Best Practices Guide to Installing Wood Floors over Radiant Heating
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Installing wood flooring over radiant heat, guide
Specifications for Installing Radiant Heated Wood Floors over Slab-on Grade
Questions & answers abou thow to install wood floors over radiant heating systems

This article explains the recommended details for installing wood flooring over a radiant heated floor system.

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Detailed Guide to Installing Wood Floors over Radiant Heating

This article series discusses and provides a best construction practices guide to the selection and installation of building interior surface materials, carpeting, doors, drywall, trim, flooring, lighting, plaster, materials, finishes, and sound control materials. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

Readers should be sure to see RADIANT HEAT Floor Mistakes to Avoid. Also see INTERIORS of buildings, our home page for information about all topics relating to building interiors.

See these articles on radiant heated floors

FLOOR, WOOD RADIANT HEAT - guide to installing wood floors over radiant heat systems - this article is provided just below
RADIANT HEAT - usage guide, strategies for using radiant heat
RADIANT HEAT TEMPERATURES - at the boiler, in tubing, under floors, floor surface, thermostat & control settings
RADIANT SLAB FLOORING CHOICES - wood vs ceramic tile over a radiant heated floor
RADIANT SLAB TUBING & FLUID CHOICES - tubing and fluid choices for radiant heating
RADIANT HEAT Floor Mistakes to Avoid - proper and improper radiant tubing depth in slabs & slab insulation needs - what can go very wrong when the building contractor substitutes brawn for brains
SLAB INSULATION, PASSIVE SOLAR - slab insulation & vapor barrier placement in heated floor slabs
WOOD FLOOR DAMAGE - from radiant tubing run too hot

how to Install a Wood Floor Over Radiant Heating Systems: slabs, subfloors, etc.:

As described in the book, Best Practices Guide to Residential Construction Chapter 5, Interior Finish:

Radiant heating is a challenging application for wood floors due to the high temperatures, excessive drying, and greater temperature cycling to which the wood and finish are subjected.

Careful monitoring and control of the moisture levels of the flooring and structure at the time of installation are critical for success. Also, because a 3/4-inch wood floor over 3/4-inch plywood has an R-value of almost 2, similar to plush carpeting, wood systems generally must run at higher water temperatures than tile or vinyl floors. Large area rugs make it more difficult for the heating engineer to design a system that will heat the room without overheating the flooring.

Wood flooring can be installed over radiant slabs, or over dry systems where the hydronic tubes are stapled directly to the subflooring (staple-up) or laid on top in grooved panels.

Dry systems are more common in retrofits and generally require water 10°F to 20°F higher than thin slabs, leading to reduced efficiency, and often ruling out low-temperature heat sources like heat pumps or solar. Also, with less thermal mass than slab-based systems, dry systems are more prone to temperature fluctuations.

All radiant floor heating systems are designed to heat floors to about 80°F. Floors heated above 85°F are uncomfortable for occupants and may be damaged from the heat.

With any approach, the radiant slab or subfloor must be dry prior to installation. With slab systems, run the heating system for at least a week, up to three weeks if necessary, to dry the slab to a moisture content of 8 to 12% before installing the subfloor.

The subfloor and hardwood floor should be acclimated to the average annual moisture levels for the region and be within 2 percentage points of each other (see “Acclimatization,” page 167). Flooring that is installed too wet can lead to shrinkage cracks; flooring installed too dry can lead to expansion problems or cupping in humid summer weather.

To steer clear of problems, also follow these recommendations:

If possible, choose an engineered wood product rather than solid wood. Floating floors are best, since they are designed to accommodate movement.
If solid wood is used, avoid flooring wider than 3 inches—the narrower the better. If possible, use quartersawn wood, which swells and shrinks 30%–50% less than flat-sawn.
Choose a prefinished flooring coated on all faces. Prefinished flooring with chamfered edges (microbevels) will help conceal shrinkage cracks.
Increase nailing of strip flooring to 4 to 5 inches on-center.
If finishing on site, use a recommended sealer to reduce the chance of edge-bonding when the flooring shrinks, leaving large gaps every several courses.
Always use a vapor barrier under the flooring, but do not use asphalt-impregnated felt, which will give off fumes.
Avoid glue-down flooring. If used, make sure both the flooring and adhesive manufacturers approve the application.

