When should I commission underfloor heating?

As per BS 5385-3, traditional sand and cement screeds should be at least 21 days old, at which point the underfloor heating can be increased by 5⁰C every day until the maximum water temperature advised by the underfloor heating manufacturer is reached; commissioning can begin much sooner with an ARDEX Screed, in as little as 3 days. The underfloor heating should then be turned off for approximately 24 hours to allow the screed to cool down to room temperature. If site conditions are cool, maintain the screed and room temperature at 15⁰C or just above by adjusting the heat input accordingly. It can then be tiled as normal using the appropriate ARDEX Cement-Based Tile Adhesive.