Installation Guide

32 CONCRETE SUBFLOORS
Discussion on Schluter
®
-DITRA-HEAT installations over
concrete subfloors
CONCRETE SUBFLOORS
Elevated Concrete
Elevated concrete substrates, as found in multi-story residential construction, hotels, etc. will typically be located over another occupied
space that is at or near room temperature. For these applications, the DITRA-HEAT-DUO membrane with integrated thermal break is an
excellent means to reduce the warm up time and will typically produce satisfactory results.
Concrete on or Below Grade
Concrete substrates placed on or below grade, as in basements or first floors of single-family dwellings, have the potential to absorb even
more heat energy than elevated concrete substrates and further extend the warm up time. This effect is exacerbated if there is no insulation
provided below the concrete on ground.
If the concrete on grade is sufficiently insulated, the DITRA-HEAT-DUO membrane with integrated thermal break can reduce the warm
up time and satisfactory results will typically be achieved. If the concrete is not insulated, the DITRA-HEAT-DUO thermal break is likely
not sufficient to reduce the warm up time to a satisfactory value. In fact, it is possible that the heat loss to the concrete is such that the
tile covering will not reach the desired temperature. For these applications, it is likely that providing insulation on top of the concrete will
be required to produce satisfactory floor warming performance. If providing insulation on top of the concrete is not possible, the use of
the continuously alternating 3-2 stud heating cable spacing is recommended. This alternating cable spacing will provide a 20% increase
in heat output compared to the 3 stud spacing and a similar reduction in warm up time, over and above the reduction obtained with the
DITRA-HEAT-DUO membrane, depending on your particular application or installation. Please contact a design professional (e.g., HVAC
contractor, engineer or architect) and Schluter Systems to discuss such projects during the planning stage.
Concrete substrates absorb more heat energy than wood substrates. As such, the time required for an electric floor warming system, such
as Schluter
®
-DITRA-HEAT, to bring a tile covering to the desired temperature will be longer for applications over concrete than for applications
over plywood/OSB. The warm up time will vary depending on many factors, including concrete thickness, temperature, location, and
insulation. Therefore Schluter Systems cannot predict or guarantee the temperature increase over time as follows: