ARDEX Feather Finish XF Underlayment User Manual

: June 14, 2024
: ARDEX

Table of Contents

Feather Finish XF Underlayment
Moisture Evaluation and Testing
Substrate Preparation (Proper Prep™)
Treating Joints and Cracks
Install Appropriate Moisture Control or Priming Course (if needed)
Mixing and Application
Drying Time and Installation of Flooring
Documents / Resources

ARDEX FEATHER FINISH XF®
Self-Drying, Cement-Based Finish Underlayment

Feather Finish XF Underlayment

Provides a smooth surface over a variety of substrates prior to the installation of today’s demanding floor coverings, including sheet vinyl and VCT
Install floor coverings in as little as 15 minutes
Superior coverage – up to 300 sq. ft. per bag*
Mold and mildew resistant
Priming not required for most applications
Exceptional bond strength
Suitable for castor wheels (EN 12 529)
Easy to mix with water only; applies to a true featheredge
Interior use only
Suitable Substrates

Concrete (structurally sound)
Absorbent terrazzo on concrete †
Metal (Interior only and non-aluminum) †, †††
Plywood subfloors (untreated)
Solid hardwood †, †††
Gypsum ††
Properly installed ARDEX moisture control systems on concrete:
- ARDEX MC™ RAPID
- ARDEX VR 98
Other approved, non-porous materials on concrete:†
- Non-porous (non-absorbent) cementitious terrazzo
- Ceramic, quarry or porcelain tiles
- Epoxy coatings
- Epoxy terrazzo
- Non-water-soluble adhesive residue
- Concrete treated with certain curing compounds (test areas only; for full instructions, see ardexamericas.com/services/properprep )

†Must be sound, solid and well-bonded to underlying, structurally sound substrates.
Please note that a skim coat of a cementitious material applied over a non- porous surface may not create a porous bonding surface for the finish flooring and/or may not protect the finish flooring from migration of existing adhesive. Consult the flooring manufacturer for confirmation of any minimum thickness requirements for cementitious underlayments, as well as for any additional considerations, when installing over potentially non-porous surfaces.
††Please be advised that gypsum is inherently weak. This product will provide a solid bonding surface for new flooring, but it cannot correct the weakness of an underlying gypsum surface.
†††It is the responsibility of the installation contractor to ensure the substrate is rigid, well supported, properly anchored and free of undue flex and vibration.
Suitable Applications

All grade levels
Dry areas only
Interior applications only
May be used as an embossing filler over residential sheet vinyl when mixed with ARDEX P 82; see instructions below

Job Conditions
During installation and cure, substrate and ambient temperatures must be a minimum of 50°F / 10°C.”

Moisture Evaluation and Testing

This product is intended for interior, dry spaces. Hydrostatic pressure, plumbing leaks, flood factors and other sources of water infiltration must be identified and corrected prior to installation. This product is not a vapor barrier and will allow free passage of moisture vapor.
Test concrete in accordance with ASTM F2170. For highmoisture floor coverings and adhesives, this product can be installed over concrete with relative humidity (RH) levels up to 95% provided: Each on-ground slab is built on a vapor retarder, which remains effective and intact, in conformance with ASTM E1745.
All other cases: Moisture control is required if the RH exceeds the most stringent of the following: 1) the limitations imposed by the flooring manufacturer; 2) the limitations imposed by the adhesive manufacturer.
If moisture control is required, see “Moisture Control System Selection” section below.
Moisture Control System Selection
For ARDEX MC RAPID: RH levels up to 100% on all grade levels.
For ARDEX VR 98:

RH levels are 98% or below (85% for radiant-heated slabs).
The slab is either above-grade, or, the slab is built on a vapor retarder, which remains effective and intact, in conformance with ASTM E1745.

If moisture control is not required, select applications require priming. See the following section for further details.
Priming Method Selection (select applications)
If a moisture control course will not be applied, priming is needed only for select applications as follows:

ARDEX P 82 ™ Ultra Prime
ARDEX P 4™ Pre-Mixed, Rapid-Drying, Multipurpose Primer
ARDEX P 51™ Primer

Substrate (Interior, dry substrates only; All grade levels)| Priming Course
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Gypsum and extremely absorbent concrete| ARDEX P 51 “double prime” or ARDEX P 4
Metal (Interior only and non-aluminum)| ARDEX P 82; anti-corrosive epoxy coating required for ferrous metals
Epoxy| ARDEX P 82 or ARDEX P 4

Substrate Preparation (Proper Prep™)

For full details on Proper Prep, reference the following articles at ardexamericas.com/services/properprep:

Article 1.1: Preparing Concrete for ARDEX or HENRY Underlayments
Article 1: Preparing Concrete for Bonded ARDEX or HENRY Applications
Article 2: Preparing Wood for Bonded ARDEX Applications
Article 3: Preparing Metal for Bonded ARDEX Applications
Proper Prep Brochure

