There is nothing new about underfloor heating. It was most certainly in use in Roman times, and there is some argument that it can be traced back a lot farther than that. The Romans didn’t have the benefit of the heating systems that we have today, but they had voids cut into the floor of homes and heated the air using strategically placed fires.
Obviously, a lot has changed over the last 2,000 years, and there have been some major developments resulting in the systems that we have available now. Underfloor heating in recent years was confined to higher-end homes but today is becoming specified more even for affordable housing. In fact, a recent study showed that there was not a lot of difference in the overall cost between radiator systems and underfloor heating, and indeed the cost of underfloor heating systems has been reduced even further by the use of the liquid screeds that have been developed in recent years. The overall cost of installing and commissioning underfloor heating has been reduced by the use of these liquid screeds in combination with force drying.
There are several benefits to using liquid screeds in conjunction with underfloor heating, one of which is that laying the screed is just so much faster than laying a traditional one. In any building contract, time is money. Laying a traditional sand and cement screed is done by a labourer on hands and knees trowelling the screed as flat and level as he can. This is an extremely laborious job. However, our liquid screeds that we install at UK Screeds are poured into position using a pump and a hose. Compared with hand installation, this is calculated to be around 20 times as fast, so it saves a huge amount of man hours.
Furthermore, a liquid screed can be installed using less material than sand. This compares with at least 75 mm for sand and cement. Liquid screed does cost more than sand and cement but taking into account the fact that less material is used and combined with the speed of laying, there is not a lot of difference.
On top of that, a liquid screed can be force dried because it doesn’t curl, as can happen with sand and cement. You need to use the right equipment, but this can reduce drying times before the final flooring can be laid by a considerable amount. A typical anhydrite screed installed to a depth of 50 mm is said to have a drying time of 60 days. However, this assumes that there is a steady temperature of 20°C and 60% relative humidity for the whole drying period which, in the weather we have in the UK, is not all that likely. That means that drying times can be quite a bit longer.
However, using specialist force drying equipment and controlling the temperature and humidity of the environment can bring the total drying time of a liquid anhydrite screed down to just four weeks. Furthermore, the underfloor heating can be switched on to minimum after 7 days or so and this can be turned up by 5°C each day to a maximum of 55°C which can be left on for a week before being gradually reduced again. The combination of these techniques can bring the overall drying time down considerably.
There is one thing which liquid screeds require which others don’t, and that is sanding. During the first few days after laying, liquid anhydrite screed produce a layer of laitance on the surface as it dries, which are tiny particles of dust, and this layer must be removed before the final flooring is attached because it will otherwise compromise the final flooring finish.
At UK Screeds, we use floor sanding machines in Dorset and elsewhere to remove the laitance between 7 and 10 days after we have poured the screed. This will result in the surface of the screed being in perfect condition in order to accept the final flooring, whether that is wood, vinyl, tile, stone, or anything else.