General Requirements

Armstrong Flooring resilient flooring can be installed on suspended wood, OSB, or a treated plywood subfloor with a 1/4″ underlayment and a minimum of 18″ of well-ventilated air space below. Armstrong Flooring does not recommend installing resilient flooring on wood subfloors applied directly over concrete or on sleeper-construction subfloors over, on, or below grade concrete. Subfloors must meet local and national building codes. Trade associations, such as the APA – The Engineered Wood Association, offer structural guidelines for meeting various code requirements. Refer to ASTM F 1482 Standard Practice for Installation and Preparation of Panel Type Underlayments to receive Resilient Flooring for additional information.

Underlayments for resilient floors must:

• be structurally sound
• be designed for resilient flooring underlayment purposes
• be a minimum of 1/4″ thick
• have panels smooth enough so that texture or graining will not show through
• resist dents and punctures from concentrated loads
• be free of any substance that may stain vinyl such as edge patching compounds, marking inks, paints, solvents, adhesives, asphalt, dye, etc.
• be installed in strict accordance with the board manufacturer’s recommendations

Underlayment Panel Types

Subject to the board manufacturer’s recommendations and warranties, the following underlayments may be used with Armstrong resilient flooring products.

• Plywood rated as suitable underlayment for resilient floor coverings*
• Poplar or Birch Plywood with a fully sanded face and exterior glue
• Luan Plywood, Type 1 (Exterior)**
• Fiber Reinforced Gypsum Underlayment, Fiber Cement Board & Cementitious Backerboard rated as suitable underlayment for resilient floor coverings

Armstrong Flooring does not recommend installation over the following underlayments.

• Treated plywood (unless covered with a 1/4″ of APA plywood underlayment)
• Particleboard
• Hardboard
• OSB (unless covered with a 1/4″ of APA plywood underlayment)

Underlayment Panel Table

	Plywood, APA Underlayment*, Poplar or Birch Plywood, or Lauan**	Oriented Strand Board (OSB)	Fiber Reinforced Gypsum, Fiber Cement Board, and Cementitious Backerboards	Hardboard and Particleboard
Resilient Sheet, Tile, and Plank	X	Not Recommended***	X	Not Recommended

*APA Trademarked Plywood or Equivalent Agency Certified Plywood rated as suitable underlayment for resilient floor coverings such as tile or sheet vinyl. It should have an Exterior or Exposure 1 exposure durability classification and a fully sanded face. APA plywood underlayment grades recommended for areas to be covered with resilient non-textile flooring are A-C, B-C, C-C Plugged or C-C Plugged EXT when marked “sanded face.” Also, Marine EXT or sanded plywood grades (A-C, B-C, A-D or B-D) marked “Plugged Crossbands Under Face,” “Plugged Crossbands (or Core),” “Plugged Inner Plies” or “Meets Underlayment Requirements.”

**Lauan Plywood when used as an underlayment, should be Type 1 (Exterior). The best grade is BB and the next best is CC, while overlay grade (OVL) is the minimum acceptable face grade. There is a wide variety of quality and species classed as lauan. Some may present severe problems such as discoloration, indentation, loss of bond, or delamination when used as an underlayment.

***Oriented Strand Board (OSB) is not recommended under Armstrong resilient floors unless it is covered with a 1/4″ APA plywood underlayment. OSB is acceptable under Rigid Core flooring and ToughGuard II Modified loose lay. 

Note: Regardless of the type of underlayment used under Armstrong resilient flooring, the responsibility for warranties and/or performance guarantees for the underlayment rests solely with the underlayment manufacturer and/or supplier and not with Armstrong Flooring.

The types of subfloors and underlayment panels described are intended only as a guide and should not be construed as an Armstrong Flooring warranty for these products.

Underlayment Panel Installation

• Armstrong Flooring suggests the panels be lightly butted and not filled or flashed, unless the manufacturer specifically recommends filling the joints.
• It has been Armstrong Flooring’s experience that filling or flashing joints between panels with patches may increase the tunneling and/or ridging over these joints.
• Differences in the thickness of wood panels should be corrected by sanding.
• All wood product panels will change in size with changes in water content. Since panels received from the mill generally have very low moisture content compared to the interior of the building and the structural subfloor, allow the panels to condition to the job site per the panel manufacturers’ recommendations. This will minimize the chance of tunnels or ridges over the underlayment joints.
• Some fasteners for underlayment panels or single-layer subfloor panels are coated with resin, rosin or cement that can discolor vinyl flooring. Coated fasteners should not be used to install underlayments unless you know they will not stain the finished flooring product and you assume responsibility for their use
• Some construction adhesives used to glue subfloors and underlayments can stain resilient flooring. Solvent vapors can distort some flooring. Do not use adhesives to install underlayments unless you know they will not stain resilient flooring. You assume responsibility for their use.

