How to Install Hardwood Floors Over Radiant Heat
With advances in heating and insulation technology, and effective management
of wood's natural expansion and contraction, builders, architects and
designers achieve faultless installations of hardwood flooring over
Parquet floors are readily used in radiant heat applications. With
strip flooring, the wider the board, the greater the potential for gaps
between the boards when they contract with seasonal changes in temperature
and humidity. Tongue-and-groove strips are recommended and beveled-edge
boards show fewer seasonal gaps.
It isn't recommended to use radiant floor heating under plank flooring
wider than 3". Despite all your precautions, there is a high probability
the user will not be satisfied.
How It Works
Radiant heat systems use a three-stage process to convey heated water
to its destination.
- A water heating system that can be either a standard boiler, water
heater, a geothermal heat pump or even solar panels.
- The heated water is pumped through a tubing network installed in
- As the warm water moves through the tubing network, it releases
its energy and returns to the boiler system to be reheated.
Good communication with the radiant heat system designer is critical.
Everyone should be notified of any work pertaining to the installation,
especially if specifications are changed.
To ensure a superior end product, pay attention to the following factors
before, during and after installation:
Work with the system designer to choose the subfloor option (see illustrations.)
The heat system designer is responsible for the subfloor installation,
but you will want to be familiar with the choices. Direct contact of
the tubing with the flooring is not recommended. The subfloors shown
here are recommended for hardwood floor installations.
Plywood (5/8") or oriented strand board (3/4") make good candidates
for subfloor materials in radiant installations. Particleboard subfloors
are not recommended by radiant heat companies.
Provide the radiant heat system designer with the hardwood flooring
dimensions, species, and the desired temperature of each room. This
will give him/her the information needed to calculate the necessary
Consult with the system designer to determine the tube network layout,
so you'll know where the tubes are before you nail down the floor. It
is best to have the tubing spaced evenly down the joist cavity (between
the sleepers). Then you can nail down the finished flooring onto the
sleepers on eight-inch centers. When the tubing circuits are crossed
over the center of the joist cavity, have the system designer use nail
plates to protect the radiant circuits from being punctured.
The following climate controls will minimize expansion and contraction
during and after installation of the floor.
Mechanical Humidity Control: The heating/ventilation/air conditioning
(HVAC) system should have mechanical humidity control. This will monitor
the room and keep the relative humidity at an even level, which will
keep the equilibrium moisture content of the floor stable.
Heat Transfer Point Control: The system designer also should install
a set point control that will monitor the wood floor temperature. The
set point control should either reduce the system water temperature
or temporarily cycle the system off to prevent overheating the flooring
if equipment malfunctions.
Exterior Thermostat: An exterior thermostat is recommended to protect
the perimeter of the system from condensation absorption during the
spring and fall when rapid temperature changes may occur.
Once the subfloor, tubing and climate controls have been installed,
the heating system should run for at least 72 hours to bring the house
to the desired relative humidity.
Temporary, unvented sources of heat - such as propane-fired "salamanders"
- can add excessive amounts of water vapor. Avoid them if possible,
but if they must be used, leave windows open to vent the humidity.
Now follow the customary procedures for installing any hardwood floor.