If you’re into DIYs and self-care, building your own home sauna is the perfect next project. You could have your own sauna in your house, and the rewarding thing about it is that you built it with your own hands. Exciting, right?
Now, a DIY sauna might sound like something best left to spa designers and professionals, but it’s a project you can actually do easily if you know the necessities. Whether you’re dreaming of a cosy indoor retreat or a rustic cabin-style setup in the garden, learning how to build a sauna from scratch is one of those projects that feels both practical and rewarding.
Of course, it does take some planning. From choosing the right type of sauna to sorting ventilation, insulation, and heating systems, a bit of research upfront saves a lot of stress later. In this guide, I’ll walk you through everything you need to know to build a sauna that looks beautiful, works safely, and feels incredible to step into!
How to Build A Sauna: Pre-Build Planning & Considerations
Okay, let’s start planning our DIY sauna project. There are certain factors you need to consider before actually starting to build your own sauna. Planning them ahead will make your project stress-free and enjoyable. Let’s get into it:
The Right Location
Your first call: Do you want a home sauna or an outdoor sauna?
A home or indoor sauna means year-round comfort and easy access to power and water. Aim for at least 2m x 2m with a 2.1m ceiling, and plan for good ventilation and moisture protection. Usually, basements, bathrooms, and utility rooms are good spots.
An outdoor sauna brings that cabin-in-the-garden feeling, a peaceful escape just steps away. You’ll need a flat base, and access to electricity and drainage if you want lighting or a shower. Keep it close enough for comfort but far enough for airflow and privacy.
Planning Permission Sauna
Important question: Do you need permissions?
Before you start, you need to know what the sauna building regulations UK are. In the UK, most outdoor saunas are classed as permitted development, so you usually won’t need planning permission. Just stay within limits, around 2.5m high for flat roofs or 4m for pitched ones, and not right up against boundaries.
If you live in a conservation area or plan to use a wood-burning heater, check with your local council first. Some regions restrict burners in smoke control zones, so it’s better to confirm early. Other than that, you’re good to go!
Budget-Friendly Project
Final bit: A clear budget helps everything fall into place.
Okay, let’s talk money. A DIY sauna kit can cost between £900 and £3,000, while a custom build typically ranges from £3,000 to £10,000+. DIY sauna gives you creative control and savings, while buying a pre-built one means expert insulation and safety from day one.
Now, I have a suggestion for you. If you want a home sauna or an outdoor sauna that’s sleek in design, functional in purpose, budget-friendly, and fun to assemble, you can get yours from Polar Recovery. These saunas are practical and very easy to install, thanks to their clear instructions. You can basically assemble them in 10 minutes. You won’t build from scratch, and will not break the bank.
Now that you know how to plan ahead, you can get to the fun part! Whichever route you choose, thoughtful planning now means less stress later and more time enjoying the heat.
Essential Design Decisions
Fun part in how to build a sauna? Making design decisions! It’s time to visualize your sauna now. The design phase is where comfort, performance, and personality come together. Plus, you need to make decisions on the type of heater or ventilation you want. Here you can find a complete list of sauna materials you need:
Choosing Sauna Heater Type
How to build a sauna that’s effective? The most important decision you have to make is choosing the right heater type. This is what you build your own sauna around. Let’s take a brief look at sauna heater types and what they are suitable for:
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Electric Heaters: Clean, quick to heat, and easy to control. Good for home saunas. Check your power setup: small units usually need single-phase, larger units may require three-phase.
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Wood-Burning Heaters: The classic Finnish style sauna. Perfect for an off-grid or outdoor sauna, but needs proper ventilation and may be subject to smoke control rules.
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Infrared Heaters: Heat your body directly rather than the air, working at lower temperatures. Ideal for a gentle, energy-efficient experience and available in our home sauna range.
Tip: To size your heater, calculate your sauna’s volume (L × W × H) and allow roughly 1 kW per cubic metre. Add a bit more if you have glass panels: +1 kW per m² single-glass, +0.5 kW per m² double-glass.
Selecting Wood & Materials
The most exciting part of building your own sauna is choosing the look! For that, you’ll need to figure out what sauna materials you have to use. Now, the best wood for sauna makes all the difference in both look and comfort:
- Hemlock: Smooth, stable, and low-maintenance. Gives a clean, modern look.
- Cedar: Aromatic and moisture-resistant. Stays cool to the touch.
- Spruce: Strong, light-toned, and cost-effective.
- Aspen: Soft, heat-resistant, and gentle on the skin.
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Alder: Durable, warm-coloured, and naturally smooth.
One tip I can give you is to avoid treated construction timber or plywood because they release fumes when heated. We won’t want that!
Sauna Ventilation System
For sauna ventilation, you need to know that it’s not optional because this is exactly what keeps your sauna safe and comfortable, especially if you’re opting for a wood-burning heater.
You’ll need an intake vent near the heater, an exhaust vent on the opposite wall, and preferably, a small gap under the door to keep the air circulation going. This whole system allows six air changes per hour and helps maintain oxygen levels in your DIY sauna and prevent overheating.
Interior Layout & Ergonomics
Another cool design choice is your sauna layout! Typically, you can use two-tier benches, about 1050mm for the upper, 600mm for the lower, and a 300mm step between them.
