How to Build a DIY Hot Tub (Concrete or Wood Fired Spa)

Imagine having your own hot tub in your backyard without spending a lot. The answer just might be to build a DIY hot tub.

It’s a fun project that lets you relax outdoors. With just a garden hose and some creativity, you can make your backyard a peaceful spot.

Having a hot tub at home is a dream for many. With the right help, you can make it happen. This article will guide you through building a DIY hot tub. We’ll cover the basics, planning, and how to build both wooden and concrete tubs.

The best part?

Below, I give you detailed instructions on not only a wooden DIY hot tub, and a concrete one. But I also show you how to do it with inexpensive cinderblocks and just using a simple steel stock tank.

An outdoor construction site in someone's back yard. the ground has been dug up about 8 inches down in a square shape

Understanding DIY Hot Tub Basics

Building a DIY hot tub can be exciting. Wooden hot tubs are a favorite for their natural look. They can be heated with a wood-fired system, making for a cozy soak. But, they need regular care to keep the wood in top shape.

Concrete hot tubs are another option. They’re durable and need less upkeep but can cost more. An electric heater is a budget-friendly choice. Paired with a filtration system, it ensures a clean soak.

When building a DIY hot tub, consider a few things:

  • Cost: The price of materials and equipment, like the electric heater and filtration system.
  • Time: The effort needed to build and keep the hot tub clean, including wooden tubs.
  • Skill: The level of skill needed to build and install the hot tub, including the wood-fired heating system.

Knowing these points helps make the right choices for your DIY hot tub. This way, you can enjoy a relaxing outdoor soak.

a wooden jacuzzi or hot tub filled with water, emanating steam

Building a Wooden Hot Tub From Scratch

A DIY wood-fired hot tub brings the magic of natural hot springs to your backyard. This project takes time and patience, but the final product is worth every effort. Let’s break down the process into manageable steps.

Choose Your Location

Pick a flat spot with easy access to both cold water and drainage. The edge of the yard works well, but make sure the ground can support the volume of water you’ll add. Consider building a concrete pad as your foundation – you’ll need it to hold roughly 700 gallons of water.

Gather Materials

Start with high quality cedar planks – they’re naturally resistant to water damage. You’ll need stainless steel bands for support, a water heater (wood-fired or electric), plumbing fixtures, and waterproof sealant. The project cost varies, but expect to spend between $2,000-3,500 for materials.

Build the Base Ring

Create your tub’s foundation by arranging cedar planks in a circle. The final length of each plank affects your tub’s size. Most DIY hot tubs are 6-7 feet across, similar to commercially available tubs.

Stack the Walls

Layer cedar planks horizontally, offsetting the joints for strength. The outward force of warm water is powerful, so use temporary straps as you build up the walls. Each layer must be perfectly level and snug against the one below it.

Install Support Bands

Place stainless steel bands every 12 inches up the outside wall. These crucial supports hold everything together when filled. Think of them like a belt around the tub – they need to be tight but not warping the wood.

Plumbing Installation for Wooden Hot Tubs – Step by Step

Plumbing a wooden hot tub requires special attention to wood movement and water-tight seals. Since wood expands and contracts, flexible connections are crucial for long-term success.

Required Components

You’ll need a bottom drain assembly, through-wall fittings for circulation, flexible PVC pipe and connections, a skimmer box, and high-quality silicone sealant. Choose marine-grade brass or stainless steel fittings to prevent corrosion.

Pre-Assembly Planning

Plan your plumbing layout before assembling staves. The main drain goes in the center of the floor. Install the intake fitting about 8 inches up from the bottom and return lines 18 inches below water level. Position the skimmer between staves for easy integration.

Installation Process

Install floor drain before assembling tub walls. Use flexible gaskets between wood and fittings to allow for movement. Mount through-wall fittings after the staves are assembled but before adding support bands.

Create a pump pad nearby, keeping equipment within 15 feet of tub. Use unions and flexible connections where pipes exit the tub to prevent stress cracks. Consider a sliding joint system that accommodates wood expansion.

