Over the last five or six years there has been a considerable increase in the use of liquid floor screeds instead of traditional sand and cement. Indeed, it is estimated that liquid screeds now account for some 20% of all floor screeds laid, and that figure is increasing all the time.

There is no law that states that you must cover your ground floor substrate with a screed, and indeed a screed is not structural. As an example, in garage conversions it is often the case that floorboards are laid over thick sheets of insulation. However, the fact is that screeds are very good at providing a level surface on which to lay the final flooring, and it is this surface regularity, as it is called, which ensures that there are no problems with the final flooring. For instance, laying tiles or stone on a surface that is not level will cause them to move and crack, which is the last thing that you need.

Using a screed is particularly important if you are using concrete beam and block flooring because it has a definite camber which can give you problems when it comes to laying the final floor surface. Liquid screeds are also very useful when it comes to laying underfloor heating pipes because they cover the whole area leaving no gaps. They also have almost twice the heat transfer ability of a traditional sand and cement screed, which results in a completely even transfer of heat throughout the floor and also uses less energy in order to produce a given level of heat. So from an environmental point of view they will go on paying for themselves for as long as the floor lasts.

Conventional sand and cement screed is traditionally prepared on site, but using a cement mixer is very labour intensive and also can vary from batch to batch. Most larger sites now use ready-mixed sand and cement screeds delivered to site by lorry and containing retardants so that they can be used for longer. However, there is still the issue of laying the screed by hand which is also very labour intensive, whereas a liquid screed is delivered to site ready-mixed and can be pumped into place at far faster rates than can ever be achieved with a traditional screed. Some providers claim to be able to screed an area of 100 square metres in 45 minutes, and as much as 2,000 square metres in a day.

Some of the terminology around liquid screeds can be confusing because they are variously referred to as liquid screeds, anhydrite screed, self-levelling compounds, calcium sulphate screed, gypsum, flowing screeds, and so on. Then there are brands such as Gyvlon, which is also a liquid screed. The chief ingredient is anhydrous, or dry, calcium sulphate which normally has around a third of recycled content in it. This is a by-product of the chemical industry which would otherwise go to landfill, so is environmentally friendly from that point of view as well. When calcium sulphate is mixed with water it produces gypsum which is used as a binder instead of cement.

If you are considering using a self-levelling compound in Gloucester, there are some things to note. First is that the material itself costs more than sand and cement. However, because it is poured and laid so fast there are considerable savings on labour.

However, there is another big benefit of using a self-levelling compound in Gloucester and that is that you don't need so much of it. A liquid screed does not need to be laid to anything like the depth that a traditional sand and cement screed does. It can be applied at depths of as little as 35mm and even when using underfloor heating only 45mm in total is needed. Using sand and cement with underfloor heating can require as much as 80mm.

Liquid screed also dries fast, being ready for foot traffic in 24 – 48 hours and it is far less prone to shrinkage and cracking.

If there is a downside, it is that when anhydrite screed dries it leaves a layer of laitance on the surface and this must be removed before the final floor is laid. This can be done using floor sanding machines around six to seven days after pouring.