If necessary, mechanically clean the substrate by shot blasting or similar means. Do not use acid etching, adhesive removers, solvents or sweeping compounds, as these are bond breakers. Sanding is not an effective method to remove contaminants from concrete.
Substrate must be dry and free of excess moisture and alkali. All substrates must be sound, solid and thoroughly clean of all bond-breaking contaminants, including but not limited to: dirt, dust, wax, grease, paints and oils; unapproved curing compounds and sealers; overwatered or otherwise loose or weak material; and unsuitable adhesive residues.
Handle and dispose of asbestos and other hazardous materials in accordance with prevailing regulations, which supersede the recommendations in this document.
Minimum Preparation
In all cases, substrate must be clean; additional prep may be needed, as follows:

Substrate	Minimum Preparation
Non-water-soluble adhesive residue on concrete	Must be scraped to a thin,

well-bonded residue ( rfci.com )
Substrate to receive ARDEX VR 98 / ARDEX P 51| Mechanically remove all adhesive residue, sealers, curing compounds, tiles, mortars and epoxy coatings down to clean, sound, solid
concrete / terrazzo
Substrate must be clean and absorbent (ASTM F3191)
Concrete to receive ARDEX MC RAPID| Mechanically remove all adhesive residue, sealers, curing compounds, tiles, mortars and epoxy coatings down to clean, sound, solid
concrete / terrazzo
Concrete and terrazzo substrates must be clean and prepared to a minimum CSP 3 / maximum CSP 5 ( icri.org )

Vacuuming
Following preparation, thoroughly vacuum to remove all excess dirt and debris.

Treating Joints and Cracks

Under no circumstances should any product herein be installed over moving joints or moving cracks. Honor all moving joints.
If an ARDEX moisture control system will be installed (see “Moisture Testing” section above): All dormant joints and dormant cracks greater than a hairline (1/32”/ 0.8 mm) that will not be honored must be pre-filled with ARDEX ARDIFIX™ Low Viscosity Rigid Polyurethane Crack and Joint Repair and sand broadcasted to refusal in strict accordance with the technical data sheet.

Install Appropriate Moisture Control or Priming Course (if needed)

See the “Moisture Control System Selection” and “Priming Method Selection” sections above to select the appropriate product, if applicable.
Products may need longer drying times with low surface temperatures and/or high ambient humidity. Do not proceed with subsequent steps before product has dried thoroughly.
Moisture Control System Installation (if required)
If moisture control is required, install the selected ARDEX moisture control system, in accordance with the appropriate technical data sheet ( www.ardexamericas.com/products ). To select the appropriate moisture control system, see the “Moisture Control System Selection” section above.
Gypsum and Extremely Absorbent Concrete: ARDEX P 51 “Double Prime”
Make an initial application of primer diluted with 3 parts water by volume. Let the initial application dry thoroughly (1 – 3 hours), and then install a second application of primer mixed 1:1 with water as detailed directly above.
Metal / Epoxy: ARDEX P 82
To prevent rust from recurring, ferrous metals must first be coated with an anti-corrosive epoxy coating. The coating must be installed and allowed to dry thoroughly in accordance with the manufacturer’s written recommendations.
Follow the mixing instructions on the container, and apply with a short-nap or sponge paint roller, leaving a thin coat of primer. Do not leave any bare spots. Back roll with a dry roller to remove excess primer. ARDEX P 82 should be applied within 1 hour of mixing. Allow to dry to a thin, slightly tacky film (min. 3 hours, max. 24 hours).
Metal: ARDEX EP 2000
ARDEX EP 2000 can also be used as a priming option over interior metal substrates. Please contact the ARDEX Technical Service Department for a full recommendation.
Epoxy: ARDEX P 4
Apply a thin, even layer to the substrate using a short-nap roller, sponge paint roller or paintbrush. Allow the primer to dry to a thin, opaque, white film (min. 30 minutes; 70°F / 21°C). Once dry, there is no time limit before the subsequent installation may proceed. However, please note that the subsequent installation should proceed as soon as possible to avoid surface contamination or damage to the primed surface.

