<P> Another similar skim coating is always done in a process called veneer plastering, although it is done slightly thicker (about 2 mm or 1 / 8 inch). Veneering uses a slightly different specialized setting compound ("finish plaster") that contains gypsum and lime putty . This application uses blueboard, which has special treated paper to accelerate the setting of the gypsum plaster component . This setting has far less shrinkage than the air - dry compounds normally used in drywall, so it only requires one coat . Blueboard also has square edges rather than the tapered - edge drywall boards . The tapered drywall boards are used to countersink the tape in taped jointing whereas the tape in veneer plastering is buried beneath a level surface . One coat veneer plaster over dry board is an intermediate style step between full multi-coat "wet" plaster and the limited joint - treatment - only given "dry" wall . </P> <P> The method of installation and type of drywall can reduce sound transmission through walls and ceilings . Several builders' books state that thicker drywall reduces sound transmission, but engineering manuals recommend using multiple layers of drywall, sometimes of different thicknesses and glued together, or special types of drywall designed to reduce noise . Also important are the construction details of the framing with steel studs, wider stud spacing, double studding, insulation, and other details reducing sound transmission . Sound transmission class (STC) ratings can be increased from 33 for an ordinary stud - wall to as high as 59 with double 1 / 2" drywall on both sides of a wood stud wall with resilient channels on one side and fiberglass batt insulation between the studs . </P> <P> Sound transmission may be slightly reduced using regular ⁄ - inch panels (with or without light - gauge resilient metal channels and / or insulation), but it is more effective to use two layers of drywall, sometimes in combination with other factors, or specially designed, sound - resistant drywall . </P> <P> Drywall is highly vulnerable to moisture due to the inherent properties of the materials that comprise it: gypsum, paper, and organic additives and binders . Gypsum will soften with exposure to moisture, and eventually turn to a gooey paste with prolonged immersion, such as during a flood . During such incidents, some or all of the drywall in an entire building may need to be removed and replaced . Furthermore, the paper facings and organic additives mixed with the gypsum core are food for mold . </P>

When did they start using drywall in houses