Is there any special adhesive I need to use to tile over Fastwarm® boards?
Yes, for cement and wooden sub-floors a rapid-setting flexible tile adhesive will be required. The special polymers added to flexible adhesives will make allowances for any tile floor movements caused through heat expansion and contraction by the underfloor heating: the added polymers will also accommodate any slight flexing in a wooden sub-floor; don’t forget, a flexible tile grout will also be required.