Specifications for Installing Radiant Heated Wood Floors over Slab-on Grade

Over traditional concrete radiant slabs at least 4 inches deep, use either a floating hardwood floor or install subflooring and nail on 3/4-inch strip flooring. The subflooring can consist of two layers of 1/2-inch plywood floating over the slab (see “Installing Over Concrete,” page 168), or a single-layer 3/4-inch subfloor nailed to the slab with powder-actuated fasteners. Because it is thicker, the floating subfloor (Figure 5-15) will take slightly longer to heat up, but it does not risk puncturing the hydronic tubing.

Specifications for Installing Radiant Heated Wood Floors over Thin Slabs

In wood-frame construction, use a minimum 1 1/2-inch-thick slab of Gyp-Crete® or lightweight concrete, which provides thermal mass for the radiant floor. Above the slab use a floating hardwood floor, or nail strip flooring to 3/4-inch sheathing installed over the lightweight concrete.

Fasten the sheathing to 2x4 sleepers placed 12 inches on-center, with the lightweight concrete and tubing in between (see Figure 5-15 shown above). A two-layer floating subfloor, as described above, is also an option for larger rooms where the subfloor will be heavy enough to stay solidly in place without nails.

Specifications for Installing Radiant Heated Wood Floors over Staple-up and Panel Radiant Floor eat Systems

There are a variety of dry radiant systems that install just under or over the subflooring, making them ideal for retrofits. The tubing is either stapled to the underside of the subflooring, laid over the joists (with spacers to fur up the sheathing), or placed over the subflooring in grooved plywood panels.

Engineered wood floating floors are best with these systems, but nail-on hardwood flooring can work if installed with care.

-- Adapted with permission from Best Practices Guide to Residential Construction.

Resources: Manufacturers, Industry Associations, & Sources of Indoor Wall Materials, Flooring, Carpeting, Lighting, Sound Control Materials

Drywall Trims and Accessories

Clinch-On Products, A Deitrich Metal Framing Company www.dietrichindustries.com Nail-on and clinch-on galvanized metal corner beads

Con-Form International/Strait Flex www.straitflex.com Strait-Flex fiber-composite mud-on corner bead for inside and outside off-90 degree angles

Drywall Systems International www.no-coat.com No-Coat prefinished drywall tapes for inside and outside corners, off angles and bullnose trims

Flex-Ability Concepts www.flexc.com Curved metal top and bottom plates for curved wood or metal stud walls

Grabber Construction Products www.grabberman.com Drywall screws, corner clips, and fiberglass mesh tapes

Insta Arch Corp. www.instaarch.com Galvanized steel preformed and custom arches for drywall

National Gypsum Co. www.nationalgypsum.com ProForm tapes and finishing compounds

Pla-Cor www.pla-cor.com ABS corner trims, bullnose, 3-way corner caps, and flexible arches

Phillips Manufacturing Co. www.phillipsmfg.com Metal and vinyl corner beads, bullnose trim, and flexible bullnose and angled arch trim

Trim-Tex www.trim-tex.com Vinyl drywall beads, flexible arch beads, and finishing accessories

U.S. Gypsum Beadex and Sheetrock-brand tape-on metal corner beads and trims. Complete line of drywall finishing compounds

Vinyl Corp., A Deitrich Metal Framing Company www.vinylcorp.com Full line of vinyl beads and trim

Prefinished Wood Flooring

Alloc Inc. www.alloc.com Snap-together, no-glue long-strip and single-strip laminated flooring

Anderson Hardwood Floors www.andersonfloors.com Laminated strip, nail, glue, and floating

Armstrong World Industries www.armstrong.com Bruce, Hartco, and Robbins prefinished plank and engineered strip

BHK of America www.bhkuniclic.com Snap-together, no-glue laminated wood flooring

Columbia Wood Flooring www.columbiaflooring.com Prefinished solid strip

Duro-Design www.duro-design.com Floating click-lock oak flooring

Gammapar www.gammapar.com Engineered wood strip with oil, UV-cured urethane, or acrylic-impregnated finish

Junkers Hardwood www.junkershardwood.com Floating solid strip with metal clip installation

Kahrs www.kahrs.com Laminated strip with UV-cured acrylic urethane, nail, glue, or floating

