Lumber Liquidators recommends floating floors – flooring not attached to the subfloor – for radiant heat applications. To ensure performance, the consumer should be aware of risks associated with nailing or gluing solid wood over radiant heat and ensure product selection and installation practices are appropriate for the application. If you choose to use solid wood, select quarter-sawn or rift-sawn materials. Note that even using solid wood species with known positive dimensional stability* characteristics than others, cannot predictably be guaranteed to perform well in every application. In addition, radiant systems if not monitored and controlled properly can negatively impact the long term finish performance of wood flooring and may result in finish chipping, peeling or hazy finish.
Here are the recommended choices for in-floor heating:
Floating floors – Most recommended because these types of floorings are installed over an underlayment and not attached or fixed to the subfloor. The flooring is free to move as a total unit to better accommodate subfloor movement and environmental fluctuations (moisture and temperature).
Engineered flooring – Works well over radiant heat because its unique plywood construction creates greater stability as each wood layer is positioned perpendicular to the other thereby resisting movement from environmental fluctuations (Depending on the selection can be nailed, glued or floated over the subflooring). If choosing engineered flooring for a radiant heat application, the consumer is advised to select a product constructed using a relatively stable wood species on the top surface. Consult your local Lumber Liquidators store or customer care for assistance if needed.
Quarter-sawn or rift-sawn – This cut or style of solid wood flooring is most preferable because it tends to expand more upwards in the direction of the grain with less side to side movement common with plain-sawn cut flooring. In addition, quarter-sawn solid flooring reduces the likelihood of side gapping and board edge cupping due to environmental fluctuations.
Strip flooring; boards 3” wide and less – Selecting a flooring product in a width measuring 3” or less is a better choice than planks or wider flooring because narrow boards will allow more board movement and will expand and contract less under varying environmental conditions when compared to wider boards. As a general rule, wider boards can have wider side or seam gaps.
Because of the wide array of radiant heat systems on the market, each with its own features, please consult with your radiant heat provider for recommended installation methods. Newly installed systems should be operating some two weeks prior to wood flooring installations. This precaution helps to further dry out any unknown pockets of trapped moisture. Hydronic systems must include in-floor temperature sensors and an outdoor thermostat that allows the system to adjust the water temperature according to anticipated heat loss. Radiant heat contributes to the drying out of all woods.
Make sure the board moisture content is approximately 6-9% before and maintained well after installation. The use of a humidification system may be required to maintain the proper humidity level. The indoor relative humidity must be maintained between 30-50% year round. Failure to do so can result in edge cupping, squeaking, de-lamination, splintering, or face checking. During installation, reduce thermostat to 65°F. 48 hours after installation, slowly raise the temperature of the heating system to its preferred operating level over a period of 5 days. The surface temperature of the subfloor must never exceed 85°F in any location. Avoid shock to the floor, the temperature setting must always remain within 15°F of normal operating level, adjusted gradually and should never be turned completely off. Excessive heat, rapid heating, and/or failure to maintain humidity levels between 30% and 50% is likely to result in cracking, cupping, squeaking and other forms of floor issues. Small surface splits (checking), particularly at the ends of planks, should be expected with installations over radiant heat and does not constitute a product failure.
*Wood stability refers to predictable movement that can be expected in a given wood species after installation once in service. Note that even when using an ideal species for radiant applications actual wood performance can still vary due to the radiant system construction, it operation and installation techniques.