If you are installing underfloor heating in a new building it needs to be covered with a floor screed. For many years now a floor screed has been made up using just sand and cement, often mixed on site in a cement mixer, and then laid by hand by a worker using a hand trowel to level it out.

However, in the last few years there has been a large change over to using liquid screeds in place of sand and cement because of the many benefits that they have.

One advantage is the speed of laying, because when carrying out floor preparation in Hungerford, at UK Screeds, we simply attach a pump and hose to the delivery truck (the screed is delivered ready mixed) and then pump it on to the substrate. This can be up to 20 times as fast as laying sand and cement by hand.

But the benefits don’t stop there by any means. Our anhydrite screeds, as they are called, don’t curl as they dry, and any shrinkage is absolutely minimal. They need far fewer expansion joints – just across some doorway thresholds. This makes them fully compatible with large stone tiles which can be vulnerable to cracking should the screed beneath them shrink.

Fully Enveloping The Heating Pipes

Another big benefit when installing underfloor heating is that the screed will fully envelop the heating pipes. When you use a sand and cement screed it is very difficult indeed to achieve this, and that means that there are bound to be gaps and voids which will mean that the heat transfer into the room is not perfectly even, as it is with our liquid screeds.

Not only that, but our liquid screeds can be laid a lot thinner than sand and cement. This means that you don’t need as much material, and in turn it follows that the underfloor heating will heat the screed, and therefore the room, more quickly, thus using less energy, which results in lower energy bills. In addition to that, the thermal conductivity of liquid screed is almost twice that of sand and cement, again resulting in faster warm up time and requiring less energy, and also providing greater controllability.

When installing underfloor heating this will usually be over insulation boards, and these need to be flat on the floor, so if there is any piping running over the substrate it is necessary to cut grooves in the boards in order to accommodate them. On top of this is laid a layer of 500-gauge polythene sheeting which needs to be lapped up the walls at right angles and taped or glued into place. This is necessary to stop the liquid screed from escaping.

The heating pipes then need to be screwed or stapled into place on top of the membrane (not underneath it) with fixings every 300mm as a minimum and more fixings on the bends. The fixings pierce the membrane and seal the holes themselves so there will not be any leaks.

Finally, before pouring the liquid screed into position, the heating pipes must be filled with water in order to help keep them in place.