Did you know that the type of floor screed specified could have a big effect on the building process and final result? So make sure that you are aware of the type of screed to be used and its pros and cons. Here are some factors to consider but first let us brush up on our screed definitions!

Traditional or sand/cement screed is a manually laid semi-dry product, either mixed on site or delivered from a factory.

Liquid or flowing screeds are delivered in a truck mixer and pumped in to the development. They fall in to two categories, anhydrite based and cement based.
In this article, we talk about the advantages of using a liquid floor screed.

Installation time:

The installation of a liquid floor screed is much lower because it is less labour-intensive compared to a traditional applied on your hands and knees floor screed. Since liquid floor screeds are pumped and simply “dappled” from an upright stance they are much faster to lay. For a typical house the whole screed pour and levelling process will only take a few hours. Liquid floor screed can cover up to 1000m² in one day

Quality:

A liquid floor screed will have a more even surface than a hand laid semi-dry traditional screed and because it is denser sound is deadened and heat transfer speeded up. Better heat transfer (aka increased thermal conductivity) can be advantageous when underfloor heating is in place. Anhydrite screeds are even more thermally conductive than their cement equivalents.

Low shrinkage:

Another great advantage of liquid screed is that it does not shrink or curl. This is true of both types of flowing screeds, cement and anhydrite based.

Drying times:

Long drying times can be are a problem in a build programme. If drying time is important you need to carefully consider which flowing screed to use. Anhydrite based screeds dry at about 1mm of thickness per day up to 40mm thickness, thereafter at half that rate. So a typical 50mm deep anhydrite screed takes 60 days to dry before tiles or other floor coverings can be applied. A cement based screed dries out at a third of that time – say 20 days for a 50mm thick floor.

Both anhydrite and cement based liquid screeds are typically OK to walk on after 24 hrs.

Use with concrete:

One of the advantages of traditional screed was that when applied over concrete or under cement based adhesives there was no risk of a chemical reaction causing the two surfaces to pull apart from each other. The same advantage is enjoyed by cement based liquid screeds.

However if using an anhydrite based screed there is a risk if the anhydrite screed has not been allowed to thoroughly dry out in line with the manufacturer’s instructions.

Use in wet rooms

Received wisdom is not to use anhydrite based screeds over wet rooms and in potentially wet areas. If water penetrates in to the screed it will soften, expand and lose strength.

Longfloor is a dry powder bulk binder for the manufacture of a cement based liquid screed. A family-owned independent company, it is the second largest industrial grade limestone powder manufacturer and supplier in the UK If you want to have liquid screed installed, don’t hesitate to contact us. Send us an email at sales@longfloor.co.uk or call us on 01629 540 284. Our friendly team is always eager to help. You may also continue browsing our website to know more about our products and services.