Testing and Special Considerations

Test all connections with cold water first. The wood will swell, tightening around fittings. Check seals again after 24 hours of soaking. Add thread sealant to all mechanical connections.

Install valves for easy winter drainage in cold climates. Run pipes underground or insulate well if exposed. Remember that wooden tubs need periodic tightening of bands, which can affect plumbing alignment.

Seal Everything

Apply several coats of marine-grade sealant to all wood surfaces. Pay extra attention to joints and around fittings. Take your time here – rushing this step leads to leaks.

Test and Adjust

Fill the tub with cold water first to check for leaks. The wood will swell a little bit, helping create a better seal. Let it sit for 24 hours, then drain and fix any problems before adding your heating system.

Final Touches

Add steps, benches, or a cover to complete your spa. Many DIY builders create a surrounding deck for comfort and safety. Regular maintenance with wood preservatives helps your tub last a long time.

Remember, this project requires patience and attention to detail. A well-built wooden hot tub can last decades, providing years of relaxation in your own backyard oasis.

A man is seated inside a large concrete rectangular hot tub frame, which seems to be unfinished or under-construction

Building a Concrete Hot Tub

Creating your own DIY hot tub from concrete is like building a small swimming pool. While the project cost runs higher than inflatable hot tubs, this permanent outdoor hot tub will last for decades. Let’s dive into the construction process.

Plan Your Design

Sketch detailed hot tub plans before starting. Most home builds are 6-8 feet wide and 3-4 feet deep, holding about 500 gallons of water. Consider adding built-in seating and steps for easy access. The edge of the yard often works well, but ensure you’re away from utility lines.

Prepare the Site

Excavate the area about 6 inches deeper than your planned tub depth. Create a level base with crushed gravel, then add a 4-inch concrete foundation pad. This base needs to cure for at least a week before continuing.

Build the Framework

Construct sturdy wooden forms for your walls using 2x4s and plywood. The final length should match your design exactly. Add steel rebar in a grid pattern, keeping it 2 inches from the form walls.

Pour the Concrete

Place all plumbing fixtures before pouring concrete. (see below).

Mix and pour high quality concrete in stages. The floor goes first, then the walls. Use a concrete vibrator to remove air bubbles that could cause leaks. Keep the concrete damp while curing to prevent cracking.

Plumbing Installation for Concrete Hot Tubs – Step by Step

Plumbing a concrete hot tub requires careful planning as mistakes can’t be fixed once the concrete is poured. This system needs to last decades, so using high-quality materials is essential.

Required Components

You’ll need a main drain with anti-entrapment cover, multiple jet fittings, a skimmer system, air intake fittings, PVC pipes and fittings, and a hydrostatic relief valve. Schedule 40 PVC is minimum standard – Schedule 80 offers better durability for hot water use.

Pre-Pour Planning

Create a detailed plumbing diagram showing all pipe runs. Install the main drain at the lowest point with a secondary drain for safety. Position jets 18 inches below water line, typically spaced 12-18 inches apart. Place skimmer on the downwind side, with the water level halfway up the opening.

Installation Process

Secure all fittings to your rebar grid before pouring concrete. Run PVC lines in curved patterns rather than straight runs to allow for thermal expansion. Group pipes in channels where possible to minimize concrete penetration points.

Create separate manifolds for jet zones, allowing individual control. Include access panels in your design for future maintenance. All pipes must slope toward drains, typically 1/4 inch per foot.

Testing and Verification

Pressure test entire system at 35 PSI for 24 hours before pouring concrete. Have plumbing inspected if required by local code. Fill all lines with water during the concrete pour to prevent crushing.

Install valves at key points for maintenance and flow control. Consider adding a blower line for air jets – it’s much harder to add later. Document all plumbing locations with photos and measurements before covering with concrete.

Waterproof the Shell

After the concrete cures for about two weeks, apply several layers of waterproof coating. Pay special attention to corners and around fittings. This protective barrier keeps warm water from seeping through the concrete.

Add Finishing Touches

Install tiles, coping stones, or other decorative elements. Many builders add mosaic tiles or smooth river rocks for a natural hot springs look. Consider building steps or benches around the outside for convenient entry.

