The Complete Guide to Screed Over Underfloor Heating

Underfloor heating is now standard specification in most new residential and commercial builds across the UK. Choosing the right screed to go over your UFH system is one of the most important decisions on any project — get it right and the system performs brilliantly for decades. Get it wrong and you face cracked screed, poor heat distribution, and expensive remediation.

Why Liquid Screed Is the Industry Choice for UFH

Liquid anhydrite screed is the preferred choice for underfloor heating for three reasons. First, it flows around and under the pipes, eliminating air voids that act as insulation and reduce heat output. Second, its thermal conductivity is higher than sand and cement, so heat transfers to the floor surface more quickly and efficiently. Third, it can be laid at just 25mm above the pipe — compared to 65–75mm for sand and cement floating screed — which means faster warm-up times and a lower floor build-up.

The UFH Commissioning Process

Before any floor finish is laid over a UFH system, the heating must be commissioned. This is mandatory for anhydrite screeds and best practice for all screed types. The process involves gradually raising the water temperature over several days to drive residual moisture from the screed. Start 28 days after installation: run at 25°C for 3 days, increase by 5°C per day to maximum operating temperature, hold for 4 days, reduce. Once moisture content is below 75% RH (0.5% CM for anhydrite), floor finishes can be laid.

Compatible Floor Finishes Over UFH Screed

Not all floor finishes are suitable over underfloor heating. The best performers are: porcelain and ceramic tiles (excellent heat transfer, no expansion issues), stone (excellent but ensure the screed is fully dry and stable), LVT and vinyl (good, but check manufacturer UFH temperature limits), and engineered timber (suitable up to certain temperatures — check manufacturer guidance). Solid hardwood is generally not recommended over UFH due to movement. Carpet over UFH is inefficient and should be specified at minimum tog rating.

screeding.com installs liquid screed over UFH systems nationwide. Get a free site survey and instant quote — we work directly with your UFH installer to confirm the correct specification before a single bag of screed is mixed.