Radiant heat under ceramic tile or stone

Questions and concerns are often raised when ceramic tile or stone is to be installed over a radiant-heating system. These concerns usually are regarding any detrimental effect that the heat from the radiant heating might have on the bond of the tile, approved substrates and when the system can be activated. Typically, the maximum heat from a radiant-heating system does not exceed 85°F (29°C); this level of heat would not affect installation systems and accessories that are designed for tile and stone.

The TCNA Handbook for Ceramic, Glass, and Stone Installations provides recommended minimum cure/dry times for individual substrates and products. Minimum cure times are not listed here due to the many combinations of systems in the TCNA Handbook; refer to the TCNA Handbook for specifics. At a brief glance, these individual substrates and products entail:

Substrate suitability

• Wood or Concrete

Adhesive suitability

• Cementitious or Organic

Underlayments

• Gypsum or Cementitious

Type of system

• Electric
• Hydronic (water)

The handbook further recommends the following installation practices. Always follow manufacturer’s recommendations when installing product:

Substrate suitability

• Wood: Over structurally sound wood floors that are subject to residential traffic
• Concrete: Properly cured, on slab-on-grade, no bending or stresses, no moisture intrusion, interior dry areas, limited wet areas with waterproof membrane (ANSI A118.10)

Adhesive suitability

• Cementitious: Latex-Portland cement meeting ANSI A118.4 and ANSI A118.11. ANSI A118.1 (limited to TCNA RH135-09, over backer board)
• Organic: No TCNA recommendations for use with radiant-heating systems

Underlayments

• Gypsum: Minimum thickness is 3/4" (19 mm) above floor-warming systems. Properly primed, may require plastic lath.
  • Performance: ASTM C627 Standard test method for evaluating ceramic floor-tile installation systems using the Robinson-type floor tester
  • Compressive: ASTM C472 Standard test methods for physical testing of gypsum, gypsum plasters and gypsum concrete
• Cementitious, Self-Leveling: Minimum thickness is 1/2" (12 mm) above floor-warming systems. Properly primed, may require plastic lath.
  • Performance: ASTM C627 Standard test method for evaluating ceramic floor-tile installation systems using the Robinson-type floor tester

Floor-warming systems

• Electric:
  • Mat Design: One or a combination of standard mat sizes that can be used to provide floor heating for the entire room
  • Cable Design: Allows contractors to manually adapt the floor-heating covering on site for any room, including those with curves and angles
• Hydronic (water): Hydronic radiant floor-heating systems use a boiler to heat up hot water and a pump to circulate the hot water in plastic pipes. The pipes, embedded in the floor, carry heated water that conducts warmth to the surface of the floor where it radiates heat up into your room.

MAPEI has a full line of electric radiant-heating systems that are suitable for use under a variety of floor coverings. Whether you are looking to take the chill off a bathroom floor or heat an entire room, MAPEI’s Mapeheat has the solution you need.

Mapeheat Mat: Pre-wired floor-heating fabric; compact 1/8" (3 mm) profile for minimal floor buildup; even heat distribution, with no cold spots; easy installation; standard and custom mats available

Mapeheat Cable: Suitable for wet environments, such as showers and steam rooms; for use with Mapeheat Membrane or Mapeheat Cable Guides

Mapeheat Membrane: Crack-isolation and waterproofing membrane; thin profile of less than 1/4" (6 mm); replaces plywood or cement board as tile underlayment