n my own career in the plumbing and heating industry, which spans 26 years, I have seen many improvements, the most significant of which I believe is the advent of flowing gypsum screeds. These liquid screeds are superior in many ways to sand and cement, but most notably, they can be force dried quickly and safely; provided the right equipment is used and best practice is observed. Flowing gypsum screeds do not curl; they need no reinforcement, shrinkage is extremely low and large bays can be laid without risk of cracking.
The drying times given on screed datasheets are generally based on a fixed environment, at 20ºC and 60% relative humidity throughout the stated drying period. It is rarely if ever possible to achieve these conditions naturally on a construction site in the UK. Typically, an anhydrite screed, installed at 50mm depth, will be said to have a drying time of 60 days, given these fixed environment conditions, but on a construction site, this will often extend a total of 90 days or sometimes even longer.
A brief history – recognising the full potential
However, I recognised the potential of force drying some years ago, and developed unique technology specifically for use with liquid screed flooring, before launching the ForceDry business in 2013. Using this specialist technology, combined with strict environmental control and following the screed manufacturer’s instructions, can bring both the total drying and commissioning time down to just 28 days.
Time is money in construction, so being able to shave up to around 70 days off installation time for liquid screed floors by force drying represents a very significant cost saving for contractors and developers alike, and brings welcome certainty to any construction programme.
We have worked on many housing developments over the years, and I have often been struck by the fact that developers often specify radiators for the affordable housing element of the project, keeping underfloor heating for the more expensive properties. There seems to be a general perception that underfloor heating is a ‘high-end’ item, but I know from experience that underfloor heating systems with liquid gypsum screeds are quick and economic to install. I was convinced underfloor heating could be a viable solution for all types of property – including affordable housing.
So, we decided to undertake a study to compare the costs of a radiator-based heating system with an underfloor heating system. We worked with some of the UK’s leading contractors, giving them a brief to install three different specifications: traditional radiators with a 75mm sand and cement screed, traditional radiators with a 50mm flowing screed and a 50mm flowing screed with underfloor heating. The brief was based on installing the systems in a one-, two- and three-bedroom property. We then analysed the costings and data to produce our findings.
The results showed that for an 80m² dwelling, installation costs for the radiators with a sand and cement approach ranged from £3003.72 to £3483.10; for a 50mm flowing screed with radiators, costs started at £3163.72 to £3563.10 and for a 50mm flowing screed with underfloor heating, costs ranged from £3464.63 and £4082.30. The costs for the underfloor heating approach also included force drying.
This study shows that the underfloor heating method is only marginally more expensive to install than radiators. However, when site running costs and penalty clauses for development overruns (which can run into hundreds of thousands of pounds) are also taken into consideration, the significant, additional cost savings are clear.
But there is an additional, major benefit in using liquid gypsum screed flooring – it is kinder to the planet than sand and cement screeds. Liquid gypsum screed comprises 98% recycled waste material, requires less energy to produce and, because it is thinner, uses less material. As a result, a 50mm gypsum screed contains 20kg less embedded carbon per square metre than a 75mm sand and cement equivalent. In addition, liquid gypsum screed floors have excellent conductive properties so are highly efficient and economical when used with underfloor heating.
So there is no reason why developers should not specify underfloor heating for social or affordable housing. Using liquid gypsum screed flooring with force drying, combined with underfloor heating, is a viable solution. This approach is economical to install, environmentally-friendly and performs very efficiently. It can save developers and property owners time and money during the build and allows them to offer a superior product specification. Furthermore, homeowners and tenants benefit from the comfort, economy and low maintenance this kind of system offers.