Liquid floor screeds have become more and more popular over the last 15 – 20 years as a flooring material, and there are many questions that have been asked about liquid screed for flooring, and especially in connection with underfloor heating systems. If you are considering flooring for a home or commercial project, then liquid screed is a highly versatile material. It also has a number of very important benefits when used in conjunction with underfloor heating, not the least of which is that it provides 100% thermal efficiency for the heating as the heat cannot get trapped in air pockets and the fact that the thermal conductivity is nearly double that of a standard traditional sand and cement screed.
At UK Screeds we supply and install liquid screeds throughout England and Wales, no matter the size of your project. As specialists in the installation of underfloor heating and liquid screeds, we can help with any project, and often at short notice. In this article, we will endeavour to address the most common questions that we get asked about our liquid floor screeds. As you might imagine, we are frequently asked to provide our liquid screed services in London, but the answers will apply anywhere.
Why use anhydrite liquid screed instead of sand and cement screed?
Our liquid anhydrite screeds use anhydrous (dry) calcium sulphate as a binder, which becomes gypsum when mixed with water. The screed goes by a number of different names including gypsum screed, calcium sulphate screed, self-levelling screed, flowing screed, and liquid screed, among others, but all refer to the same product. Anhydrite liquid screed has gained favour over sand and cement screed because of much faster installation and drying times, its’ many benefits when used in conjunction with underfloor heating, and the fact that it does not curl and has minimal shrinkage. It is also environmentally friendly, containing around one-third of recycled materials.
Is any preparation needed before laying a liquid screed?
Yes, most certainly there is. The liquid screed must only be laid on a suitably prepared substrate which must be clean and free of any objects such as dropped nails, or plaster. The screed can be laid bonded directly to the substrate, or it can be laid unbonded with the substrate covered in a suitable 500-gauge polythene tanking membrane. It can also be laid over underfloor heating pipes on top of a tanking membrane covering insulation boards of polypropylene, in which case it is known as a floating screed.
How long does it take to install a liquid screed?
Our liquid screed is delivered to the site premixed and is connected to a pump and a hose. The screed is then pumped into position, Our teams can lay as much as 2,000 square metres in a single day, which is around 20 times as fast as laying a sand and cement screed by hand.
How long is it before the screed is dry enough to walk on?
Our liquid anhydrite screed will be dry enough to walk on within 24 – 48 hours after installation which is perfect when you have other tradesmen who need to carry out work on the project as there is absolutely minimal delay, especially when you compare this with sand and cement screeds.
What are the benefits of liquid screed used with underfloor heating?
Because the screed is in liquid form, it will totally envelop the heating pipes so there are no gaps or voids which you get with sand and cement laid by hand. This makes for perfectly even transmission of heat into the room. The screed also has around twice the thermal conductivity of sand and cement so less energy is required to heat the room to the required temperature. Liquid screed can also be laid a lot thinner than sand and cement, typically requiring only a 30mm covering over and above the heating pipes, making 45mm in all, so this also helps with the speed of heating.
Liquid screed cannot be used in wet rooms, or anywhere else where there may be water ingress. As it dries, it also produces a fine layer of particles on the surface known as laitance, and we need to remove this by sanding 7 – 10 days after pouring the screed.
Those two points aside, there are so many advantages to using liquid screed over and above old school sand and cement, and this is why liquid anhydrite screeds have become so popular.