Also, consider that the sauna door must open outward for safety reasons. You can use a glass door for a more modern look, or go for wood for a more traditional finish.
You can also add windows if you like, especially for outdoor saunas to create a cozy cabin look, but ensure they are minimal and double-glazed, as windows can increase heat loss.
To wrap it up, add heat-resistant and moisture-proof lighting to create that warm, calming glow in your sauna sanctuary!
Electrical Requirements
Unless you’re a qualified electrician, hire a professional for electrical requirements. As you know, electricity and heat don’t really go hand in hand, so you’ll need to be very cautious. In the UK wiring regulations, saunas are classed as “special location,” which means standard rules don’t apply. So in terms of regulations again, you’re good to go.
Your system will need RCD protection and heat-rated cables such as H07RN-F rubberised or SiHF silicone, which can withstand high temperatures. Make sure the control panel and thermostat are installed outside or in a cooler, accessible spot to prevent overheating and ensure accurate readings.
I’ve mentioned this before: if you’re using an electric heater, check whether your model requires single-phase or three-phase power. Your electrician can help you with wiring and breaker capacity, keeping everything safe and compliant.
How to Build A Sauna: Step-by-Step Construction
Let’s get serious now. I’ve provided a step-by-step manual for you here. These steps should cover most standard DIY sauna kits, but do read the manufacturer instructions that come with yours. Mainly, I want to show you here that it’s really not that hard to build your own sauna when you follow the manual.
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Frame the room: Build studwork, check everything is perfectly level and plumb. Sketch positions for vents, heater, and benches before fixing studs.
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Rough electrical: Run cables only to the point required and leave final connections for a qualified electrician.
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Ventilation routes: Cut holes and route ducts for intake, exhaust, and optional drying vent; position intake near the heater and exhaust opposite.
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Fire-rated plasterboard: Apply where required by local regs (e.g., between sauna and dwelling) for added fire protection.
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Insulate and vapour-seal: Fit mineral wool or specialist sauna PIR/foil boards, then install a continuous vapour barrier behind cladding to stop moisture damage.
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Fix battens: Battens create the ventilation cavity behind timber cladding and give you fixing points for benches and panels.
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Second-fix electrics: Electrician returns to install switches, isolators, and final cable terminations; always use high-temperature wiring where specified.
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Clad ceiling first, then walls: Tongue-and-groove or sauna boards; ceiling first avoids damage during wall work.
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Install ventilation covers and door: Fit adjustable vents and an outward-opening door (glazed or timber to taste).
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Build and fit benches: Install two-tier benches if following classic ergonomics; secure tightly.
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Fit lighting and decorative finishes: Choose moisture-proof, heat-rated fixtures.
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Heater installation & final checks: Have a professional install and commission the heater; run final inspections, test ventilation and electrical certs, then clean and enjoy.
Common Mistakes to Avoid in UK Sauna Building
You can’t learn how to build a sauna without knowing the mistakes to avoid. Here’s what to watch out for:
- Poor ventilation: Without airflow, heat and oxygen levels suffer. Plan intake and exhaust vents early.
- Undersized heater: Always match heater power to your sauna’s volume and glass area.
- Wrong sauna insulation: Avoid standard PIR boards, they can off-gas. Use mineral wool or sauna-rated boards instead.
- No drainage: Add a gentle floor slope or small drain to manage condensation.
- Unsafe setup: Use heat-rated cables and a fireboard behind the heater.
- Too much glass: Keep glass to a minimum or boost heater capacity.
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Skipping drying: Leave vents open after use to prevent moisture damage.
Avoid these early, and your sauna will reward you with years of flawless, toasty performance!
How to Build A Sauna: A Wrap Up
You now know how to build a sauna. This DIY sauna project is not just possible, but is extremely rewarding. Just make sure you plan ahead, watch out for mistakes, and follow instructions religiously.
If you want this project to be easy and end in a beautiful sauna, invest in a Polar Recovery sauna. Our infrared sauna is easy to assemble, efficient in functionality, beautifully designed, and also budget-friendly.
Whether you go full DIY or mix in expert help, the reward is the same: a peaceful, revitalizing space you built for yourself.
FAQ
Do I need planning permission to build a sauna in the UK?
For indoor saunas, usually not, especially if you’re installing a prefabricated kit. Outdoor saunas often fall under permitted development, but it’s always best to confirm with your local authority, particularly if you live in a conservation area.
How much does it cost to build a sauna?
DIY kits start around £900, quality outdoor builds range from £3,000 to £8,000, and full custom designs can exceed £5,000, depending on size and materials. With Polar Recovery, you can get an indoor sauna between £2,499 and £3,499 and an outdoor sauna between £4,299 and £4,999, depending on size.
What’s the ideal size for a home sauna?
A compact yet comfortable layout is about 2m x 2m with a 2.1m height, perfect for two to three people.
Electric vs. wood-burning sauna, which one should I choose?
Electric heaters are convenient and precise, while wood-burning heaters offer that classic experience but need a flue and must comply with smoke control rules. If you want a more effective heating system, go for infrared.
Can I build a DIY sauna myself or hire professionals?
If you’re confident with tools, a DIY build is achievable. But always hire an electrician for wiring and a HETAS-certified installer for wood-burning systems.
How long does a sauna last?
With good care, cleaning, annual wood treatment, and steady ventilation, a home sauna can last 20 years or more.