Interior Flooring Manual
Underlayment Panel Selection Lonseal flooring must only be installed over plywood underlayment panels. Plywood panel selection, conditioning, installation, and preparation must conform to ASTM F1482 and APA Document E30. Installations over any other type of underlayment panel, including, but not limited to, Luan, OSB, fiber-cement panels, gypsum fiber panels, particleboard, hardboard, waferboard, MDF, or HDF, can result in installation or performance issues and will not be supported or warranted by Lonseal. Do not attempt to install flooring on plywood panels that are wet, not properly acclimated, pressure-treated, or fire- retardant treated. Do not install flooring on underlayment panels that are fastened or adhered directly to concrete. Underlayment Panel Fasteners Use exterior rated staples or ring shank fasteners, such as annular-grooved or screw shank nails. Avoid resin coated nails and staples, as these items can move within the panel, resulting in nail pops and squeaks. Make sure the fastener length does not exceed the combined thickness of the underlayment and subfloor panels. Use the correct fastening schedule as detailed in the ICC-ES ESR-1539, available at www.isanta.org . Screws are recommended only on panels 3/8 in. (9.5 mm) and thicker. They should be exterior rated, properly spaced, countersunk, and filled with an approved patching compound. Refer to Patching Compounds on page 9.
Note: Never use cartridge-type construction adhesives as a replacement for fasteners when installing underlayment panels. Fumes from some construction-type adhesives can cause discoloration and damage the flooring.
Concrete Subfloors All concrete subfloors must meet the requirements of ASTM F710 and have a minimum density of 100 lbs./ft 3 (1602 kg/m 3 ) and minimum compressive strength of 3500 psi (24.1 MPa). Refer to Concrete Slabs on page 4 for additional information. Steel-troweled Concrete If the concrete has a dense steel-troweled surface, it should be mechanically abraded, by diamond grinding or shot blasting, to provide a surface optimized for adhesion. Cracks and Joints Repair all cracks in new and old concrete. Control joints or large dormant cracks, such as those typically found due to settling, must be cleaned out, opened up with a crack chaser where necessary, and patched with an approved patching compound. Refer to Patching Compounds on page 9. If a crack is too large for patching or extends entirely through the concrete slab, it should be repaired using epoxy injection or another suitable method as recommended by ICRI. Gypsum Concrete Underlayments All gypsum concrete underlayments must meet the requirements of ASTM F2419 and have a minimum density of 105 lbs./ft 3 (1460 kg/m 3 ). The minimum compressive strength must be 2000 psi (13.8 MPa) over wood subfloors or 3000 psi (20.7 MPa) over concrete subfloors. Minimum thickness must be 3/4 in. (19.1 mm) over wood subfloors or 1/2 in. (12.7 mm) over concrete subfloors. Due to the porosity of this type of underlayment, consult the manufacturer to determine if a primer is necessary, prior to application of a patching compound or adhesive.
Note: Use of a gypsum concrete underlayment will require written approval from Lonseal’s Technical Department prior to installation for warranty terms to apply. When contacting Lonseal, the product being used must be submitted for review.
Lightweight Cellular Concrete Underlayments All lightweight cellular concrete underlayments must meet the requirements of ASTM F2471 and have a minimum density of 110 lbs./ft 3 (1682 kg/m 3 ). The minimum compressive strength must be 2000 psi (13.8 MPa) over wood subfloors or 3000 psi (20.7 MPa) over concrete subfloors. The minimum thickness must be 1 1/2 in. (3.8 cm). Due to the porosity of this type of underlayment, consult the manufacturer to determine if a primer is necessary, prior to application of a patching compound or adhesive. Note: Use of a lightweight cellular concrete underlayment will require written approval from the Lonseal’s Technical Department prior to installation for warranty terms to apply. When contacting Lonseal, the product being used must be submitted for review.
LONSEAL ®
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Revised: 9.20.2024
Disclaimer: Printed documents are uncontrolled. Always refer to www.lonseal.com for the most current technical information.
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