All About Installing Hardwood Flooring Over Radiant Heat
By Jeff Hosking, President of Hosking Hardwood Flooring
© 1997-2006, Copyright Hosking Hardwood Flooring. All Rights Reserved.
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 hand full 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 or installation methods over 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 85 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.
Photos courtesy of The Hardwood Council © 1999
There are several ways radiant heat systems can be installed.
This is the most common installation in home renovation.By installing the radiant heat tubing directly under the wood subfloor from below.
By installing the radiant heat tubing within a plywood underlayment system, directly over the existing concrete slab or existing wood subfloor.
By installing the radiant heat tubing within the concrete slab during the pouring of the concrete.
Any type of wood flooring used must be brought into the area in which it will be installed and allowed to acclimate for at least two weeks prior to the flooring being installed. We recommend the radiant heat be run at a temperature of 65-70 degrees two weeks prior to the wood flooring being brought in and until the wood flooring has been installed. Most newer radiant heat systems have exterior thermostats which will gradually bring up the temperature within the floor during the start of the colder season so that the heat will not shock the wood flooring causing the flooring to distort.
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 Mannington Engineered Flooring collections. 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 IN. 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 85 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 : Owens Plank Flooring - Harris Engineered flooring - Baltic Wood Floors - Anderson Engineered Wood Flooring (specified styles), Kahrs Wood Flooring,
(NON - FLOATING) ENGINEERED WOOD FLOORING
(Non-Floating) Engineered Flooring can also be used. Again, because of the stable plywood backing an engineered floor makes for a more suitable floor with less chance of dimensional movement than a solid wood floor. Most engineered flooring can be direct glued, stapled or nailed down, but care has to be taken to avoid stapling or nailing the flooring down and puncturing any radiant heat tubing. I DO NOT RECOMMEND GLUING DOWN ANY FLOORING DIRECTLY TO THE EXPOSED RADIANT HEAT PIPING. Doing so may cause damage to the radiant heat tubes and be a big expense if the heating system has to be repaired. I ALSO DO NOT RECOMMEND DIRECT GLUING DOWN ANY WOOD FLOORING OVER A BRITTLE LIGHT WEIGHT CONCRETE. If direct gluing down an engineered wood floor is desired and the wood sub-floor has a radiant heat panel system (shown above) with exposed tubing, I would recommend installing a 3/8 inch underlayment plywood over the piping first. Always follow the manufacturers recommendations as to the installation of their 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 inch 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 IN. 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 IN. 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 85 degrees. A floor that is too hot can become dried out and distorted.
For more information on Solid Wood Flooring - All About Solid Wood Floors
DO MANUFACTURERS' WARRANTIES COVER SOLID 3/4 IN. THICK FLOORING INSTALLED OVER RADIANT HEAT? There are no warranty provisions for 3/4 IN. solid hardwood flooring warranty over radiant heating systems. 3/4 IN. thick solid hardwood is just too volatile and no manufacturer will guarantee against warping, splitting or cracking if their 3/4 IN. solid is installed over radiant heat.
Can Laminate Flooring be used over in floor Radiant Heat Systems?
Using a laminate flooring (like Pergo or 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 85 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: Alloc - Armstrong - Bruce - Quick Step - Shaw - Tarkett
For more information on Laminate Flooring - All About Laminate Flooring
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.
Frequently asked questions about
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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Web Page: Hardwood Flooring Over Radiant Heat
by Jeff Hosking
Overall Rating: 4.4 stars -
By: Judy T.
February 26, 2014
Excellent article. This site has the best info re: manufactured flooring and installing over radiant in-floor heat. Weve been looking for this info for along time and finally found it!
By: wayne deswert
October 3, 2013
Very interesting and most helpful as we are building a new home and our builder is recommending radient heating
November 6, 2012
What is the ideal tempt. for supplying hot water through radiant pex tubing under quarter sawn wood?
By: susan o
September 25, 2012
It would be helpful to have some sort of cost estimate.
September 24, 2012
Good article with good advice thank you.
September 10, 2012
Thank you for making this clear in your article. We were almost going to purchase wide solid maple floors good thing we read this.