Liquid screed

Have you ever walked on a tiled floor in a building in Bristol, or for that matter anywhere else, only to notice that some of the tiles have cracked? It can happen, but why? The answer is simply that the surface upon which the tiles were laid was not level, because whoever carried out the contract failed to use a floor screed in Bristol. It must have had dips and bumps in it, with the result that when a weight, such as that of a person, is put on the tile it is almost certain to crack in some places in the room.

There is an answer to this problem, although it is too late to do anything about the room we just described, other than rip up all the tiles and start again – which would be a very expensive procedure – and that is that when constructing a building you should always use a layer of floor screed over the substrate for the precise purpose of having a flat surface on which to fix the final flooring – whatever it is going to be.

So, what exactly is a floor screed? For many years it was simply a mixture of sand and cement in a ratio of 1.3 to 1.45 cement to sand which was laid on the substrate and then levelled out by a worker on hands and knees using a trowel. The sand and cement mix would be produced using a simple cement mixer on site and then barrowing it on to the substrate.

Unfortunately, this has certain issues, one of which is that it is impossible for the mix to be consistent for the simple reason that workers are shovelling the sand and cement into the mixer – and they are not weighing each shovelful! This is the reason that today, on the larger building sites, they use ready mixed screeds which will be consistent.

A Lengthy Process

Another issue is the time that it takes for a labourer on hands and knees to level out the screed. It is a very lengthy process, and this can have the effect of causing delays on the contract which, depending upon the size of the floor area, can take days, or even weeks.

Not only that, but there are other issues when it comes to installing underfloor heating. This is becoming much more popular these days. Until recently, underfloor heating was only installed in high-end homes, but it has several benefits for any home or other building because it heats the room evenly.

There are two types of underfloor heating – either electric or water-based. Electric heating comes in the form of either a heating cable, or a cable fixed into a heating mat. Both are quick to install, but expensive to run because electricity tariffs are high and only going to get worse. A water-based system can be heated using your boiler or an air-source or ground-source heating system, or solar heating panels. For this reason, electric underfloor heating is usually only used in small rooms such as a bathroom, not larger ones.

However, when you install underfloor heating which is water-based you have to run the pipes under the floor, and this requires a floor screed in order to cover them and protect them and upon which to lay the final floor surface.

Liquid Screed Has Several Advantages

Today, we also now have liquid screed in Bristol which has several advantages over old-fashioned sand and cement screeds.

  1. A liquid screed can be laid far thinner than sand and cement, and this means that it will require less energy to heat the room, so there is a saving on heating bills.
  2. When you are using a sand and cement screed and laying it by hand with a trowel, it is almost impossible to fully cover the heating pipes. What this means is that there will be gaps and voids in places around or under the heating pipes and so the heat transfer into the room above will not be even.
  3. Liquid screed is made from sand and calcium sulphate which is used as the binder in place of the cement. Because the screed is in liquid form it is delivered to site ready mixed and pumped into place using a pump and long hose connected to the delivery truck. Since the screed is liquid, it flows around the heating pipes and totally covers them, so there are no voids or gaps anywhere. That means that heat transfer into the room is perfectly even.
  4. Better still, a liquid screed in Bristol – or anywhere else – has almost twice the thermal conductivity of sand and cement, so again this means that the heating system will need less energy to achieve the same temperature in the room. While a water-based underfloor heating system takes longer to install than an electric one and is more expensive, once it is up and running, the energy savings that are obtained when used in conjunction with a liquid screed will go on for as long as the building lasts.

It is also the case that liquid anhydrite screeds cost more than sand and cement do, but this is evened out by the fact that you don’t need so much material because it is being laid more thinly. Another very important thing to take into account is the fact that the screed is so quick to lay.

Liquid screed installers will tell you that they can pour up to 2,000 square metres of their anhydrite screeds in a single day. This is up to 20 times as fast as laying a sand and cement screed by hand! It follows that the labour cost of using a liquid screed in Bristol is far, far less than sand and cement.

Furthermore, a liquid screed will actually be dry enough to walk on within 24 – 48 hours after being poured into position. What that means is that other contractors who need to work on the site are not going to be unduly delayed, which is what can happen when you lay a screed by hand.


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