Install Equipment

Set up your pump, filter, and heater system. Most DIY builders choose an electric spa pack over wood-fired options for consistent heat. Test all connections with cold water before final setup.

Final Testing

Fill the tub and run all systems for several days. Check for leaks, proper circulation, and heating. Adjust chemical levels and ensure all safety features work properly.

Remember that concrete hot tubs require serious planning and effort, but the final product is worth it. Take your time with each step – rushing leads to problems that are difficult to fix later. With proper maintenance, your custom spa will provide relaxation for many years to come.

An outdoor construction site for an inground hot tub. The main structure is made from cinder blocks glued together with a few holes, for plumbing

Building a Cinder Block Hot Tub

Creating a hot tub from cinder blocks offers a middle ground between wooden and concrete designs. This DIY project costs less than commercially available tubs while providing the durability of stone. The final product holds about 500 gallons of water and can last a long time with proper maintenance.

Plan Your Layout

Draw detailed hot tub plans before starting. A typical size is 6×6 feet square, using standard cinder blocks. Choose a location with easy access to water and electricity. The edge of the yard works well, but ensure the ground can support the weight.

Prepare the Foundation

Dig down 8 inches and create a level base with gravel. Pour a 4-inch concrete pad slightly larger than your planned tub size. This foundation needs to cure completely before building walls.

Lay the First Course

Start with a level row of cinder blocks around the perimeter. Use masonry adhesive between blocks for extra strength. Check each block with a level – this first row determines how straight your walls will be.

Build the Walls

Stack blocks in a staggered pattern, filling cores with concrete as you go. Add rebar through the cores every few blocks for support against outward force from warm water. Most tubs need 4-5 rows for comfortable depth.

Plumbing Installation for Cinder Block Hot Tubs – Step by Step

Installing plumbing in a cinder block hot tub requires planning ahead since you can’t easily modify it later. Taking time during this stage prevents costly repairs down the road.

Required Components

You’ll need a 2-inch main drain assembly, multiple 1.5-inch return fittings for jets, a skimmer box, PVC pipes and fittings, and waterproof sealant. Consider adding an overflow drain near the top edge. All fittings should be rated for hot water use.

Pre-Installation Planning

Mark all plumbing locations before laying your final block courses. The main drain goes in the deepest part, usually center bottom. Place jet returns about 18 inches below water level, spaced evenly around the tub. Install the skimmer on the downwind side to catch debris effectively.

Installation Process

Set plumbing fixtures as you build the walls, securing them with hydraulic cement. Run PVC pipes through block cores where possible to protect them. Create a manifold system behind the tub to control individual jets. All pipes should slope slightly toward drain points to prevent air locks.

Install an equipment pad nearby to house your pump, filter, and heater. Keep it within 10 feet of the tub to maintain good water pressure. 

Testing and Final Steps

Pressure test all lines before covering them with concrete. Run each system separately to check for leaks or air locks. Install unions at key points for easier future maintenance.

Consider adding air lines for therapy jets – they dramatically improve the spa experience. Always insulate pipes in cold climates to prevent freezing and improve efficiency.

Waterproof Interior

Cover interior walls with concrete board, then apply several layers of waterproof membrane. Pay special attention to corners and plumbing penetrations. This barrier prevents leaks and protects the blocks.

Add Interior Finish

Install a high quality pool liner or apply waterproof concrete coating. Many builders add tiles for comfort and style. Create benches using concrete blocks or frame them with treated lumber.

Equipment Setup

Install your pump, filter, and heating system. Test all connections with cold water first. Consider building an equipment housing to protect components from weather.

Final Steps

Build steps or a small deck for easy entry. Add exterior finishing like stone veneer or paint to match your landscape. Consider a cover to keep heat in and debris out.

Remember that while cinder block construction seems simple, attention to detail matters. Take time waterproofing and checking for level surfaces. The effort you put into construction directly affects how long your outdoor hot tub will last.

a large round metal tank filled with water. Adjacent to the tank, on the right, is a white tank with the label 'Electrolux'

Building a DIY Stock Tank Hot Tub

Converting a stock tank into an outdoor hot tub is one of the easiest DIY project options. While not as luxurious as commercially available tubs, these simple spas cost far less and can be built in a weekend. Most tanks hold 100-300 gallons of water, perfect for 2-4 people.