Mixing and Application

Recommended Tools
ARDEX T-2 Mixing Paddle • 1/2” (12 mm) heavy-duty drill (min. 650 rpm) • appropriate measuring bucket • Mixing container
Water ratio: 2 1/2 quarts (2.4 L) of clean water per unit; 2 parts powder to 1 part clean water by volume (small batches)
Thickness of Application

Application	Max. Thickness
Small, well-defined areas	Unlimited
All other applications	1/2” (12 mm)

Manual
Pour the water in the mixing container first, and then add powder while mixing with the mixing paddle and a 1/2” (12 mm) heavy-duty drill (min. 650 rpm). Mix thoroughly for approximately 2 to 3 minutes to obtain a lump-free mix. Do not overwater! Additional water will weaken the compound and lower its strength.
Small batches may be mixed by hand. Use a margin trowel, and mix vigorously. Just prior to application on the substrate, the mixture should be stirred again to ensure a creamy, smooth, lump-free consistency.
Please note that for thin applications, the profile of the substrate can affect the flatness and smoothness of the product. The thickness of the application should be calculated based on the surface profile of the substrate and the specified tolerances of the floor covering.
After mixing, apply the product to the substrate with the flat side of a steel trowel to obtain a solid mechanical bond before applying the desired thickness. Apply sufficient pressure to fill all defects and to feather the product onto the subfloor surface.
For installations over ARDEX VR 98, special application procedures are required. Please refer to the ARDEX VR 98 technical data sheet or consult the ARDEX Technical Service Department for a full recommendation.
The pot life of the product is approximately 15-20 minutes at 70°F (21°C). If stiffening or surface skinning occurs within this time, remix before using. Do not add more water.
Wear Surface
This product is not to be used as a permanent wear surface, even if coated or sealed. Install a suitable floor covering material, such as carpet, vinyl flooring, ceramic tile, etc. For concrete floors in warehouses, storage areas, hallways or other areas where a wear surface is required, use ARDEX SD-M™ DESIGNER FLOOR FINISH™.

Drying Time and Installation of Flooring

All dry times are calculated at 70°F (21°C). Drying time is a function of jobsite temperature and humidity conditions. Low substrate temperatures and/or high ambient humidity will extend the drying time. Adequate ventilation and heat will aid drying. Forced drying can dry the surface of the product prematurely and is not recommended.

Wood flooring and highperformance adhesives (epoxies or urethanes):	16 hours
All other applications:	(When hardened) typically 15 – 20 minutes

Notes
Intended for use by professional contractors who are trained in the application of this product and/or similar products. Not sold by ARDEX through home improvement centers. For information on ARDEX Academy trainings, visit ardexamericas.com.
In accordance with industry standards, and to determine the suitability of the products for the intended use, always install an adequate number of properly located test areas including the finish flooring. As floor coverings vary, always contact and rely upon the floor covering manufacturer for specific directives, such as maximum allowable moisture content, adhesive selection and intended end use of the product. If the installation is not proceeding as expected, contact the ARDEX Technical Service Department before proceeding further.
Never mix with cement or additives outside of our written recommendations. Observe the basic rules of concrete work, including the minimum surface and air temperatures detailed above. Install quickly if the substrate is warm, and follow the warm weather installation guidelines available on our website.
Dispose of packaging and residue in accordance with prevailing regulations. Do not flush material down drains. Do not reuse packaging.
Precautions
Carefully read and follow all precautions and warnings on the product label. For complete safety information, please refer to the Safety Data Sheet (SDS) available at www.ardexamericas.com.
Technical Data According to ARDEX Quality Standards
All data based on a partial, in-lab mix. Mixing and testing completed at 70°F / 21°C. Physical properties are typical values and not specifications.

Coverage| Per bag at 1/4” (6 mm): 16.7 sq. ft. (1.5 sq. m)
Per bag at 1/8” (3 mm): 33.3 sq. ft. (3.09 sq. m)
Per bag at skim coat: 100 – 300 sq. ft. (9.2-27.8 sq. m)
Coverage varies with texture of substrate surface.
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Drying Time:| See the “Drying Time and Installation of Flooring” section above.
VOC:| 0
Packaging:| 10 lbs (4.5 kg) bag
Storage:| Store in a cool, dry area. Do not leave units exposed to sun.
Shelf Life:| 9 months, if unopened and properly stored
Warranty:| ARDEX L.P. Standard Limited Warranty applies. Also eligible for the ARDEX/HENRY SystemOne™ Warranty when used in conjunction with select HENRY® Flooring Adhesives. See ardexamericas.com/services/warranties for full warranty details.

Made in the USA.
Copyright 2022 ARDEX, L.P. All rights reserved. Content updated 2022-10-17. Supersedes all previous versions. Latest version available at ardexamericas.com. For technical updates, visit: ardexamericas.com/services /technical-services/techupdates.
Visit www.youtube.com/ARDEX101 to watch ARDEX product demonstration videos. For recommended installation tools, visit DTA USA at www.dtausagroup.com. For easy-to-use ARDEX Product Calculators and Product Information On the Go, download the ARDEX App.

ARDEX Feather Finish XF Underlayment - Symbol 3 ARDEX Americas
400 Ardex Park Drive
Aliquippa, PA 15001 USA
888-512-7339
www.ardexamericas.com