When you are laying a floor in a new building, one of the major considerations is surface regularity. Sub floors are usually constructed of concrete, and this will have variations in depth, and therefore produce a surface which is not level. This is certainly not ideal for laying the finished flooring on, whatever type it is going to be.
So, in most buildings, it is necessary to lay a floor screed on top of the substrate in order to try to achieve as level and flat a surface as possible upon which to lay the final flooring. Traditionally, a floor screed has been made using sand and cement mixed on site and trowelled on to the substrate by a labourer on hands and knees.
This has certain disadvantages, not the least of which is that no matter how skilled the labourer, the surface is unlikely to be as flat as it could be. The “levelness” or “flatness” of a floor surface is measured according to British Standards and is referred to as Surface Regularity. The three standards are SR1 which is High Standard, SR2 which is Normal Standard, and SR3 which is Utility Standard.
In order to achieve SR1, the surface must have a variation of no greater than 3mm measured over a distance of 2 metres. SR2 allows for up to 5mm, while SR3 allows up to 10mm.
The measurement is obtained by laying a straightedge over a 2-metre distance and measuring any gaps underneath it with a slip gauge.
Unlikely To Be Better Than SR3
Now a floor screed made up of sand and cement is unlikely to achieve a surface regularity any better than SR3, which is not as level as it could be. Hence the reason why liquid floor screeds are becoming so much more popular for new builds, especially when underfloor heating is being installed.
If you lay a liquid floor screed in Wokingham, or wherever the project is being constructed, it is not mixed on site, but is delivered to the site ready mixed. A pump and long hose are connected to the truck and then the screed is simply pumped on to the substrate. This is a very quick process, and it is quite possible to cover the substrate of the whole ground floor of a house in an hour.
Most importantly, because it is in liquid form, it levels itself out. This is just the same as if you poured water into a flower vase, for example. In half a minute or so, the surface of the water will be flat.
When laying a liquid screed, all that the contractor has to do is to run over it with a dappling bar after it has been poured, just in order to remove any air bubbles, and then leave it to dry – which only takes a maximum of 48 hours, and often less.
Because the screed is liquid, it will always achieve SR2, and in most instances SR1, which provides as level a surface on which to lay the final flooring as you can get.