When you are laying a floor screed in High Wycombe, you have a choice of the traditional sand and cement screed or the 21st century variety which is a liquid screed. The latter has many advantages over and above the older mix, not the least of which is the speed of laying.
A sand and cement screed is usually a relatively strong mix of 1:3 cement to sand which is often mixed onsite in a cement mixer. This is barrowed on to the subfloor and then levelled out by a worker on hands and knees using a hand trowel. Mixing in a cement mixer just by shovelling in the relative materials does mean that there will be some inconsistency in each load, and so today, certainly on larger contracts, the screed will be delivered to site ready mixed. The process of laying and levelling is the same though.
The alternative is liquid screed which is a mix of sand and anhydrous (dry) calcium sulphate which becomes gypsum when water is added to it. At UK Screeds, we deliver this to site ready-mixed. Because it is in liquid form it is not barrowed on to the substrate. Instead, we connect a pump and a long hose to the delivery truck and simply pump it on to the floor. Our teams can cover an area of 100 square metres in about 45 minutes and lay up to 2,000 square metres in a full day.
20 Times As Fast
Once the screed has been poured to the required level, we just go over it in two directions with a dappling bar which will remove any air bubbles. We then leave it to dry. This is up to 20 times as fast as a worker can level out a sand and cement screed.
Depending upon the weather conditions, this will be dry enough to walk on within 24 – 48 hours. The big advantage here is that there is no delay to other contractors who also need to work on the site.
Liquid screed costs about 50% more than sand and cement, but this is offset by the fact that it can be laid thinner, so not as much material is needed. The screed can typically be laid to 35mm. With underfloor heating, you will need 30mm above the heating pipes making a total of 45mm which is still incredibly thin. (A sand and cement screed in conjunction with underfloor heating will usually be at least 75mm and often over 100mm). This also assists in the drying time. In addition, the speed of laying also means that the labour cost is considerably reduced.
When you are installing underfloor heating, there is another big advantage to liquid screed. This is the fact that it will totally envelop the heating pipes leaving no gaps or voids. That is almost impossible to achieve when laying a sand and cement screed by hand. The result is that the heat transfer into the room is 100% even with a liquid screed, which is unlikely to be the case with the alternative.