When you are working on any sort of construction project, time is money, and the problem is that there can be so many things which can go wrong, causing delays on site. One of these concerns the drying times of screeds used to level out the floor surface, and in the case of underfloor heating being installed, cover up the heating system whether it is water-based or electric.
Once upon a time it was thought that underfloor heating was expensive, and only for a high-end property, but today it is actually economical to install it in any new build project if you use it in conjunction with the latest liquid gypsum screeds. A recent study compared the cost of installing a radiator system with an underfloor heating system using liquid screed and found that if you combine the underfloor heating system with force drying, there is virtually no difference in the cost, so it can be used in affordable homes as well.
On top of that, underfloor heating is very economical to run if you use a water-based system. True, electricity is expensive, but comparing the cost of a water-based system with a radiator system shows there is not much difference.
Certainly, installing a water-based system is more expensive than an electric underfloor heating system, but once you have covered the initial expense, the savings go on forever.
Using a liquid screed in Bristol with a water-based underfloor heating system has several advantages over and above the traditional sand and cement screed. When you install the screed, you need it to fully envelop the heating pipes, otherwise there will be voids which can have an effect on the transfer of heat into the room. Sand and cement screed is trowelled on by hand and it is almost impossible to ensure that the heating pipes are full covered.
On the other hand, a liquid screed is pumped into position using a hose and pump. And being liquid, it flows all around the heating pipes leaving no gaps. This means that the heat transfer into the room will be absolutely even, which is what you want.
Now a liquid screed will dry, once poured, to a point where it can be walked on within 24 – 48 hours, so that other contractors are not unduly delayed when working on site. However, the final flooring cannot be laid until the screed has fully dried.
Drying Times Are Quoted On Fixed Temperature And Humidity
The drying times that are quoted on screed datasheets are typically based on a fixed temperature of 20°C and 60% relative humidity. Unfortunately, getting a steady temperature and relative humidity throughout the stated drying time is very unlikely in the British climate. A liquid screed laid at a depth of 45mm to cover the heating pipes by 30mm is usually quoted as having a drying time of 50 days, but in the British climate that can often extend to 90 days or more.
However, if you combine a liquid screed with force drying, using the right equipment, the overall drying time can be brought down to around 28 days. That is a big time saving on any contract. Liquid screeds can be force dried because, unlike sand and cement screeds, they do not curl and they need no reinforcement. On top of that, shrinkage is extremely low, and large bays can be laid without a risk of cracking.
Another advantage of liquid screeds is that they can be laid more thinly than sand and cement, at 45mm instead of at least 75 mm. On a multi-floor building project this can save a considerable amount of height which is always a benefit. It also means that there is a weight saving as well. But, of course, in addition, it makes the drying time quicker.
The fact is that once it becomes obvious that the screed manufacturer’s quoted drying times are not a reality in the climate we have, force drying becomes an obvious answer. The trick is to use the right force drying equipment and control the environment – both temperature and humidity – and carry out appropriate moisture testing. Get all these right, and you can shave as much as two months off the installation and commissioning time for underfloor heating using a liquid screed, which has to be a benefit on any project.