How to Evaluate Fasteners for Staining Potential:

1. “Weave” or “thread” the coated nail through two small cuts 1″ apart in a 2″ x 4″ sample of white vinyl flooring.
2. Smaller coated staples can be laid on both the face and back of the sample and held in place by foil wrapping.
3. The coated fastener must be in direct contact with both the face and back of the flooring sample.
4. Tightly wrap each sample (with coated fastener) in aluminum foil.
5. Place in conventional oven set at 200°F (93.3°C) for one hour.Do not exceed temperature or time recommendation. Do not place in microwave oven.
6. Remove sample from oven and allow to cool.
7. Inspect for staining characteristics of fastener.

Underlayment Preparation

• A wood floor to be covered with a new resilient floor must first be properly prepared.
• Check panels for sources of discoloration such as contamination from paint, varnish, stain overspray or spills, plumbing sealers, asphalt, heater fuel, markers or potential staining agents such as wood or bark not visible on the surface, edge sealers, logo markings, printed nail patterns and synthetic patches.
• Remove old adhesive*
• Cover adhesive, oil or wax residue with an appropriate underlayment. If the residue is tacky, place a layer of felt or polyethylene sheeting over it to prevent a cracking sound when walking on the floor.
• Remove all paint, varnish, oil and wax from all subfloors. Many buildings constructed before 1978 contain lead-based paint, which can pose a health hazard if not handled properly. State and federal regulations govern activities that disturb lead-based painted surfaces and may also require notice to building occupants. Do not remove or sand lead-based paint without consulting a qualified lead professional for guidance on lead-based paint testing and safety precautions. AHF Products does not recommend the use of solvents to remove paint, varnish, oil, wax or old adhesive residues because the solvents can remain in the subfloor and negatively affect the new installation. Whenever sanding, be certain the work site is well ventilated and avoid breathing dust. If high dust levels are anticipated, use appropriate National Institute for Occupational Safety and Health (NIOSH) designated dust respirator. All power sanding tools must be equipped with dust collectors. Avoid contact with skin or eyes. Wear gloves, eye protection and long-sleeve, loose fitting clothes.

Nails and Fasteners Used For Underlayment Boards

• Ringshank nails are the best type for installing underlayment panels. These nails should have rings horizontally around the shank of the nail. The nailing pattern should be that of the manufacturer of the board. Nails should be set flush with the panel and not counter sunk.
• Screw-type nails have rings that spiral on the shank of the nail and tend to back out when traffic occurs.
• Adhesive, resin, or cement coated nails are not recommended by many manufacturers of underlayment panels. Some types of these nails will stain vinyl floors.
• Divergent point or chisel point are the best type of staples to use for installing underlayment panels. The manual type stapler is better than the air powered type which tends to sink the staples too far into the panel. Staples should be set flush with the board.

Wood Strip, Board or Plank Subflooring

These subfloors must meet structural requirements. Regardless of whether the subfloor is single- or double-layer, Armstrong recommends the following:

• If the top layer is tongue-and-groove and the strip wood is 3″ or less in face width, cover with 1/4″ or thicker underlayment panels.
• All others should be covered with 1/2″ or thicker underlayment panels.

NOTE: For additional information on the installation and preparation of wood and board-type underlayments see ASTM F 1482, “Standard Practice for Installation and Preparation of Panel Type Underlayments to Receive Resilient Flooring.”

*Some previously manufactured asphaltic “cutback” adhesives contained asbestos. For removal instructions, refer to the Resilient Floor Covering Institute’s publication Recommended Work Practices for Removal of Resilient Floor Coverings.

Disclaimer

Armstrong Flooring cannot be responsible for:

• joint or texture show-through
• tunneling and ridging over underlayment joints
• discoloration from stain sources in the panel, regardless of the type of underlayment panel used
• underlayment panel problems caused by local climate conditions, basement wall and subfloor construction, or improper installation

We strongly suggest that you secure a written guarantee and installation instructions from the supplier or manufacturer of the underlayment board being used.