Lauzon www.lauzonltd.com Prefinished strip, laminated strip, and click-lock laminated plank

Mannington Mills www.mannington.com Laminated strip and plank with polyurethane and aluminum-oxide finish

Medallion Hardwood Flooring www.medallionhardwood.com Prefinished solid hardwood strip and plank with aluminum-oxide finish

Tarkett Wood Floors www.harris-tarkett.com Prefinished solid hardwood, laminated, and long-strip flooring

MercierWood Flooring www.mercierdurable.com Prefinished solid strip and laminated strip with aluminum-oxide finish

PermaGrain Hardwood Flooring www.permagrain.com Acrylic-impregnated laminated strip and plank

Zickgraf Hardwood Flooring www.zickgraf.com Prefinished solid strip with UV-cured urethane with diamond and aluminum oxide

Bamboo Flooring Producers & Sources

Bamtex (a division of Wood Flooring International) www.bamtex.com Laminated bamboo and palm flooring

Duro-Design www.duro-design.com Laminated bamboo flooring with durable water-based finish

Gammapar www.gammapar.com Acrylic-impregnated bamboo flooring

Hawa Bamboo Flooring www.hawabamboo.com Prefinished bamboo flooring with aluminum-oxide finish

Natural Cork www.naturalcork.com Prefinished glue-down or nail-down 3-ply bamboo planks with aluminum-oxide finish

Resilient Flooring Manufacturers List

Congoleum www.congoleum.com Vinyl sheet flooring and tiles

Domco (division of Domco Tarkett Group) www.domco.com Vinyl sheet flooring and tiles

Forbo www.forbo-flooring.com Linoleum sheet and tiles

Mannington Mills www.mannington.com Vinyl sheet flooring and tiles

Nova Distinctive Floors www.novafloorings.com Laminated linoleum surface over fiberboard and cork planks, floating installation

Tarkett www.tarkettna.com Vinyl sheet flooring and tiles

Cork Flooring Manufacturers & Sources

American Cork Products Co. www.amcork.com Prefinished parquet tiles and floating floor planks

Amorim Revestimentos (formerly Ipocork) www.wicanders.com Floating or glue-down laminated cork tiles with UV-acrylic or oil finish

BHK of America www.bhkuniclic.com Snap-together, no-glue, laminated cork flooring with UV-acrylic finish

Expanko Cork Inc. www.expanko.com Cork tiles with wax or polyurethane finish

Korq Inc. (212) 758-2593

Natural Cork www.naturalcork.com Glue-down cork tiles and floating laminated planks with UV-cured acrylic finish

Nova Distinctive Floors www.novafloorings.com Laminated cork planks with glue-down and floating click-lock installation

WECork www.wecork.com Cork tiles, sheets, and floating floors

Polymer (Urethane), MDF, and Vinyl Trim Producers & Sources

Burton Mouldings www.burton-mouldings.com MDF(medium-density fiberboard), polymer, flex, and wood

Fypon www.fypon.com Polymer moldings and components

Nu-Wood www.nu-wood.com Polymer moldings and components

Outwater Plastics www.outwater.com Polymer moldings and components

RAS Industries www.rasindustries.com Polymer moldings and components

Royal Mouldings (formerly Marley Mouldings) www.royalmouldings.com Polymer, polystyrene, expanded-PVC, CPVC, and acrylic molding profiles and components

Flexible Trim Manufacturers & Sources

Flex Trim www.flextrim.com Flexible polymer moldings

Resin Art www.resinart.com Flexible polymer moldings

Industry & Trade Associations for Carpeting, Lighting, Finishes, Wood Products, Flooring, Painting & Decorating

American Lighting Association www.americanlightingassoc.com

Association of the Wall and Ceiling Industries www.awci.org

Carpet and Rug Institute (CRI) www.carpet-rug.org

Drywall Finishing Council www.dwfc.org

Forest Stewardship Program www.fscus.org

FloorFacts www.floorfacts.com

The Gypsum Association www.gypsum.org

National Oak Flooring Manufacturers Association (NOFMA) www.nofma.com

National Wood Flooring Association www.woodfloors.org

Painting and Decorating Contractors of America www.pdca.org Smartwood/Rainforest Alliance www.smartwood.org

-- Adapted with permission from Best Practices Guide to Residential Construction.

