BRUSH INDUSTBIAT TUMBXB COMPANY

Many studies also highlight the importance of using the new 7!(" annriar ringed, brightfinish gypsum board nail recently developed by the Gypsum Association afte-' four years of intensive laboratory research and twcr years of on-the-job testing.

One advantageous feature of this nail is its shorter shank, since the shorter the shank the less wood there is to work on it, and consequentl-v the less chance for nail movement or "creep"-i.e., movement of the nail frictional resistance, the nail has equal or greater holding power than the usual l)(" nails; and the shorter the nail, the less the cfeep.

Even though these two precautions (dry lumber and right nail) are taken, Lloyd H. Yeager, general manager of the Gypsum Association, emphasizes, nail popping can still be built into a wall or ceiling b1' poor workmanship. To avoid potential nail pops like those sl-rown on the accon.rpanying illustrations, Yeager specificalll' stresses the following points: head with respect to the surface of the wallboard. Another salient feature is its annular rings, which give the nail greater holding power. The woocl fibers embed themselves in the rings of the nail, thereby increasing resistance to withclrawal. Bv reason of this

An important precaution to be taken against so-called "nail-popping" in gypsum wallboard installations, according to a recent study by the U.S. Forest Products Laboratory, is the use of sufficiently dry framing materials.

Shrinkage of moist lumber, it was found, has the effect of pulling the nailing surface of the framing member away from the nail head, with the result that the gypsum board is no longer securely held against the framing members. The board then could slide on the shank of the nail, tl.rus exposing the nail head. Hence the FPL recommends that the moisture content of tlre framing lumber, when the wallboard is applied, should be approximately equal to what it will be after the building is occupied.

Average moisture content during boartl application, it was suggested, should be 11 to 13/o in deep south and Pacific coastal area. In dry desert areas, the suggested average moisture content is 7 to 8Vo, and in tlre rest of the country 9 to 1.1.%.

1. Proper Nailing. The workman must not depend on the nail head alone to pull the board up tightly. The area of gypsum board immediately adjacent to each nail must be held in firm contact with the framins with