DIY Hot Tub Construction was something I was struggling finding information about. buildahottub.com was established as I could not find the information I needed as a DIY Hot Tub builder myself. I searched the internet and was looking for information on how to perfect my skills and build that perfect tub. I researched everything from building spas, to hot tubs, to swim spas, to plunge pools, but I just could not find the information that I needed.
This then became my mission. My raison d’être and this was to become the most helpful resource on the internet for the DIY Hot Tub builder looking for DIY Hot Tub Construction methods and technical know how.
DIY Hot Tub Construction to me seemed something different from a commercial built pool. The prices that those guys charge were just astronomical so what I was looking for was a much more cost effective way of doing things. I found just that.
In this blog post I want to really focus on just the hot tub construction methods that are accessible to the average DIYer. It must be said of course that the DIYer that is looking to undertake such a project, it going to need some basic skills. That said, I have proved myself and time and time again for my customers (just look a the case studies available on this website) that it is totally possible to construct your own DIY Hot Tub.
Below is a picture of my own tub. Absolutely love it!
Let’s start this article by looking at what methods of DIY Hot Tub constructions are not accessible to us all.
Gunite & Shotcrete are not DIY Hot Tub Construction Methods – these are for the Pros!
Gunite and Shotcrete are NOT DIY Hot Tub Construction methods. These are methods that are best left to the pros! Both of these methods involve concrete being sprayed into a rebar structure at high pressure. This concrete is then smoothed out and polished in situ.
This method is not for the DIYer and takes a lot of skill and practise. Think about plastering. When you DIY plaster, it might be ok, but it is not as good as when a Pro comes and does it. This is exactly the same for the Gunite and Shotcrete. Leaving the machinery that one would need aside, this method is just not going to be any good as a method of construction for a DIY Hot Tub.
Don’t be scared!
The thing with building a DIY Hot Tub is that it can be a little daunting. The prices that you can be quoted can be a little scary. I know that two of my Case Studies, Ray and Kyle were quoted huge sums of money to construct their dream DIY Hot Tubs.
Ray, his builders wanted around $45 000, he ended up building his for around $12 000. Kyle, given the rural location of his home, he was being quoted in excess of $100 000. Yes, you read that correctly, $100 000 to build a DIY Hot tub. Ouch.
The good think here to bear in mind is that the DIY Hot Tub construction methods that I will summarise below will save you a ton of money. Most of my customers build their entire project for under $10 000 and comfortably under this number.
So what are they I hear you ask?
What are the DIY Hot Tub Construction Methods available to us?
When it comes to DIY Construction methods, I think there are two that we can consider. Both of these methods my customers have successfully used to construct their own DIY Hot Tubs.
Construction Method #1 – Block Build DIY Hot Tub
Construction Method #2 – Poured Concrete DIY Hot Tub
Firstly, let’s concentrate on the parts of this DIY building process that are going to be common across the two methods.
Step 1, the planning.
The planning has to be one of the important parts. Without a good plan, you are going to fail. Failure could come in a number of ways. Either, your hot tub is not going to work.. Or, it is going to end up costing you a small fortune to get someone in to “fix” what you have built.
Neither of these options are good ones so there are some options that you have here of how I can help you.
In my online shop, you will find ready-made designs that you can purchase and use. They come with all the information you need to complete the project.
I have an online course that will teach you exactly what you need to know about designing and building your own DIY Hot Tub. This is ideal as it is the exact process that I use to design hot tubs for customer.
And finally, I can of course design the hot tub for you and guide you through the build process.
All three of these methods are going to help you with the planning stage of your build.
Step 2 – Clearing and preparing the area
It’s pretty obvious I guess that you are going to need to clear the area of any debris. Get rid of the trees, shrubs and the like. The last thing you want is some roots coming up into your DIY Hot Tub!
You are probably going to want to hire a small excavator or digger to help you do this. Especially if you plan to have your DIY Hot Tub in ground or even partially in ground.
You may have already read on this blog that I could not get either of these into my garden when I built my own hot tub so I had to do it by hand. This was back breaking work. Of course it was well worth it in the long run, but back breaking none the less.
Once you have cleared the area and you are down at the desired level, it is time to move to the next stage of your build.
Step 3 – Laying a concrete base or pad
Both of the two methods that I have highlighted above do require that you build a DIY concrete pad or base for your hot tub. Now, I am not going to go into detail in this particular blog post on the ins and outs of how to build one as I have a really detailed blog post here.
