Most hot tub shell materials fall into a few groups: acrylic backed with fiberglass or ABS, rotomolded plastic, vinyl liners, and inflatable PVC, with wood and metal at the niche end. The shell is the molded tub you sit in, and its material decides how the surface looks and feels, how much the tub weighs, how you clean it, and roughly where it sits on price. Every jetted hot tub in our listings that names its shell material says acrylic.
For seats, power, site and budget, start with our hot tub buying guide.
What are hot tubs made of? Shell, structure and cabinet
A hard-sided hot tub has three main layers. The shell is the water-holding surface with the seats, footwell and jet openings. Behind it is reinforcement that gives the shell its strength. Around it is insulation, a frame and the cabinet you see from the outside. When people ask what hot tubs are made of, they usually mean the shell.
See our guide to hot tub insulation for full foam vs perimeter foam.
Hot tub shell materials compared
Acrylic with fiberglass or ABS backing
Hot Spring’s article on what hot tub shells are made of describes the process: a single acrylic sheet is heated, placed over a mold, and vacuum formed so no air is trapped. Once it cools, it is reinforced with resin and fiberglass. In a variant, an ABS layer is applied to the sheet before molding. Hot Spring calls acrylic durable, available in many colors, and good at holding heat when well insulated, while noting it is heavier and costs more than vinyl or plastic.
Our American Spas listings describe “Fiber Steel Construction, a patented 7-layer laminate system reinforced with steel and wood,” plus a thick acrylic layer and a “resin-to-fiberglass mixture.” Several Canadian Spa Company listings say their spas use Lucite acrylic. The “ABS bottom insulated tray” in American Spas listings is a base pan, not the shell.
Rotomolded hot tub shells
Per Hot Spring, rotomolded tubs start as plastic powder that is heated in a mold and rotated until it coats the mold evenly. The result has a matte finish rather than a gloss, and it is relatively lightweight. Hot Spring’s view is that rotomolded tubs hold heat less efficiently, so owners typically pay more for electricity. We searched our catalog and found no listing that describes a rotomolded shell.
Vinyl liners and inflatable PVC
Hot Spring describes vinyl liner tubs as a liner over a frame, common with inground pools: inexpensive, but poor at holding heat, more likely to crack or tear, and prone to sun fading. It lists inflatable PVC as a less common option.
For a look at inflatable construction, our Tru Grit Fitness Inflatable Ice Bath ($999) is a cold tub, not a hot tub, but its listing describes a drop-stitched chassis “overlayed with a high grade PVC shell,” a 38 lb complete kit, and an included repair kit.
Wood and metal
Hot Spring notes wood was the main shell material until the 1970s and is now rare. Our Dundalk LeisureCraft Starlight Wood Burning Hot Tub CT372W ($5,471) is an example: the listing says it is lined with 5052 aluminum, has a white cedar skirt, western red cedar backrests and floor, and holds 233 gallons.
Acrylic vs rotomolded hot tub: side by side
| Material | Surface look | Weight | Price position | Heat and durability notes |
|---|---|---|---|---|
| Acrylic, fiberglass or ABS backed | Glossy, many colors | Heavier; best as a permanent install | Higher than vinyl or plastic | Holds heat well when well insulated; withstands normal wear for years |
| Rotomolded plastic | Matte | Relatively light, easier to move | Lower purchase price | Less efficient at holding heat, so higher running cost |
| Vinyl liner over a frame | Liner; can fade in sun | Depends on the frame | Inexpensive | Poor heat retention; more likely to crack or tear |
| Inflatable PVC | Soft sided | Not covered by our source | Not covered by our source | Less common per Hot Spring |
Rows summarize the Hot Spring article above. For lifespan estimates by construction type and brand warranty terms, see how long hot tubs last.
How the shell shapes seats, weight and delivery
Because an acrylic shell is formed over a mold, the seats, lounger and steps are part of that one formed piece. The Canadian Spa Montreal has “two comfortably molded seats and a full-length lounger,” and the Saskatoon pairs floor seating with bench seating.
