Building Design and Construction

Installation of Thin Coverings

Most manufacturers and trade associations make available instructions and specifications for installation and maintenance of their floorings.
The most important requirement for a satisfactory installation of a thin floor covering is a dry, even, rigid, and clean subfloor.
Protection from moisture is a prime consideration in applying a flooring over concrete. Moisture within a concrete slab must be brought to a low level before installation begins. Moisture barriers, such as 6-mil polyethylene, 55-lb asphaltsaturated and coated roofing felt, or 1⁄32-in butyl rubber, should be placed under concrete slabs at or below grade, and a minimum of 30 days’ (90 in some cases)  drying time should be allowed after placement of concrete before installation of the flooring.

Particular care should be taken with installations on lightweight concrete. It always has a higher gross water requirement than ordinary concrete and therefore takes longer to dry. So a longer drying period should be allowed before installation of flooring. Flooring manufacturers provide advice and sometimes also equipment to test for moisture.
As indication of dryness at any given time is no assurance that a concrete slab at or below grade will always remain dry. Therefore, protection from moisture from external sources must be given considerable attention. (See also Art. 3.4.)
Some concrete curing agents containing oils and waxes may cause trouble with adhesive-applied flooring. Commercial curing agents that have been shown to be satisfactory include styrene-butadiene copolymer or petroleum-hydrocarbon resin dissolved in a hydrocarbon solvent. These products dry to a hard film in 24 hr.
Parting agents, used as slab separators in lift-slab and tiltup construction, may cause bond failure of adhesive-applied flooring if they contain nonvolatile oils or waxes.
Concrete surfaces that have been treated with or have come in contact with oils, kerosene, or waxes must be cleaned as recommended by the adhesive manufacturer.
All concrete surfaces to receive adhesive-applied, thin flooring must be smooth.
Also, they should be free from serious irregularities that would ‘‘telegraph’’ through the covering and be detrimental to appearance and serviceability. For rough or uneven concrete floors, a troweled-on underlayment of rubber latex composition or asphalt mastic is recommended. It can be applied from a thickness of 1⁄4 in to a featheredge. Small holes, cracks, and crevices may be filled with a reliable cement  crack filler.

Wood subfloors, of sufficient strength to carry intended loads without deflection, should be covered with plywood or hardboard underlayments. These should be nailed 6 in c to c in perpendicular directions over the entire area with ringed or barbed nails. The nails should be driven flush with the underlayment surface without denting it around the nail head.
Adhesives commonly used to attach flooring to concrete and underlayment are listed in Table 11.12.

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