A solid foundation for your spa – what you need to know

Your spa, swim spa or plunge pool needs a solid, flat, level foundation. lt must be positioned to allow for adequate service access on all sides of the spa. Learn more in this article.

spa foundation hero

If the foundation of your spa, plunge pool or swim spa is inadequate – it may shift or settle after the spa is in place. This can cause stress to the shell and cabinet, which will void the warranty.

Always consult your building professional for advice about your specific circumstances. All work needs to be carried out within the guidelines of your local building regulations. Refer to your spa model's technical sheet for weights and dimensions. You can download the techpack from the specifications section of the product page for your spa model on the Spa World website.

What foundation are you using for your spa?

The five most common foundations for spas are:

  1. Concrete slabs
  2. Paved surfaces
  3. Inground spa pits
  4. Wooden decks
  5. An existing surface

Depending on the foundation you decide on, there are some rules of thumb to follow – as we explain below.

Can I use an existing foundation for a spa pool or swim spa?

The short answser is, yes provided that the foundation meets certain requirements to adequately support the weight and dimensions of the new installation.

An existing foundation for a spa pool or swim spa refers to a pre-existing base or structure upon which the spa can be placed. This foundation could be a part of an older spa setup that you intend to replace or repurpose, a section of a patio designed for outdoor leisure activities, or any other type of sturdy surface that was previously constructed for different uses.

If you are planning on using an existing foundation, you will need to make sure the foundation is adequate to support the full weight of a the spa.

We recommend consulting with a building professional to determine the structural integrity of your existing foundation and to help you if the slope is an issue.

If there is significant slope in the foundation, the spa water will not be level in the spa and this can damage the shell.

Here is an example of one solution for a sloping foundation surface:

pad slope diagram

What is a concrete slab for spa pool and swim spa installation?

A concrete slab is a common and sturdy foundation option for a spa pool or swim spa. Essentially, it's a flat, horizontal surface made of cast concrete. To create a concrete slab, a specific area where the spa will be installed is cleared, leveled, and sometimes a gravel base is laid down for drainage and stability.

A wooden form is built to contain the concrete in the desired shape and size, and then steel reinforcement, such as rebar or mesh, is often added to provide additional strength.

The concrete mix is poured into the form and is carefully leveled off to ensure a flat surface. After pouring, the concrete must cure, which can take about 28 days. Once cured, it provides a permanent, level, and strong foundation that effectively distributes the spa's weight across its surface.

How thick does a concrete slab need to be for a spa pool?

For portable spas up to 3.5m, a reinforced concrete slab with a minimum thickness of 100mm is required to ensure adequate support and stability.

Click the button below to view generic spa slab design for portable spas.

How thick does a concrete slab need to be for a swim spa?

For swim spas and spas larger than 3.5m we recommend a 150mm slab with 2 layers of reinforcing mesh.

Click the button below to view generic spa slab design for swim spas and portable spas larger than 3.5m.

Can a spa pool or swim spa be placed on pavers?

Paved surfaces like brick or stone pavers can also serve as an attractive foundation for your spa. The key with pavers is to ensure they are laid over a well-compacted base of sand or gravel to prevent movement and settling.

It's important to choose pavers that can withstand the weight and are level to avoid stress on the spa shell. If the surface is not flat or level or capable, it will cause stress to the shell that could result in damage to the shell which would not be covered under warranty.

Regular checks should be made to ensure the pavers remain flat and stable over time.

What is an Inground Spa Pit?

An inground spa pit foundation involves creating a recessed area in the ground that is designed to accommodate the spa, resulting in the spa being at or near ground level, much like an inground swimming pool.

spa pit foundation

This type of foundation offers several benefits, including a more integrated appearance within the landscape, easier access, and typically more natural insulation due to the surrounding earth.

Can a portable spa and swim spa be installed in-ground?

Much like traditional swimming pools, portable spas—commonly referred to as hot tubs—and swim spas can also be integrated into the ground.

However, such an installation requires careful planning and preparation to ensure that the unit functions correctly and safely in its new setting.