Weight matters for delivery and the base. Listed dry weights for the acrylic tubs below run from 350 lb to 800 lb, and the Ottawa goes from 650 lb dry to 2,630 lb filled. One American Spas warranty section asks for a level surface, “ideally a 3 to 6 inch thick concrete slab depending on the spa’s weight.” Confirm your base with a contractor and your local building department.
Hot tub shell materials in our listings
Out of the hot tub listings we reviewed, every American Spas tub names an acrylic shell, a handful of Canadian Spa Company listings name Lucite acrylic, and our Cal Spas listings give a shell color but not the material. Where a listing does not say, the table reads “Not listed.”
| Hot tub | Shell material listed | Seats | Dimensions (in) | Dry weight | Price |
|---|---|---|---|---|---|
| Canadian Spa Saskatoon | Acrylic | 4 | 63 x 63 x 29 | 350 lb | $5,000 |
| Cal Spas Balboa PZ-516L | Not listed (High Gloss White) | 3 | 54 x 78 x 34 | 485 lb | $6,700 |
| American Spas 6-Person 45-Jet Lounger | Acrylic, fiberglass laminate | 6 | 84 x 84 x 36 | 800 lb | $7,700 |
| Canadian Spa Montreal Plug and Play | Not listed | 3 | 84 x 60 x 31 | 500 lb | $8,149 |
| Canadian Spa Ottawa | Lucite acrylic | 5 | 79 x 79 x 36 | 650 lb | $9,999.99 |
| American Spas 7-Person 72-Jet Bench | Acrylic, fiberglass laminate | 7 | 84 x 84 x 36 | 800 lb | $10,200 |
| Canadian Spa Burnaby | Lucite acrylic | 6 | 84 x 84 x 35 | 800 lb | $13,249 |
Prices are from our listings at the time of writing. See more models on our Canadian Spa Company brand page.
Cleaning and caring for an acrylic shell
Jacuzzi’s hot tub maintenance tips say acrylic shells are non-porous, so dirt does not penetrate, and a periodic wipe with a damp cloth keeps them looking clean. The Arctic Spas owner’s manual is stricter on products:
- Use a soft cloth or sponge for routine dirt.
- Baking soda or vinegar can be used for minor surface cleaning; rinse with fresh water.
- Do not use alcohol or household cleaners beyond those it lists.
- Do not use products with abrasives or solvents, which may damage the surface.
- Damage from harsh chemicals is not covered under its warranty.
Your own tub’s manual comes first.
Scratches, cracks and blisters
Warranties separate cosmetic marks from structural defects. One American Spas warranty section in our listings covers defects in the “fiberglass structural shell,” including shell collapse, leaks through the shell, or “separation between the acrylic surface and the shell caused by faulty bonding.” It excludes micro-abrasions, pinholes, sun-related surface changes, and damage from misuse, heavy impacts, poor maintenance or chemical abuse. If you see a blister or crack, photograph it and contact the maker or dealer before any repair. If you are shopping secondhand, our used vs new hot tub checklist covers shell inspection.
Frequently asked questions
What are hot tubs made of?
Most hard-sided hot tubs have an acrylic shell reinforced with fiberglass or ABS inside an insulated cabinet. Others use rotomolded plastic, vinyl liners, inflatable PVC, wood or metal.
Acrylic vs rotomolded hot tub: which is better?
Per Hot Spring, acrylic is glossier, holds heat better when insulated and costs more, while rotomolded tubs are lighter, matte and cheaper to buy but less efficient to heat.
Do you sell inflatable hot tubs?
Our catalog search did not return an inflatable hot tub. We carry the Tru Grit Fitness inflatable ice bath, which uses a PVC shell, for cold plunges.
Can I use household cleaner on an acrylic shell?
The Arctic Spas manual says no: skip household cleaners, alcohol, abrasives and solvents, and use a soft cloth, baking soda or vinegar. Check your own tub’s manual.
Questions about a specific shell? Call us at 866-777-2590, Monday to Friday, 9AM to 6PM PST. Shipping is free freight on orders of $999 or more, and $200 flat below that.
