It is vital that your sub-floor is properly prepared before laying your underfloor heating system to ensure that the system operates correctly without any problems.
The actual preparation requirements will depend on exactly which system you are installing and you should read the instructions supplied with your system to confirm these. However, the main pointers are as follows:
Always ensure the base is suitably insulated. If you are unsure or if the base is not well insulated you should use thermal tilebacker board on the base to ensure your system will meet your expectations.
Always ensure the floor base is secure for your chosen floor covering. Particularly when installing tiles above underfloor heating you must ensure that the floor base is secure and if installing onto floorboards you should use thermal insulation boards or marine ply glued and screwed onto the floorboards to secure the surface.
Always ensure the floor base is clean before commencing laying your electric underfloor heating. All dust, debris and loose tiles etc. should be removed prior to installing your system. Additionally, if the floor base has any oil or tar based residue this should be removed or sealed before laying your underfloor heating.