Do I Need Sand Under Concrete Patio?

As the colourful sails flutter on the blue canvas of Auckland’s Waitematā Harbour, they lay testament to the city’s close-knit relationship with preparation and foundation – whether it’s to navigate the challenging Hauraki Gulf waters or lay a sturdy concrete patio in the backyard of your Grey Lynn villa.

To answer your question: yes, a layer of sand or a similar aggregate is often required under a concrete patio, and here’s why.

In the context of Auckland’s weather, which can swing from bright sunny days to sudden downpours, having a sand base beneath the concrete slab provides several advantages. The sand layer helps with water drainage during wetter periods, preventing water from pooling beneath the concrete and causing potential issues such as hydrostatic pressure or frost heave.

Sand is also very useful for achieving a flat, smooth base. Just as the landscape architects levelled the grounds of the Auckland Botanic Gardens, laying sand under a concrete patio allows for easier levelling and compaction. This can help prevent any uneven settling that may lead to future cracks in your concrete.

Moreover, in areas with clay soils, typical of certain Auckland suburbs like Mangere or Otara, sand can create a buffer between the expansive clay and the concrete, reducing the potential for soil-related swelling and shrinking to affect your patio.

However, there are certain factors to consider. The type of sand and its compaction are critical. Poorly compacted sand can shift over time, leading to an uneven patio. Therefore, using well-compacting, coarse sand, and ensuring it is compacted thoroughly, can provide a robust base for your concrete patio.

Like meticulously preparing a yacht for the Royal New Zealand Yacht Squadron, ensuring the right preparation for laying your concrete patio, including the right kind of sand base, will help you sail smoothly into many years of enjoyment on your new outdoor space. So, whether you’re preparing for the America’s Cup or your backyard renovation, remember – the secret is in the base!

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