That said, here is a short summary. First, you are going to need to put down 10cm or 4″ of crushed rock or type 1 as it is often know. Next, you will need to compact this with a machine.
Then it is time to build a wooden frame that is going to house your concrete pad or base. The frame will be 100% level so you can skim easily over the top when it is full of concrete.
Next, you are going to add a rebar mesh that will be supported with either stands or just rocks so that it is not sat on the bottom. The idea is that your rebar is going to be in the middle of your pad for strength.
Mix and pout the concrete. Let it set then remove the wooden form. Voila – concrete hot tub pad done!
Construction Method #1 – Block Build DIY Hot Tub
In my opinion, having now completed lots of projects with customers, as well as my own tub, I think that block built tubs are the easiest construction method to use for hot tubs. Firstly, you are going to need to lay an outer wall around the perimeter of your tub. This is exactly the same whether you are building above or below ground.
The other wall should be made up of usually 4″ wide blocks and they can be strengthened by adding rebar into the centre. These hollow blocks are then filled with concrete to give the walls their strength.
A Block Build DIY hot tub refers to the construction of a hot tub using concrete blocks or cinder blocks as the primary material. This approach involves assembling and arranging these blocks to create the structure of the hot tub, which is then finished with various materials such as tiles, plaster, or waterproof coatings.
The benefits of using blocks for a DIY hot tub construction include:
Affordability: Concrete blocks are relatively inexpensive compared to other building materials such as wood or pre-formed hot tub shells. This makes them a cost-effective option for constructing a hot tub on a budget.
Durability: Concrete blocks are known for their strength and longevity. They can withstand harsh weather conditions, are resistant to rotting or warping, and can handle the weight and pressure of the hot tub water.
Customization: Building a hot tub with blocks offers flexibility in terms of design and size. You can create a custom shape and size to fit your specific needs or available space. The blocks can be easily modified or cut to accommodate plumbing and seating arrangements.
Heat retention: Concrete blocks have good thermal mass, meaning they can absorb and retain heat. This can help in maintaining the water temperature in the hot tub, reducing the energy required to keep it warm. Even more so when you add the insulation to them as I explain further down this article.
Structural stability: Blocks provide a solid and stable foundation for the hot tub. When properly constructed and reinforced, they can support the weight of the water and occupants without sagging or shifting.
Ease of construction: Block construction can be a suitable option for individuals with basic DIY skills. The materials are readily available, and the assembly process is relatively straightforward, especially when compared to more complex construction methods.
It’s worth noting that while block-built hot tubs offer advantages, the construction process requires careful planning, proper insulation, and waterproofing measures to ensure the longevity and functionality of the tub.
Once you have the outer walls in place, you can then concentrate on the interior. Any steps that you are going to have go in now as well as the seating. It should just be the retaining walls at this point as we still need to add the plumbing.
Once we have the outer walls for the tub, as well as the interior ones for the seating, it is time to add your plumbing. You will need to core holes in the blocks so that your Gunite bodies can be inserted into the block work. This is shown in the image below. Here was can see the lower jets which penetrate from the exterior wall and go all the way through the seats into the tub.
With the plumbing all in place, and some insulation too, you can then go ahead and fill in the interior seating and steps with a backfill of concrete. As you can see, this DIY Hot Tub construction method is pretty simple to follow.
Then it is time to do the same on the backs of the seats. Holes need to be cored so that you can add the Gunite Bodies to put jets in. Once you have all the jets in and the pipework connected up, you can think about insulating your tub. At this point, you can also do a water test if you wish as shown below.
Seal and Tile
Once you have checked if there are any leaks, the next steps are to actually seal up your interior. Once you have drained out the water of course! To seal the interior I would recommend that you skim the surface with a waterproof render. Then, once sealed, I would use tiles to finish the tub off. They look so much better than a pained surface in my opinion. Even if they do cost quite a bit more. It is definitely worth saving the money up for the tiles!
You can see on the image above that a second skin of brick has been erected to cover up the pipework. This is because this particular tub was built partially in ground and partially. That meant that visually, the pipework needed to be covered. If you are building an in ground tub, this step is generally not needed.
What you end up with is is pretty spectacular. Whilst the DIY Hot tub construction method is much simpler than a commercial one, it has all the look and feel of a tub that can cost up to 5 times as much!
