Laying the foundation for good design.
Wood substructures like these create unique problems for flooring replacement, especially if adhesives were used. But as adaptive reuse projects have become more common around the country, a growing range of technical solutions have also become available. “New, thin anti-fracture membranes allow almost any material to be used over old, uneven, or wood-framed substructure, as long as the structural capacity is there,” says Andrew Franz, AIA, LEED AP, principal of Andrew Franz Architect PLLC, a New York-based firm.
Veteran designers note positive experiences with the anti-fracture membranes, yet they also recommend that such underlayments generally remain low on the list of the Building Team’s go-to solutions. Adding layers complicates an already complicated engineering dilemma, they note, and the flooring material must be compatible with any chosen product. “Manufacturer warranties for flooring material must be considered when installing the underlayment,” adds Lotz.
For most projects, Building Teams are unlikely to specify an underlayment except for reasons of improving acoustics between floors. According to Frank Kroupa, technical training director for the National Wood Flooring Association (www.woodfloors.org), Chesterfield, Mo., in multifamily residential and hospitality applications, “almost all floors in high-rises are poured floors, and almost all of them want to dampen sound transmission between floors.” A layer of cork or synthetic acoustic material will usually serve the purpose. Krochmaluk says he uses felt between wood and concrete in his corporate projects. For offices and other applications where sound transmission between floors is not as crucial, the Building Team and client might prefer carpet or carpet tile as a sound-dampening floor finish.
Some adhesives for wood or other flooring contain a soundproofing component, a newer technology that may eliminate or reduce the need for an acoustical layer. Underlayments must also be carefully specified for particular conditions, says Franz, who notes that acoustic underlayments are a routine item for urban residential construction. “We specify water-resistant fiberglass products beneath wet areas, and recycled rubber or fiber membranes beneath other dryer assemblies,” says Franz. He warns, however, that floor failures can result from applying the wrong type of layer.
In spite of the caveats, underlayments do have their place, says Interior Architects’ Lotz, noting they are of great value when properly specified for acoustics, leveling, and aesthetics. “Two of the most durable, high-performing, and sustainable options are gypsum underlayments and self-leveling cementitious products, which can be applied to most types of existing subfloors or concrete structures,” she says. These underlayment types can make the difference in a project with an uneven subfloor.
Adhesives: Multiple concerns. Glues and adhesives must be carefully specified with respect to: 1) interaction with the product backing and subfloor materials, 2) the likely maintenance and operations program, and 3) green design principles, since many formulas contain volatile organic compounds (VOCs) and other powerful chemicals.
With respect to interaction, Mark Quattrocchi, AIA, principal with Quattrocchi Kwok Architects, Santa Rosa, Calif. (www.qka.com), notes that some applications may require high-performing adhesives to combat moisture content and alkalinity in some concrete slabs. As for green design and indoor air quality (IAQ), Quattrocchi adds, “Low-VOC-emission adhesives are critical for sustainable flooring.” Although low-VOCs are nearly an industry norm now, you should still review product literature and specifications carefully for verification.
Carpet tiles present unique problems with regard to adhesives. Some are manufactured with self-adhesive “double-stick” backing, which many designers like Baisch caution against. “Corners may start to come up, so the carpet will not appear solid,” he says. On the plus side, carpet tiles can now sometimes be installed with adhesive “dots” instead of glue, a sustainable option that works well with access floors.
Wood can be installed as a floating floor, but otherwise it requires an adhesive. Building Teams are advised to choose a glue that is strong but not too strong.
When the time comes to replace a floor, it is important to successfully and cleanly remove the covering, says Kroupa: “Otherwise it may be cheaper to put down the new wood directly over the old floor.” He recommends polymer-based adhesives where applicable, as opposed to urethane-based compounds, for two reasons: 1) polymer glues have greatly reduced isocyanate content (a VOC) and 2) they do not interact negatively with urethane-finished wood product. Urethane adhesive will cling to the urethane finish, creating unsightly spots that are nearly impossible to remove.