All About Installing Hardwood Flooring Over Radiant Heat

by Jeff Hosking – Hosking Hardwood Flooring
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Feel the heat!

With new building and remodeling practices, the demand for using in-floor radiant heat has increased dramatically with in the last 25 years. Radiant heat provides an even warmth with no cold spots within a room and provides a comfort that cannot be matched by any other type of heating system. Over the years, we have installed a lot of wood flooring over different types of radiant heat systems including many for the PBS television series "This Old House". See About Us.

Early in-floor radiant heat systems were temperamental, expensive and only a handfull of heating companies had the experience to install them. Nowadays, radiant heat systems have become a lot more prevalent, affordable and reliable. Using the wrong wood flooring, improper installation methods or lack of maintaining proper relative humidity levels with a radiant heat system can be devastating. Unlike conventional heating systems which emit heat from the base of walls or up through vents in the floor, radiant heat transfers the heat directly under and up through the wood flooring with temperatures of 80 degrees or higher. Due to the natural characteristics of wood, absorbing and holding ambient moisture, along with the ability of the wood floor boards to expand and contract with different moisture levels within its environment, the dry heat directly under the wood flooring can cause flooring to dry out quickly and contract in size, causing cupping and/or large open gaps between the boards. The surface temperature of the subfloor should not exceed 80 degrees.

In addition, not all species of wood are good candidates for an installation over radiant heating systems. We do not recommend using Maple, Pine, Hickory or Brazilian Cherry because they are noted to be unstable wood species. The thickness of the particular flooring being used can also make a difference as to how much heat is transferred to the surface. Radiant heat contractors usually adjust their systems to match the type and thickness of the flooring so that it will perform as it should. The surface temperature though, should not exceed 80 degrees.

What is the best wood flooring to use over radiant heat?

FLOATING ENGINEERED WOOD FLOORS

The best type of wood flooring construction to use would be a "Floating" Engineered Floor. For examples, look at our Northern Lights collection. One of the benefits of using a floating floor is that the floor boards are locked together at the joints of each board (not nailed, adhered or attached to the subfloor in any way). This allows the whole floor to move as a single unit if a dimensional change (expansion or contraction) within the wood floor takes place. In addition, an engineered floor with cross layers of plywood backing makes for a more stable floor with less chance of dimensional movement than a solid wood floor. Floating engineered wood flooring can be installed over most all subfloors and surfaces (except carpet) as long as they are flat and secure. Using a floating floor will drastically reduce any possible seam contraction (opening of joints) between the floorboards.

 There has been some concern from homeowners that floating floors will be more noisy when walked on compared to a nail down or glued down installation of flooring. We do not believe that to always be the case. For example, using a style that is 1/2" or thicker will be more sound deadening. There are also underlayment pads available that dramatically reduce sound transfer when walked on. Installing a floating floor is a very quick and easy installation for a "Do it Yourself-er." The boards are simply glued or (depending on style purchased) clicked together, thus eliminating the need of using nails or staples to secure the flooring to the wood subfloor - that may puncture the radiant heat tubing. There are many different styles and colors of floating wood floors to choose from.

DO MANUFACTURERS WARRANTY THEIR "FLOATING FLOORS" OVER RADIANT HEAT? Most manufacturers that manufacturer engineered floating floors provide a warranty for installations over radiant systems (with the possible exceptions of their Maple and Brazilian Cherry species), but the installation of their flooring have to be done according to their specifications. The surface temperature of the subfloor should not exceed 80 degrees. A floor that is too hot can become dried out and distorted. For more on Floating floors see our article All About Floating Floors

The Engineered Floating floors recommend using are:  Vintage Hardwood Flooring - Anderson Engineered Wood Flooring (specified styles) - Kahrs Wood Flooring - Somerset Engineered Flooring - WeCork Click Lock Flooring

NON-FLOATING ENGINEERED WOOD FLOORING

For more information about Engineered Flooring see our article All About Engineered Wood Floors.

Can 3/4" Solid Wood Flooring Be Used Over Radiant Heat Systems?

If a Solid 3/4" thick wood floor is desired , it is recommended to use "Quartersawn" flooring (not usually available factory prefinished). "Quartersawn" is a method of cutting the boards from the log, so that the direction of the grain of the wood are vertical instead of horizontal (plainsawn). Quartersawn flooring is more stable than the commonly used "Plainsawn" flooring because the expansion and contraction within quartersawn wood flooring is more vertical than across the width of the board. "White Oak" Quartersawn flooring is very stable and is recommended to use. Also, if a 3/4" thick solid wood floor is desired, using narrower boards is a better choice than using wider plank flooring because there are more seams to take up any movement within the floor. Since 3/4" thick flooring can only be nailed or stapled down, great care has to be taken to avoid puncturing the radiant heat tubing. The surface temperature of the subfloor should not exceed 80 degrees. A floor that is too hot can become dried out and distorted.