Choose Your Tank

Select a high quality galvanized steel or polymer stock tank. Round tanks typically run 6-8 feet in diameter and 2 feet deep. Larger oval tanks work well if you want more of a small swimming pool feel.

Prepare the Site

Create a level base using crushed gravel or concrete pavers. The edge of the yard works well, but ensure easy access to both water and power. Add landscape fabric under your base to prevent weeds from growing.

Plumbing Installation for Stock Tank Hot Tubs – Step by Step

Installing plumbing in your stock tank hot tub requires careful planning and the right tools. Most setups need just a few key components to create proper water circulation and heating.

Required Components

You’ll need a 1.5-inch bulkhead fitting for the drain, two 1-inch bulkhead fittings for circulation, PVC pipe and fittings, thread sealant, and a hole saw kit. Choose high-quality marine-grade fittings to prevent corrosion and leaks.

Installation Steps

Start by marking your hole locations. The drain goes at the lowest point, usually near the bottom edge. Place intake (suction) about 18 inches up on one side and the return line on the opposite side at the same height.

Cut holes using appropriate-sized hole saws. Clean the edges and apply silicone sealant around each hole before installing bulkhead fittings. Tighten carefully – overtightening can crack the fittings.

Connect your pump’s suction line to the intake fitting using PVC pipe. The return line connects to your heater output, then back to the tank. Use sweep elbows instead of sharp 90-degree turns to improve water flow.

Testing

Fill the tank partially and check all connections for leaks. Run the pump for several hours before adding chemicals or heat. Listen for any unusual sounds that might indicate air in the lines.

Consider adding a skimmer basket to your intake line to catch debris. Ball valves on both lines help with maintenance and troubleshooting. Always use primer and PVC cement on pipe connections for watertight seals.

Add Heating System

Choose between electric or DIY wood-fired heating. Electric spa packs offer convenience but cost more. Wood-fired options use copper coils to heat the water naturally, similar to old bathtub setups in natural hot springs.

But bear in mind if you want ongoing year-round use, an electric spa pack like this one on Amazon will always be on (until you turn it off) and is low maintenance.

Set Up Filtration

Install a small pump and filter system to keep water clean. Above-ground pool equipment works perfectly for this project cost range. But make sure to get something that is the same pipe and thread size and type as your heater.

Mount everything on a nearby platform for easy maintenance.

Add Seating

Create comfortable seating using cedar boards or plastic bench kits. Secure everything well – floating benches can be dangerous. Consider adding non-slip mats on the tank bottom for safety.

Insulate the Tub

Wrap the outside with foam insulation boards to help retain heat. Cover the insulation with weather-resistant material like corrugated metal or wooden slats. This step dramatically reduces heating costs.

Install Controls

Set up temperature controls and timers for your heating and filtration systems. Keep electrical components protected from weather and splashing. Consider adding LED lights for nighttime use.

Final Touches

Build steps or a surrounding deck for easy entry. Add a cover to maintain temperature and keep debris out. Consider installing jets if you want more than just a soaking tub.

Remember that while stock tank hot tubs are simpler than other options, proper setup ensures your final product lasts a long time. Regular maintenance and water care are essential, just like with any spa. With good care, these DIY tubs can provide years of relaxation at a fraction of the cost.

How much does a DIY Hot Tub Cost to Build?

Building your own hot tub can save thousands compared to a commercially available tub. The final cost depends on your specific needs, chosen heat source, and whether you’re using new or upcycled materials.

Type Low End Average High End
Stock Tank Hot Tub $800 $1,500 $3,000
Wooden Hot Tub $2,000 $3,500 $5,000
Cinder Block Hot Tub $1,500 $2,800 $4,500
Concrete Hot Tub $3,000 $5,000 $7,500

The biggest challenge is often choosing between different heating options. Electric heaters and heat pumps cost more upfront but offer convenience. Wood-fired heaters using copper tubing cost less initially but require more effort for each relaxing soak. Adding features like spa jets or a spa controller increases costs but improves the experience.

