Pouring Concrete over an Existing Surface


Pouring new concrete over an existing surface can save time and money on home renovations and outdoor restorations.

But it could compromise the lifespan of your new concrete surface.

One of the most commonly asked questions Geostone receives is: ‘can a polished concrete floor be laid over an existing slab or floor tiles?’

We encourage all of our customers to discuss their individual circumstances with their concrete installer, but the short answer is, it can be done – sometimes.

Digging up old concrete is a difficult and usually costly exercise, which is why so many people seek to simply cover it up.

But it’s important to remember the new layer of concrete will only be as stable and durable as the original slab underneath.

Geostone is a decorative concrete product, not a concrete overlay, but in some cases it can be used on top of an existing surface.

A well-laid concrete slab has an expected lifespan of up to 40 years, but pouring new concrete over a cracked, sunken or damaged slab means it might not last as long.

While pouring concrete on top of an existing surface could save money in the short term, you need to weigh up the risks with your installer to determine if it will pay off in the long run.

Reinforcement is also recommended when pouring concrete on top of an existing concrete surface.

This instructional video suggests using a layer of sand between the two slabs and installing steel reinforcement bars before pouring the concrete.

Using sand between the two layers allows both slabs to expand and move independently, helping to prevent cracks and damage to the top layer.

As the popularity of polished concrete floors rises, a growing number of homeowners are also seeking to cover up old floor tiles.

According to Concrete Network, this can be done, but again precautions should be taken to ensure the existing surface is up to the task.

They only recommend pouring concrete over existing tiles if they are in sound condition and firmly affixed. Glazed or textured tile surfaces should first be sanded back to ensure a good bond with the concrete, wide grout joints should be sealed to avoid obvious outlines and sinking, and several coats of primer should be used to prepare the site. Again, this will depend on the recommendations of your concrete installer for best practice placement.

Another consideration is the height and depth of your concrete surface. Pouring concrete onto an existing slab or pathway will result in a concrete surface several inches higher than before. This could prevent doors from opening and closing, cause misalignment with stairs or even create a trip hazard, so consider these issues when planning your project.

Concrete poured on top of existing surfaces should be monitored and maintained. Any damage should be patched promptly to prevent spreading, and sealed to avoid water damage.

Signs that concrete may be becoming unstable include small cracks or water pooling on the surface. Patching cracked, sunken or damaged concrete usually only requires a thin coat of concrete, while more significant restoration will require a thicker coat.

Whether you decide to pour concrete over an existing surface, or start from scratch, Geostone provides durable and long lasting decorative concrete solutions with warm and welcoming appeal.

The Geostone range of exposed aggregate, coloured concrete  and polished and honed concrete is available in an assortment of colours, featuring natural Australian stone unique to your local area. This gives you the creative control to choose decorative concrete customised to suit your home, colour scheme and personal style.

For more information about Geostone and concrete you can browse our blog or contact us today.

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