For more information on Solid Wood Flooring see our article All About Solid Wood Floors.

DO MANUFACTURERS' WARRANTIES COVER SOLID 3/4" THICK FLOORING INSTALLED OVER RADIANT HEAT? There are no warranty provisions for 3/4" solid hardwood flooring warranty over radiant heating systems. 3/4" thick solid hardwood is just too volatile and no manufacturer will guarantee against warping, splitting or cracking if their 3/4" solid is installed over radiant heat.

Can Laminate Flooring be used over in floor Radiant Heat Systems?

Using a laminate flooring (like QuickStep) is another option if you plan on installing over radiant heat. The top layer of laminate flooring is basically a photograph of the flooring style which is then laminated to a dense center core which creates excellent stability and structural integrity. It's important to keep in mind that the surface temperature of the subfloor should never exceed 80 degrees. A floor that is too hot can become dried out and distorted.

DO MANUFACTURERS' WARRANTIES FOR LAMINATE FLOORING COVER INSTALLATION OVER RADIANT HEAT? There are provisions in laminate flooring warranties for installation over radiant heat systems but one manufacturer's installation guidelines may be different from another's. Check with the particular manufacturer you're using and make sure that during the installation process you follow their requirements for installation over radiant heat. Failure to follow the manufacturer's installation instructions may void your warranty.

Laminate flooring recommended for use over radiant heating systems: Johnson High Performance Laminate Flooring - QuickStep Laminate Flooring - Mohawk Laminate Floors

For more information on Laminate Flooring see our article All About Laminate Flooring.

Can Luxury Vinyl Plank Flooring be used over in floor Radiant Heat Systems?

Vinyl is a great hard surface flooring type to install over Radiant Heating Systems. Much like laminate, the top wear layer offers a realistic visual of real wood flooring (or sometimes a tile visual). The durable core of vinyl makes it the perfect option for busy homes and there are so many options these days that there is something out there for everyone. Our favorite luxury vinyl planks are from: Johnson Luxury Vinyl Flooring - MSI Everlife Luxury Vinyl Flooring - Southwind Luxury Vinyl Floors - Earthwerks Luxury Vinyl Planks

IMPORTANT: Moisture Testing

TEST FOR MOISTURE IN CONCRETE SLABS: Newly poured concrete slabs can contain a lot of water and they should be allowed to cure for 60-90 days prior to having any type of flooring installed. All concrete slabs, old or new, should be tested for moisture levels prior to installing any type of flooring. An easy way to check for moisture is to tape the edges of 3 foot by 3 foot square pieces of 4-6 mil plastic sheet down in several different areas of the slab. Wait 48 hours before looking to see if any moisture (condensation) builds up under the sheets. If signs of moisture are present, then the moisture problem has to be corrected prior to installing any flooring.

Moisture levels within a slab either on grade or below grade can vary during different times of the year depending on the ground water (water table). Due to this and also depending on your particular environment you may have a problem later when using any direct glue down (non-floating) engineered floor. This is because the adhesive used to glue the engineered flooring down may allow this moisture transfer to enter the wood flooring. Additionally the flooring could become detached from the concrete slab.

Floating floors are in our opinion the best and safest type of flooring to use in these types of situations. Using a floating floor allows you to create a barrier between any possible moisture later by laying 4-6 mil plastic directly over the concrete which will act as a moisture retarder.

Remember: Even the best wood flooring will react to the presence of moisture. In the dry winter heating months, moisture leaves the wood causing the floor to contract, which can leave unsightly gaps between each plank. In the summer months when the humidity is higher the wood will absorb excess moisture and expand and the gaps will disappear. If there is too much moisture it may cause the wood planks to cup, or buckle. This is why it is important when installing a wood floor to acclimate the wood to the home from 4 to 7 days or more prior to installation and to leave the proper expansion gap around the perimeter and at all fixed objects. It is also important to keep the home's relative humidity level at between 30 - 50% or what the manufacturer recommends. Doing this will help minimize any movement within the wood flooring later.

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Before you purchase your flooring read our other articles:

All About Solid Wood Flooring
All About Engineered Wood Flooring
All About Floating Engineered Wood Floors
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