Expansion Joints
These generally are required where tiles abut restraints, such as walls, curbs, columns, or pipes, and where joints occur in structural backings, such as concrete floors and walls. For interior tile floors covering large areas, expansion joints generally should be inserted every 24 to 36 ft if the mortars are cement based. For roofs and outdoor floors, joint spacing may range from 12 to 16 ft. For interior walls, expansion joints are generally required directly over masonry control joints,
where there are changes in materials, or every 24 to 36 ft.
Joint width should be at least 4 times any expected movement. The width should be at least 3â„8 in for exterior joints that are 12 ft apart and 1â„2 in for those 16 ft apart. These widths should be increased 1â„16 in for each 15 that the actual temperature range may exceed 100F between summer high and winter low temperature.
For interior joints, width should be at least 1â„4 in. In any case, if there is a structural joint in the backing, the tile expansion joint should be at least as wide as the structural joint.
The joint sealant should be a nonsagging type in vertical joints and a selfleveling type in horizontal joints. It should be inserted to a depth of not less than 1â„8 in or more than one-half the joint width. The depth should be controlled by insertion of a backup strip, which should be flexible and compressible, with a rounded surface where it contacts the sealant. Closed-cell foamed polyethylene or butyl rubber is a suitable material for the backup.
(Handbook for Ceramic Tile, Tile Council of America, Inc., 100 Clemson Research Blvd., Anderson, SC 29625.)
PANEL FINISHES
For speedy installation of interior finishes on walls or ceilings, rigid or semirigid boards, some of which require no additional decorative treatment, may be nailed directly to studs or masonry or to furring. For acoustic materials, see Arts. 11.79 to 11.82. Gypsumboard is discussed in Art. 11.26.
Joints between panels may be concealed or accentuated according to the architectural treatment desired. The boards may interlock with each other, or battens, moldings, or beads may be applied at joints.
When the boards are thinner than conventional lath and plaster, framing members may have to be furred out to conventional thicknesses unless stock doors and windows intended for use with panels can be used.
