What Is the Best Foundation for a Spa?

Are you considering purchasing a spa or hot tub? Maybe you have already placed an order and are awaiting delivery? 

A spa can be an excellent investment for your mental and physiological health. They can help with skincare, blood circulation, stress reduction, massage tired bodies, and provide hours of entertainment and pleasure for you and your family.

If you have gone forward with your wise purchase, you have no doubt picked out the ideal location at your home, and considered how you wish to stylise the surrounding space. But what about the base of your spa? How much thought and planning has gone into your new investment’s support? And what is the best foundation material to use for my spa base?

Spa baths come in many shapes and sizes and are relatively heavy even before a drop of water is added. They can range anywhere from an intimate two-seater, to an enormous twelve seater. 

The bigger the spa, the larger the volume of water, and ever litre adds significantly to your spa’s total weight. Even a standard three or four-seater tub can hold anywhere from 700-1000 litres of water, meaning your spas could weigh well over a ton by the time it has been filled. 

Your best option may also depend on whether your tub is being installed inside or outside your home. So what is the best material to place under your spas sensitive fibreglass base? Read on to find out.

Cement slab

A cement slab is a common base for spa baths and is perfect for both inside and outside hot tubs. The cement should be poured by someone with experience in spa slabs. This ensures it has been levelled and the surface underneath is sufficient for weight distribution.

The average cement spa slab should be at least six inches thick, reinforced with rebar and sitting on a well-compacted rubble base. Generally, people make the slab slightly wider than the spa base and surround the spa with wooden decking. 

If you wish to tile around your spa, then you may want to consider getting custom formed concrete poured. It is worth considering, however, that this will make things much harder if you wish to sell your spa down the track.

Gravel beds

A bed of compacted gravel can be a great option as long as it has been correctly compacted and levelled. You will also have to ensure the ground below your gravel bed is stable and won’t shift underneath.

You must also provide adequate drainage to make sure the gravel does not get washed away during a weather event. It is also essential that you cover the gravel with steps or decking. You want to ensure means to wash your feet to avoid tracking sand and metal into your spa and damaging your pump and filter.


Wooden decking is a popular option for outdoor spas. It gives a classic hot tub aesthetic and makes it easier to remove the spa and modify the space if you decide to sell or upgrade down the line.

Quite often decking alone will not be strong enough to support the full weight of a spa. If your spa can reach the ground beneath your decking, then you may still require compacted gravel or a concrete slab to support the filled hot tub.

If you do require your spa to be supported by decking, the odds are you will need to consult a builder or carpenter to modify the decking and engineer a sufficient support structure. 

Concrete pavers

Cement pavers offer plenty of support for the weight of your spa so long as they have been laid on a solid foundation. Most pavers are levelled on a base of heavily compacted sand and metal followed by a layer of paving sand.

You must be sure that this is the case if the pavers are going to support such a substantial body of water. The bottom of most spas are also uneven, so you may still need to use gravel or concrete to contour around the base of the hot tub.

Hot tub pads

These rubber pads are specifically designed for the installation of spa baths and can be a more affordable option than concrete slabs in many circumstances.

The pads interlock together on a bed of gravel. The pads cavities are then also filled with gravel or pea shingle and compacted down again. This product creates a very robust and stable base for your spa. It also offers maximum protection from erosion in severe weather.

One major manufacturer even boasts a support weight of up to 420 tonnes per square meter! These pads are also perfect for both indoor and outdoor applications.

Do you need reliable advice on creating a solid foundation for your spa? You can contact the award-winning team here at Ezy Spa. We specialise in delivery and removal services for spas and hot tubs. This includes pre-sale inspections and supplies for a wide range of quality spa care products.

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