HOW TO BUILD A CONCRETE SLAB - tips on building a solid foundation for your spa, swim spa or plunge pool
A solid foundation
Once you have selected a site for your new spa, ensuring there is the suggested 600mm clearance all around, you’ll need to prepare a solid, level foundation which will remain stable for the life of your spa.
A typical spa in use poses a considerable weight for any foundation to support. Even our smaller spas can weigh up to 2000kg when filled with water and occupants, some of our larger models can reach 3000kg and our swim spa up to 7000kg.
Refer to your brochure or our website for dimensions and approximate filled weights of Sapphire Spas models. For example, the specifications on myChillout spa page (https://www.sapphirespas.com.au/spa-pools/mychillout) show that it weighs 1535kg when full of water plus the weight of the people in the spa. Remember, weight of occupants must also be considered in addition to these figures.
Do not put your spa on any soft surface such as grass, sand, pebble or dirt as this may place undue stress on your spa, causing it to distort and/or crack.
Damage caused by an inadequate foundation will void the warranty on your spa. It is the owner’s responsibility to ensure correct installation of the spa.
Whether choosing a concrete slab or timber decking to support your spa pool, Sapphire Spas strongly recommend the use of a licensed contractor.
Sapphire Spas recommend the best way to provide a solid foundation which has an even, level surface, free from cracks or hollows, is with a concrete slab.
CONCRETE SLAB - tips on building a solid foundation for your spa, swim spa or plunge pool
A reinforced concrete slab of at least 100mm thick is a suitable foundation for your spa; this must be increased to a minimum of 150mm thick when installing swim spas. You must ensure this base is an even, level surface free from cracks, doming or hollows. No fall / gradient is to be present within spa footprint; the concrete surface should be finished with a perfectly flat screed.
SPA POOLS (up to 3500mm in length) - minimum 100mm thick concrete slab / 1 layer of steel reinforcing mesh
SWIM SPAS (4000mm+ in length) - minimum 150mm thick concrete slab / 2 layers of steel reinforcing mesh
SIZE OF SLAB
It’s preferable for the slab to extend at least 200mm outside the spa dimensions for stability.
Your tradesman will prepare a level surface, large enough to extend approximately 200mm on all sides of your spa cabinet dimensions. This will help to provide stability and prevent cracking of the concrete. The space which will be required for the footprint of your new spa will need to be scraped to level out by removing any uneven grass, debris and clumps of dirt.
After the initial ground preparation, rock is usually added to the prepared dirt area, to provide stability, prior to the concrete being poured.
LEVEL SPA FOOTPRINT
No fall / gradient is to be present within spa footprint; the concrete surface should be finished with a perfectly flat screed.
If you pre-power through concrete to conceal the electrical connection, the concrete surrounding the conduit needs to perfectly cleaned so no raised areas are possibly going to interfere with the spa base as it’s positioned over the electrical conduit
Always check with local conditions but these are minimum suggested specifications for concrete spa and swim spa slabs
- minimum 100mm thick
- 1 layer of SL72 steel reinforcement mesh positioned as per diagram
- suggested 25mpa concrete mix
- minimum 150mm thick
- 2 layers of SL82 steel reinforcement mesh positioned as per diagram
- suggested 25mpa concrete mix
If you want to create any fall/gradient across the slab, it needs to be outside the spa footprint. There entire area on which the spa cabinet rests, needs to be flat and level; no slope or gradient is acceptable as this may cause the spa frame to warp and twist thus voiding warranty
Any drainage channels need to be installed outside of the spa footprint (see diagram)
WE'RE HERE TO HELP
We hope this information has now prepared you to liaise with your concrete tradie to construct a level, even slab to adequately support the weight of your new spa. Any movement due to inadequate foundations may place unnecessary stress on the acrylic shell or cabinet, possibly causing damage which can not be covered by warranty.
All work is to be conducted within the constraints and recommendations of your local building authority.
If you have any questions, please just ask your local spa retailer or call the Sapphire team on 1300 069 772 for advice on a stable foundation for your new spa purchase which will provide trouble free enjoyment for many years to come.
Sapphire Spas recommend that you consult a structural engineer to ensure that your decking is capable of safely and adequately supporting the full weight of your spa when in use. Should you wish to surround your spa with decking, we suggest that you install it on a concrete slab (as above) then build the deck to surround your spa.
SAPPHIRE SPAS WILL TAKE NO RESPONSIBILITY FOR THE INSTALLATION OF YOUR SPA