Alternatives to Gunite and Shotcrete: 3 DIY-Friendly Methods

Last updated: September 2026

If you’ve been searching YouTube for how to build a hot tub or pool, you’ll have come across gunite and shotcrete. They’re really, really cool to watch. Concrete gets sprayed at high pressure onto a rebar cage, then trimmed and troweled into a perfect, joint-free shell, all in a day. The only real downside is that they’re not for DIYers like you and me.

The good news is that building your own hot tub isn’t just for the professionals. In this post I’ll explain what gunite and shotcrete actually are, then look at the DIY alternatives that don’t need any specialist equipment.

Gunite and shotcrete explained

If you haven’t seen it, search for a gunite pool video and watch these amazingly skilled people spray the concrete. They trim and trowel it flat, and you end up with a shell with no joints at all. It’s done in a day and then left to cure.

A little bit of history

The process was invented by Carl Akeley, an American taxidermist, who developed a “cement gun” in 1907 to repair the Field Columbian Museum in Chicago. He was granted patents for the cement gun and for “gunite” in 1911. According to Wikipedia’s history of shotcrete, the name Gunite was trademarked in 1909 and it later became the registered trademark of Allentown Equipment, the oldest maker of gunite equipment.

Because “Gunite” was a trade name, the industry needed a generic term. “Shotcrete” came into use in the 1930s, and in 1951 the American Concrete Institute adopted it as the official generic name for sprayed concrete, to avoid proprietary names.

What’s the actual difference?

The difference isn’t really a material. It’s the process:

	Gunite (dry-mix shotcrete)	Wet-mix shotcrete
How it works	Dry cement and sand are blown down the hose and the water is added at the nozzle.	Ready-mixed concrete is pumped down the hose and air is added at the nozzle.
Who controls the mix	The nozzle operator, who controls the water as it sprays.	The batching plant.
Rebound and dust	More	Less. Wikipedia notes the wet process generally produces less rebound, waste and dust.

So “gunite vs shotcrete” is really “dry-mix vs wet-mix”. Either way, both need a rig, an experienced nozzle operator and a crew. That’s not a DIY job.

What about hiring a crew just for the shell?

That’s an option. Some people hire a shotcrete crew to shoot the shell and then do everything else themselves. For a small hot tub, though, the minimum charge and the kit needed often make it hard to justify, and you still need the rebar cage and plumbing ready and inspected before they arrive. Get quotes if you’re curious. For most of the people I help, one of the three methods below makes more sense.

DIY alternative 1: a block-built hot tub

The first alternative is block. You can call them cinder blocks or CMU blocks (concrete blocks in the UK). The process is much the same, and it’s how I built my own hot tub. I founded buildahottub.com to share what I learned from that build, and block is still one of the easiest methods, especially for a square or rectangular tub.

Start with a proper base

About 4in of crushed rock with a 4–6in slab in a timber form is a reasonable pad for a shop-bought tub sitting on top of it, but a built tub is a vessel holding a few tonnes of water. For that I’d lay 100–150mm (4–6in) of compacted Type 1, sand blinding and a DPM, insulation if it’s in-ground, and then a reinforced ready-mix C25/C30 slab about 150mm (6in) thick. The main drain and a hydrostatic relief valve go in before the pour. My DIY in-ground hot tub build guide covers it step by step.

The walls

On top of the slab, build your walls using hollow blocks (8in CMU in the USA, or 215mm hollow blocks in the UK). Drop #3 rebar into the cores. That’s 3/8in, or about 10mm, although your plans or engineer set the size and spacing. Tie it to starter bars from the slab and fill the cores with concrete. It works whether you’re building above or below ground. The full walkthrough is in Cinder block hot tub: a DIYer’s guide.

Block is great for straight lines. If you want a round tub, a kidney shape or curves, then unless you’re a particularly skilled block layer (I’m not, I can only put them in a straight line!) you’ll want one of the next two methods.

DIY alternative 2: a poured concrete hot tub

You still need the same reinforced slab. But for the walls, you build a timber mould (called a form) on each side and fill it with concrete. Inside the form goes a rebar cage and your plumbing.

Rebar spacing: Typical residential pool practice is #3 bar on a 12in grid, tighter at stress points, with about 3in of concrete cover to the earth. That matches what I say in my rebar guide. Your engineer or plans have the final say.

Once the rebar is in, tie the plumbing to it and pressure test it. Then close up the outer form, brace it well (wet concrete pushes hard), and pour. Order ready-mix and pour in one go to avoid cold joints, and use a poker vibrator to get rid of voids around the pipes. Once it’s cured, strip the forms and you have your walls. If the plumbing is inside the walls, allow at least 10in (250mm) of wall thickness for the gunite jet bodies.

DIY alternative 3: ICF (the one I’d pick)

This is my first recommendation. ICF (insulated concrete forms) are hollow polystyrene blocks that dry-stack like Lego for adults. You put rebar inside, fill them with concrete, and get a reinforced concrete wall with insulation on both faces in one go. They’re light, easy to cut for plumbing, and far less work than building timber formwork. See What are the best ICF blocks for building a hot tub? and Adam’s ICF hot tub build.

The alternatives compared

Method	Shapes	Special kit	Insulation	DIY difficulty
Gunite / shotcrete	Any	Rig and crew	Add separately	Not DIY
Block (CMU)	Square and rectangular	Mixer, core drill	Add separately	Moderate
ICF	Mostly straight, and curves with planning	Bracing, ready-mix	Built in	Easiest
Poured in forms	Any, including curves	Formwork, bracing, vibrator	Can be cast in	Hardest

Whichever you pick, the finish is the same: render or smooth the walls, apply a pool-rated membrane in two coats (Ardex S 7 Plus in the UK or Laticrete Hydro Ban in the USA), flood test, then tile. There’s more in Waterproofing, grout and tile adhesive, and a broader overview in DIY hot tub construction methods.

I know I’ve gone over these methods quickly. On my YouTube channel there are videos that go through the processes in much more detail.

Planning your own build?

If you need plans, my DIY hot tub plans give you CAD drawings, the plumbing layout, a shopping list and a video course. If you’re after something out of the ordinary, design it in the free Tub & Pool Designer Pro software and I can turn it into architectural CAD and a 3D plumbing design. For parts, head to parts4tubs.co.uk (UK) or parts4tubs.com (USA).

FAQs

What is the difference between gunite and shotcrete?

Both are sprayed concrete. Gunite is the dry-mix process, where water is added at the nozzle. Wet-mix shotcrete pumps ready-mixed concrete. Shotcrete is the umbrella term for both.

Can I apply gunite myself?

Not realistically. It needs a gun or pump, a compressor, and years of nozzle skill. DIYers are far better off with block, ICF or poured walls.

What is the cheapest alternative to gunite?

Usually concrete block, as the materials are cheap and widely available. ICF costs more per block but saves time and gives you insulation, which saves on running costs.

Is a block or poured hot tub as strong as gunite?

Built properly, yes, for a hot tub. That means rebar in the slab and walls tied together, filled cores or a well-vibrated pour, and a proper waterproofing membrane.

Can I build a curved hot tub without gunite?

Yes. Poured concrete in timber or flexible forms handles curves, and some ICF systems can do curves too, with planning.

Which method are you going with? Let me know 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