Construction Method #2 – Poured Concrete DIY Hot Tub
DIY Hot tub construction by means of pouring concrete, is a little but more involved than building from blocks. The first thing that you should note, is that there is a lot more preparation in terms of the metal rebar structure.
The metal rebar is going to give your concrete the strength that you need and stop it cracking. In most cases, you will be using a #3 rebar which is 10mm or 0.4″ thick and you will be making what looks like a wire frame for your hot tub. The rebar not only will be in the base or pad as we have seen above, but it will be in all of your walls and even in the seats and steps too.
Creating the Form
Creating the form or mould for the walls is the next step. This involves erecting a wooden mould or form that you will fill with concrete to create your walls. The form will be on either side of your rebar and the rebar will be in the centre of the wall to give it the strength that it needs.
You are going to start with the inner wall first. This is because once you have the inner wall in place, you will then need to add the plumbing to your rebar. What is different about a poured concrete hot tub versus a block built one, is that most of the plumbing will actually be encased in concrete and be inside of the walls.
Adding the Plumbing
In a poured concrete DIY Hot tub construction, you are going to need to tie your plumbing onto your rebar. You are going to do this before you add the exterior form and before of course you pour the concrete. When you have added all the plumbing you should have something that looks a little like the image below.
With all the plumbing now in place and tied into your rebar, it is time to add the exterior form or wooden walls.
With the forms for the walls in place, the next step just before you pour the concrete is you are going to need to brace the walls. There is a huge amount of weight that is needed to be supported when you pour the concrete, so it is really important that you are bracing the walls with as much structural timber as possible. If you are not sure how much, add some more. It will not harm things.
The last thing you actually want to happen is when you pout the concrete, your walls flex and you end up with a wall that is not flat and vertical.
With the bracing in place it is time to pour. I would recommend that you get a delivery of concrete and you then pour it in one go. You will get a much more uniform wall than if you are mixing it by hand as each of the concrete lifts may be slightly different in texture and colour. Not a big deal as you will be covering this with tiles anyway, but if you are going to do a job, you might as well do it properly.
Removing the forms
This is where it starts to get exciting. You can see what you have actually made at this stage. After leaving your concrete to cure for the right amount of time, usually several days, you can then remove the form. When you remove the wooden forms, it is usual that there will be areas that need sanding or touching up. This is the next stage of the process before you move onto sealing and waterproofing.
When you ordered or mixed your concrete, you should have asked for one with a waterproofing agent in or added it to your own mix. What these agents do is they reduce the amount of air bubbles in the mix. It is the air in the mix that causes the concrete to be somewhat porous. Reduce the amount of air in the mix and you are increasing the water resistance of the concrete.
Some Customer Feedback on Concrete Forms
Let me share with you the feedback I’ve received from some of my customers who opted for using forms and pouring the walls of their DIY hot tubs. They have found this approach to be incredibly advantageous in many ways.
Firstly, the use of forms provided them with a consistent and professional-looking shape for the walls, elevating the overall aesthetics of their hot tubs. By avoiding the need for expensive pre-made molds, they were able to save money and allocate those funds to other aspects of the projects.
The ability to customize the thickness and insulation of the walls during the pouring process ensured optimal heat retention and energy efficiency, which resulted in cost savings over time.
One of the significant benefits they mentioned was the ease of incorporating plumbing and electrical lines seamlessly into the structure, facilitating maintenance and future repairs.
The durability of the poured walls gave them peace of mind, knowing that their hot tubs would stand strong for years to come. Moreover, taking on the DIY aspect of the project brought a sense of pride and accomplishment to these customers, as they were able to relax in their very own handcrafted oasis.
Overall, based on the positive experiences of my customers, using forms and pouring the walls of a DIY hot tub offers not only aesthetic improvements but also practical advantages that make the entire process enjoyable and rewarding.
Sealing, Waterproofing and Tiling
Sealing, waterproofing and tiling is exactly the same process as we have already described in this article so I am not going to repeat that.
And the finished product – voila!
In Conclusion, Which DIY Hot Tub Construction Method Should you use?
In this article, I have highlighted the two most accessible hot tub construction methods for us DIYers. So which one should you choose? This is a tough question. I have already said that I think block built is easier, but if you are going for more adventurous design and shape, it might be easier to pour this rather than use blocks.
Either way, both of these methods are perfect of us DIYers and I will leave it to your good selves to decide which method suits you best.
Happy Hot Tubbin’
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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.
Today, I've helped over 900 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