If your spa or swim spa is going to be installed in a pit, you must consult with your local builder or contractor regarding drainage. Most likely a sump pump will be required to avoid flooding.

To learn more on how to install a spa or a swim spa in a deck or pit, including the sinking requirements, please click the button below.

Watch: Swim Spa Installed in a Wooden Deck

Can you put a spa on a wooden deck?

Wooden decks are elevated platforms constructed out of timber. When used as a foundation for spas, they must be designed to support a high amount of weight. A standard deck may not be capable of supporting a filled spa without additional reinforcement.

In assessing a deck for spa installation, you must consider the weight of the empty spa, the weight of the water it will contain, and the potential weight of the occupants.

Decks must be designed and built to local building regulations by a registered builder.

Can I place my spa on an existing surface?

Yes, you can place a spa on an existing surface, but certain conditions must be met to ensure the safety and stability of the installation.

An existing surface refers to the current state of the area where you intend to place the spa. This could be your backyard lawn, a deck, a patio, or any other surface that has not been specifically designed to support a spa.

Existing surfaces might not be suitable for a spa installation as-is, because they may lack the necessary strength, levelness, or stability. A spa filled with water and people is very heavy, and without the appropriate support, the existing surface could shift, settle, or fail.

If you are installing the spa onto an existing surface, you will need to consider the amount of fall that surface has.

We do not recommend installing spas or swim onto a surface that has more than 20mm of fall across the length of the spa. You may need to talk to a builder about wedging the spa in order to keep it level.

What is adequate spa foundation drainage?

Adequate drainage is critical for protecting a spa foundation from potential flooding and water damage. Effective drainage ensures that water does not accumulate around the spa, which can lead to soil erosion, foundation shifting, and structural damage to the spa itself.

Important note: Flood damage is often not covered by spa warranties, consult with your builder or landscaper about proper drainage.

Here are some key components and considerations for ensuring adequate drainage around your spa foundation:

  • Building Codes and Permits: Check with your local building authorities for any code requirements or permits needed for installing drainage systems.
  • Slope Grading: The ground around the spa should be graded to slope away from the foundation. This encourages water to naturally flow away from the spa area, rather than accumulating around it.
  • Drainage Systems: Depending on the location and local conditions, it may be necessary to install specific drainage systems such as French drains, trench drains, or catch basins. These systems collect excess water and channel it away from the spa area to prevent pooling.
  • Proper Foundation Materials: Using a gravel base under and around the concrete pad can be beneficial for improving drainage. Gravel allows water to pass through and be directed away from the spa foundation.
  • Gutters and Downspouts: If the spa is located near structures such as a house or gazebo, ensure that gutters and downspouts are in place and direct rainwater away from the spa area. This helps minimize the amount of water reaching the foundation.
  • Waterproof Membranes: In certain cases, waterproof membranes can be applied to the foundation or beneath it to prevent groundwater from seeping up into the spa area.
  • Landscaping Considerations: Landscape design can also play a part in drainage. Plants, grass, and other softscapes can help absorb excess water, while properly positioned hard landscaping elements can direct water flow.
  • Local Weather Patterns: Take into account your local climate and weather patterns. Areas prone to heavy rainfall or flooding may require more robust drainage solutions.
  • Maintenance: Regularly inspect and maintain your drainage systems to ensure they are free from blockages and functioning correctly.

Can the spa or swim spa be accessed for service and maintenance?

It is crucial that all cabinet panels around your spa can be accessed and removed for servicing. Specifically, careful consideration is required when installing your spa in a deck.

When it comes to warranty inspections, servicing and maintenance – it is your responsibility as the spa owner to ensure the spa’s machinery and equipment can be easily accessed.

What are the key electrical considerations when planning my spa or swim spa foundation?

If you are choosing to run the power or heat pump supply through your spa foundation, please click the button below for a full list of items that you will need to be aware of.

Need more help?

We hope this information has been helpful. If you have any questions or concerns about your spa or swim spa installation, please contact your Spa World concierge.

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