When you are designing any sort of new building project, one of the many things that you need to consider is the levelness of the floors. For many years now, the answer has been to cover the substrate with a layer of screed in order to provide as flat a surface as possible on which to add the final flooring, whatever it may be.
This is particularly important if you are going to use something such as tile or stone for the final floor surface. If there are any dips and bumps when you lay tile or stone, when it is walked upon it will crack or break unless the tile is glued on to a flat surface. Using a screed will provide a more level surface on which to tile.
For many years now, screed has been made of sand and cement which was mixed on site and trowelled into position by a worker on hands and knees. Although most larger sites now have the screed delivered ready mixed, the trowelling process is the same. This is a very time-consuming task, and this type of screed is now being rapidly overtaken by liquid anhydrite screeds.
These, too, are delivered to site ready mixed but instead of being trowelled on to the substrate, the delivery truck has a hose and pump connected to it and the liquid screed is simply pumped into position. This is obviously a far quicker job than trowelling a screed into position by hand.
These screeds are made using anhydrous (dry) calcium sulphate as the binder, and when this is mixed with water it becomes gypsum. Such screeds are also, therefore, known as gypsum screeds or anhydrite screeds. Because they are in liquid form they are also known as self-levelling screeds since they do exactly that. As a liquid screed company in Gloucestershire, at UK Screeds we can lay 100 square metres of our screed in 45 minutes, and we have been known to lay up to 2,000 square metres in a day.
This is obviously a massive time saving when you compare it with laying a screed manually, and it means that there are big cost savings to be made as the labour cost is considerably less.
Now it has to be said that our liquid screeds cost more than sand and cement, although not considerably more. However, when you take the labour element into account that can make a very big difference to the overall cost.
Liquid Screed Can Be Laid Far Thinner Than Sand And Cement
Another advantage of our liquid screeds is that they can be laid far thinner than sand and cement. For example, when laid over underfloor heating the overall depth of a sand and cement screed needs to be at least 75mm and is often more. By comparison, our liquid screed can be laid at 30mm depth above the heating pipes making an overall depth of 45mm. So, there is a consequent saving on the amount of material that needs to be used.
Then there is the matter of the drying time. Our liquid screeds are dry enough to walk on in as little as 24 hours, and certainly no longer than 48 hours after being poured. This means that other tradesmen who need to work on the site are not unduly held up waiting for a screed to dry.
Although the screed is dry enough to walk on shortly after being iaid, it is not dry enough to add the final flooring. It is calculated that the full screed drying time is 1mm per day up to a depth of 40mm and 1/2mm per day thereafter. Therefore, a 45mm depth of our liquid screed will dry in 50 days.
In practice, the drying time is likely to take longer because it is based on an average temperature of 20 degrees Celsius and humidity no greater than 65%. In the UK it is unlikely that those figures could be met for such a period of time, so the overall drying time is likely to be longer. However, this can be sped up by using force drying. If the correct force drying techniques are used, it can bring the overall drying time down to as little as 28 days. Time is money, so that is another way of reducing the cost of a screed.