What is the difference between concrete and screed?

If you’re new into the world of screeding – you may be wondering what the difference between a screed and concrete is! After all, they do essentially have the same ingredients – cement, aggregates and water. So what makes them different?

In simple terms the key difference is this:

Concrete has the potential to hit a very high strength. A screed is used simply, as a top layer or finish.

How do I tell the difference before they set?

One of the key differences between concrete and screed is the texture. This isn’t something that many people will notice initially – or be able to measure to the untrained eye.

Concrete has a rougher texture than screed because it contains aggregate and stones – as well as sand and cement. These small stones are typically 20mm or less and are easily visable in the concrete when it is liquid. This is what makes concrete the stronger material.

Screed is a type of mortar. It is a smoother mixture made from sand and cement, a soil-type substance and it does not have the gravelly aggregate, the maximum grain size is around 4mm for a dry screed. This allows for a finer grain appearance when compared to concrete in its liquid form.

It’s been laid already! How do I tell the difference now?

If the surface has already been laid and the surface has hardened, the texture may not be easy to determine. You will need to look at the method used to lay it and the location of the material to make an educated guess.

Screed is most commonly used as a finishing layer on internal floors, with a thickness of around 50mm to 100mm.

If the surface was laid using floats – it is probably concrete. Concrete is usually laid much thicker, a minimum thickness is 100mm is recommended for domestic use and up to double that thickness for areas which have heavy footfall.

Concrete and screed can both be used for flooring and with underfloor heating – but it is highly unlikely that a DIYer would lay concrete in their home without the help of a professional.

A lot of modern homes do have polished concrete and this is something which can be purchased in a pre-polished state.

Getting concrete advice

Additives, commonly known in the trade as admixtures, are materials which can be added either before or during the mixing process to alter its properties. Admixtures can allow for various functions of the product depending on the requirements of each individual job. The admixtures can be categories within their functions to include bonding, shrinkage reduction and damp proofing.

Using admixtures can help when laying either concrete or screed. They can do a number of different things such as speed the setting time up. Fibres can be added to the screed to help reduce the cracking and retarder to give you more time to work with the screed.

At Tekfloor we would be happy to advise any concerns you may have about the concrete or screed – please contact us and speak to one of our technical experts.