Polished concrete floors are becoming increasingly popular in homes, with a range of finishes and colours meaning they can be specified in colours other than grey. But even those who love the look might have questions about their practicality and uses. Read on to find out more.

Quick Facts About Concrete Floors:

  • These floors are diamond ground and then treated with a chemical densifier.
  • They are polished with diamond-polishing tools, using polishing pads specifically for using on concrete.
  • Polished concrete will most commonly be finished to a grit level of 800, 1,500 or 3,000 depending on the level of shine required.
  • Concrete is not considered polished before 400 grit. This is called ‘honed’ concrete.
  • Polished concrete floors are best designed in early on in a project.
  • They are most commonly 100mm thick.
  • They often tend to be specified with underfloor heating.

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How Much Does a Polished Concrete Floor Cost?

You should expect to pay anything upwards of £115/m² to include the placing, finishing and sealing. This will depend on the size and type of floor you choose to have, and even adverse weather conditions can have an influence on your choice.

What is it Like to Live With a Concrete Floor?

Polished concrete is hardwearing, easy to clean, improves with age, will not harbour dust mites and provides a neutral backdrop for your interior design scheme. It can be used inside and out for a continuous floor scheme, but be aware that it will weather outside, affecting colour and appearance. Any damage that does occur can be removed with repolishing if needed.

On the downside – and this may sound rather obvious – it is incredibly hard, so if you fall or drop something on it, concrete will not be the most forgiving of floor coverings. It also tends to be quite cold underfoot — although combining it with underfloor heating will easily solve this issue.

You should expect some hairline cracks in the floor and for the floor to be slightly lighter in colour around the perimeter. Some maintenance is required, and the floor may need resealing over time. Suppliers offer a range of stain-removal treatments and aftercare products too. Any spills (especially acidic liquids) should be mopped up as soon as they happen.

Polished concrete floor in a small urban home

Polished concrete floors and whitewashed timber walls act as a backdrop to the rich tones of the hardwood joinery in this compact urban self build

How is it Installed?

It is unwise to attempt the pouring and polishing of a concrete floor on a DIY basis — the skills, equipment and the experience required make this a specialist job.

The most common way for a domestic floor to be poured and finished is using the ‘flooded bay’ method:

1. “The whole space is filled and levelled using a laser, rakes, vibratory screeding machines and bull floats.

2. Over the course of the day, the concrete surface is refined and flattened using hand floats and power floats.

3. The final surface is closed off and densified by hand trowel and/or power trowel machines. This brings the cement paste to the surface, smoothing and hardening it until it develops a sheen. This can take anywhere from four to 14 hours, and is partially dependent on the weather conditions — too cold (5°C or lower) and fresh concrete can be permanently damaged; too hot and there is a risk of the concrete shrinking.

4. Once poured and prepared, the concrete will need to be polished and sealed — something that must be carried out at least a month after pouring.

5. Polishing either comes from cleaning and buffing the floor with a scrubbing machine or, better still, light diamond polishing to remove minimal laitance to bring out a medium sheen. For highly polished floors, the surface can be further enhanced using diamond-encrusted flexible buffing pads.

6. The floor will then need to be sealed. A penetrative sealant that allows the concrete to breathe is used.

Can You Retrofit it?

Polished concrete floors can be fitted into existing properties, but they are more usually specified for extensions. However, it is possible to replace a suspended timber floor with concrete — just bear in mind that the finished floor levels will need to be built up fairly considerably in order to maintain the original floor level.

Ventilation will also need to be taken into consideration, although if the new concrete floor is to be suspended rather than supported by the ground, then a block and beam system can be used, in which case a structural engineer would need to be consulted.

Who Supplies the Concrete?

The concrete for the floor can either be supplied by a ready-mix supplier, or ‘site batched.’

  • Ready-mixed concrete is a more cost-effective solution.
  • Site-batched concrete is ideal for smaller areas, but it tends to be a slower process. On the upside, there is no need for a pump and this method allows for more choice in terms of aggregate types and the use of integral pigments, or white cement for example.
Polished concrete floor in a remodelled London Terrace

The floor of the main living space is polished concrete in this remodelled Victorian terraced house

Are They All the Same?

In most cases, polished concrete comes in the form of a 100mm-thick screed. However, it is also possible to specify the finished floor as a ground-bearing slab, which is usually a minimum of 150mm thick and comes with heavier reinforcement.

The floor is poured onto well-compacted MOT Type One (an easily compacted aggregate), blinding sand, DPM (damp-proof membrane) and insulation. A polished screed already has the ground-bearing slab in place and is poured over the insulation sitting on the slab below.

So, which one do you choose? The polished ground-bearing slab has the added advantage of producing the finish in one go, but will have to be poured earlier and may suffer damage as other heavier work is carried out afterwards.

When is Polished Concrete Installed?

When building from scratch, or using polished concrete for a new extension, the majority of in situ polished concrete flooring is put in place prior to doors and any door tracks which may be fitted.

It is possible to produce the floor with these elements in place, but there is a great risk as cement corrodes aluminium and the process is not delicate. Doors can also cause a hindrance to the contractor and not allow for threshold details to be incorporated.

A 10mm-thick brick-foam material is fitted to the perimeter of the floor to allow for any movement. This needs to be hidden by skirting or similar, so the floor must be poured before this stage of decoration too.

In the case of shadow gaps, recessing it behind the wall build-up will hide the expansion material, and the floor should then be poured before the final wall finishes are built out.

Any partition walls, kitchen units, etc., should be constructed on top of the finished concrete floor.

Thanks to Jonathan Reid of GreyMatter Concrete for advising on this piece.


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