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FLOOR, WOOD RADIANT HEAT - guide to installing wood floors over radiant heat systems
RADIANT HEAT - usage guide, strategies for using radiant heat
RADIANT HEAT TEMPERATURES - at the boiler, in tubing, under floors, floor surface, thermostat & control settings
RADIANT SLAB FLOORING CHOICES - wood vs ceramic tile over a radiant heated floor
RADIANT SLAB TUBING & FLUID CHOICES - tubing and fluid choices for radiant heating
RADIANT HEAT Floor Mistakes to Avoid - proper and improper radiant tubing depth in slabs & slab insulation needs - what can go very wrong when the building contractor substitutes brawn for brains
SLAB INSULATION, PASSIVE SOLAR - slab insulation & vapor barrier placement in heated floor slabs
WOOD FLOOR DAMAGE - from radiant tubing run too hot

  FLOOR, LAMINATE PLASTIC
  FLOOR, RESILIENT VINYL or CORK
  FLOOR, WOOD ENGINEERED & LAMINATED
  FLOOR, WOOD SOLID STRIP, PLANK
  FLOOR, WOOD ENGINEERED, LAMINATE, INSTALL
  FLOOR, WOOD FINISHES
  FLOOR, WOOD INSTALLATION GUIDE
  FLOOR, WOOD MOISTURE
  FLOOR, WOOD RADIANT HEAT

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

ASHRAE resource on dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
- 2005 ASHRAE Handbook : Fundamentals : Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
- 2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
  by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
  "2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
- 1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
  "The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
- Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 AShrae Handbook - Fundamentals (Hardcover), Harry J., Jr. Sauer (Author), Ronald H. Howell, ISBN-10: 1931862923 or ISBN-13: 978-1931862929
- 1993 ASHRAE Handbook Fundamentals (Hardcover), ISBN-10: 0910110964 or ISBN-13: 978-091011096
Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Energy Savers: Whole House Systems Approach to Energy Efficient Home Design [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] - U.S. Department of Energy
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
"Insulation: Adding Insulation to an Existing Home [copy on file as /interiors/Insulation_Adding_DOE.pdf ] - ," U.S. Department of Energy - tips on how to do your own check for the presence of absence of insulation in a home
Insulation: Selecting Insulation for New Home Construction [copy on file as /interiors/New_Home_Insulation_DOE.pdf ] - , U.S. Department of Energy - "Your state and local building codes probably include minimum insulation requirements, but to build an energy-efficient home, you may need or want to exceed them. For maximum energy efficiency, you should also consider the interaction between the insulation and other building components. This is called the "whole-house systems design approach" [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] -
Insulation Types [copy on file as /interiors/Insulation_Types_DOE.pdf ] - , table of common building insulation properties from U.S. DOE. Readers should see INSULATION R-Values & Properties our own table of insulation properties that includes links to articles describing each insulation material in more detail.
Lath & Plaster Systems [copy on file as /interiors/LathPlaster_Nat_Gypsum.pdf ] - , 092300/NGC, National Gypsum Lath and Plaster Systems, National Gypsum Corporation, 800-628-4662 describing National Gypsum's Kal-Kore brand plaster base
Pergo AB, division of Perstorp AB, is a Swedish manufacturer or modern laminate flooring products. Information about the U.S. company can be found at http://www.pergo.com where we obtained historical data used in our discussion of the age of flooring materials in buildings.
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Detailed Guide to Installing Wood Floors over Radiant Heating

See these articles on radiant heated floors

Specifications for Installing Radiant Heated Wood Floors over Slab-on Grade

Specifications for Installing Radiant Heated Wood Floors over Thin Slabs

Specifications for Installing Radiant Heated Wood Floors over Staple-up and Panel Radiant Floor eat Systems

Resources: Manufacturers, Industry Associations, & Sources of Indoor Wall Materials, Flooring, Carpeting, Lighting, Sound Control Materials

Drywall Trims and Accessories

Prefinished Wood Flooring

Bamboo Flooring Producers & Sources

Resilient Flooring Manufacturers List

Cork Flooring Manufacturers & Sources

Polymer (Urethane), MDF, and Vinyl Trim Producers & Sources

Flexible Trim Manufacturers & Sources

Industry & Trade Associations for Carpeting, Lighting, Finishes, Wood Products, Flooring, Painting & Decorating

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair