When constructing any sort of building, there are many things to take into consideration, but one of the important ones is the levelness, or otherwise, of the flooring. The final flooring, which is going to be walked upon, and in the case of something such as a warehouse may also have to carry things like forklift trucks, needs to be as flat as possible.
Laying the final flooring straight onto the concrete substrate is never going to produce a floor that is as level as it can be, and so the answer is to cover it with a screed which can produce a much more level surface.
For many years now, the traditional screed that has been laid on the concrete has been made of a mix of sand and cement usually in the ratio of one part cement to three parts of sharp sand. Usually, this would be mixed on-site by simply shovelling the materials into a cement mixer, but this is very labour intensive and produces an inconsistent mix, with virtually every mixer load being slightly different from the last one.
The screed mix is then barrowed into the building and laid out and levelled by a worker on hands and knees using a trowel. Apart from any other considerations, this is extremely time-consuming and causes delays in the construction process because the screed cannot be walked upon until it has been finally finished and has dried off. Depending upon the area to be screeded, laying it could take several days, so other trades such as plasterers, door fitters, painters and decorators, and so on, just have to wait until the screed is ready.
Not only that but laying a screed by hand in this way is never going to produce a totally level finish. The regularity of the surface, which is often described as the waviness of it, is measured based upon the amount of deviation under a straightedge laid upon it over a distance of two metres. This is described as the Surface Regularity and is described as SR1, SR2, or SR3, depending upon the amount of gap measured by a slip gauge.
SR1 is High Standard, SR2 is Normal Standard, and SR3 is described as Utility Standard. To achieve SR1, the maximum gap measured by the slip gauge must be no greater than 3mm. For SR2 it is 5mm, and for SR3 10mm. When laying a traditional sand and cement screed by hand, SR3 is the most likely result since it is almost impossible to achieve even SR2.
However, the good news is that over the last few years new screeds have been developed that are in liquid format, and which have many advantages over sand and cement, and this is the type of screed that we lay at UK Screeds. If you are looking for a liquid screed company for hire in Bristol, we are here for you.
Our liquid screeds are made up using calcium sulphate instead of cement and are delivered to site ready mixed. This means that the screed is going to be of a regular consistency. On arrival, we lay the screed using a long hose and a pump. Since the screed is liquid, it is pretty much self-levelling, and because it is pumped into position it is far quicker to lay than sand and cement by hand. In fact, it is reckoned that we can lay a liquid screed up to 20 times faster than a sand and cement screed laid by hand. We can regularly achieve an area of 2,000 square metres in a single day.
Once the screed has been poured into position, we then simply agitate it with a dappling bar in two directions in order to remove any air bubbles or tide marks. The screed is then left to dry, but this only takes between 24 and 48 hours before it is safe enough to be walked on. That means that there is a minimal delay to other contractors who need to work on the site.
During the drying period, direct sunlight must be avoided, so doors and windows must be kept shut, and covered if they are south facing. After this, other work can carry on as normal.