jet pump runs up to about 16 jets. More than that needs a second pump. See How many pumps do you need?
• Water features always need their own pump and suction. Tee one off the jets and one will starve the other. See Adding a water feature to your DIY hot tub.
• Lights need their conduit and niches in the wall before it’s filled with concrete. See The ultimate guide to hot tub lights.

None of these are things you want to bolt on afterwards.

Step 8: Check permissions and buried services

• UK: The Planning Portal says you typically won’t need planning permission for a garden hot tub, unless you’re in a listed building or a conservation area. The electrics still have to meet Building Regulations. Before you dig, run a free search on LinesearchbeforeUdig.
• USA: Many cities and counties want a permit for an in-ground spa, and some require a barrier or a lockable safety cover. Call 811 a few days before you dig so the utilities can mark their lines. See Do I need a permit for my hot tub?

Step 9: Be honest about time and budget

A block or ICF tub is weeks to months of evenings and weekends, with curing times you can’t rush. For a real-world picture, read How long does a DIY hot tub build take? For costs, What are the pros and cons of building a hot tub? compares DIY with buying. If you’re still deciding whether to build at all, my own reasons are in Why build a hot tub when I can buy one?

The build, in order

Once the decisions are made, a typical in-ground build goes in this order:

1. Plans and design. Every dimension, plumbing route and parts list worked out.
2. Permissions and buried services checked.
3. Set out and dig, deeper than the water depth to allow for the layers underneath. See DIY in-ground hot tub build guide.
4. Sub-base, main drains, hydrostatic relief valve and a reinforced slab.
5. Walls and seats in block, ICF or poured concrete, with the plumbing through the walls set before they’re filled.
6. Plumbing glued up and pressure tested before anything gets buried. See DIY hot tub plumbing.
7. Render, waterproofing membrane and a flood test.
8. Tiles and coping.
9. Control room kit (pumps, filter, spa pack, heater), then the electrical supply by a qualified electrician.
10. Fill, balance the water and heat it up. See How to fill a hot tub the correct way.

Common mistakes when starting out

• Digging before there’s a plan. The hole depends on the design, not the other way round.
• Going too big and then paying to heat it.
• A control room that’s too small or too far from the tub.
• Leaving the heating and electrics until the end, then finding the supply or the pipework won’t suit.
• Adding water features as an afterthought.
• Skipping the flood test and finding a leak behind finished tiles.

There are more in Avoid these 7 DIY hot tub mistakes and Planning a DIY hot tub: 10 key decisions to make before you dig.

The easiest place to start: a proven plan

My plans are a great way to get started with your DIY hot tub. My DIY hot tub plans come in a range of sizes, in imperial or metric. Each one has CAD drawings with every dimension, multiple plumbing layouts, a full parts list, access to my video course and the Ultimate DIY Guide. There’s a huge amount of value in them, and they answer most of the questions above before you’ve picked up a spade.

If your space or ideas don’t fit a standard size, sketch your layout in the free Tub & Pool Designer Pro software, and I can turn it into architectural CAD and a 3D plumbing design. For something fully bespoke, there’s my custom hot tub design consultancy. On a tight budget, the complete stock tank hot tub plumbing kit is the quickest way to a proper hot tub.

FAQs

What’s the first step in building a hot tub?

Decide what kind of tub you’re building (stock tank, wooden or in-ground), then pick the location and plan the control room alongside it. Get a design or plans before you dig.

What size should my first DIY hot tub be?

The most common size my customers build is 8ft x 8ft (about 2.4m x 2.4m) internally. It seats a family without being expensive to heat. A square or rectangle is much easier to build than a curved shape.

Do I need a 240V supply for a hot tub in the USA?

For a built tub with a full spa pack, yes, usually on a dedicated GFCI-protected circuit. Most US homes already have 240V available across the two legs of a split-phase supply. An electrician will size the circuit for your pack.

What’s the cheapest way to heat a DIY hot tub?

To run, an air source heat pump. Gas is the fastest, and electric through the spa pack is the simplest to install but the most expensive to run on a big tub.

Can I build a hot tub with no building experience?

Yes. Plenty of first-timers have done it. You need patience, basic concreting and blockwork, PVC pipe gluing and a good set of plans. Leave the electrical supply to a qualified electrician.

Not sure where to start with yours? Tell me about your space and plans in the comments below. I read them all.

Cheers,
Andi

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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