Remember that these prices assume doing all work yourself. Hiring help for complex tasks like plumbing or concrete work can add significantly to the total.

YouTube player

Conclusion

As you finish your DIY hot tub project, you should feel proud of creating a special place for relaxation. You might have built a wooden, concrete, or endless pool hot tub. The success of your hot tub comes from careful planning and doing things right.

Choosing the right spot and designing your plunge pool showed your creativity and problem-solving. Using a snorkel stove or kW heaters for heat shows your resourcefulness. You’ve made a hot tub that stands out.

Putting on the hot tub cover and setting up the water system is a big accomplishment. Your DIY solar hot tub is a sign of your creativity and a great option for a personal oasis.

As you complete your hot tub, remember the journey is the best part. You’ve faced challenges, learned new skills, and will enjoy your new haven.

Frequently Asked Questions

Is it cheaper to build or buy a hot tub?

Building your own hot tub typically costs 50-70% less than buying a commercially available tub with similar features. A new store-bought spa runs $5,000-15,000, while most DIY projects using upcycled materials cost $1,500-5,000.

However, the trade-off comes in time and effort. Your specific needs determine whether the savings are worth it. Consider that a DIY tub needs more maintenance and might lack features like high-speed spa jets that come standard in store-bought models.

What is a redneck hot tub?

A “redneck hot tub” typically refers to a stock tank pool or metal tanks converted into a basic soaking tub. These DIY setups often use upcycled materials and simple heat sources like wood-burning stoves or copper coil systems.

While some view the term as derogatory, these innovative builds often show creative problem-solving. Many feature clever heating systems using copper tubing wrapped around heat sources for a relaxing soak at a fraction of traditional spa costs.

What is the cheapest base for a hot tub?

The most affordable base for a hot tub is a leveled gravel pad topped with pavers from your local home depot. This setup costs around $100-200 and works well for lighter tubs like stock tank pools or wood frame designs.

For heavier builds, pour a 4-inch concrete slab reinforced with rebar. While more expensive at $300-500, it provides the stable foundation needed for concrete or metal tanks filled with water.

How do you put jets in a DIY hot tub?

Installing spa jets requires careful planning and specific parts designed for your water depth. Start by choosing jet locations – typically 18 inches below water level and spaced evenly around the tub.

Each jet needs three components: a jet body that mounts through your tub wall, water lines for pressure, and an air line for bubbles. The biggest challenge is matching your pump’s flow rate to the number of jets you install.

A typical DIY setup uses 4-6 jets powered by a 1.5 HP pump. Install a spa controller to adjust jet pressure and manage water temperature. You’ll need to cut precise holes in your tub wall – use a hole saw or router table for clean edges.

Most builders get parts from hot tub supply stores rather than the local Home Depot, as these specialized components handle high-speed water flow better. Plan to spend $300-600 on a basic jet system.

Do you need a cover on a DIY hot tub?

Do you need a cover on a DIY hot tub?

Yes, a cover is essential for any DIY hot tub to minimize heat loss and keep debris out. Without proper covering, your heat source – whether it’s a heat pump or wood-fired heater – will work much harder to maintain water temperature.

A well-insulated cover can cut heating costs by up to 70% and protect your water supply from leaves and dirt. Even on sunny days, an uncovered tub loses significant heat through evaporation. Heat loss happens fastest at the water’s surface, making a cover your most important efficiency upgrade.

The best covers have a solid core of 2-inch foam insulation wrapped in marine-grade vinyl. You can build a simple wood frame cover with rigid foam insulation for about $200, or invest in a commercially available tub cover cut to your specific needs for $300-500. While it seems expensive, the investment pays for itself in energy savings within months.

Consider adding a cover lifter system too – they make it much easier to remove and replace heavy covers. Without a lifter, covers often get dragged on the ground, leading to damage.

Rather buy a new hot tub than build one?

I get it! But before you rush off to the dealer, make sure you check out my 23 Crucial Things to Know Before Buying Your First Hot Tub article.

It’s still worth a read if you’re DIYing it too! Just click that link to read it on my site.

Jeff Campbell