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rabbeta groove cut into the surface along an edge so as to receive anoter piede similarly cut.
racka metal grid that is used to properly space and align floor tiles.
ragging offthe procedure of spreading damp cheese cloth and pulling it over the tile surface during the tile grouting process in order to clean the tile.
rake or rake linethe inclination from a horizontal direction.
raked jointa joint in a masonry wall which has the mortar raked out to a specified depth while it is only slightly hardened.
random slaba trimmed slab with a width and length that is not preset, but variable within certain limits.
rangea course of any thickness that is continued across the entire face. all range course need not be of the same thickness.
raw glazea glaze compounded primarily from raw constituents, that is, containing no prefused materials. 
rebated kerfan additional cut that countersinks a kerf from the back edge of the kerf to the back edge of another piece of stone for the purpose of additional anchor clearance, it must be shimmed to allow for tolerance in the cut.
receptora metallic or nonmetallic waterproof support for a shower stall. 
recessa sinkage in a wall plane.
reducera trim unit used to reduce the radius of a bullnose or a cove to another radius or to a square. 
refractory concreteconcrete having refractory prop-. erties, and suitable for use at high temperatures (generally about 315 to 1315 c), in which the binding agent is a hydraulic cement.
regleta recess used to receive and secure flashing.
reinforced concreteconcrete containing adequate reinforcement (prestressed or not prestressed) and designed on the assumption that the two materials act together in resisting forces.
reinforced masonryunit masonry in which reinforcement is embedded in such a manner that the two materials act together in resisting forces.
reinforcement, meshsee welded-wire fabric and welded-wire fabric reinforcement.
relative humiditythe ratio of the quantity of water vapor actually present to amount present in a saturated atmosphere at a given temperature; expressed as a percentage.
release agentmaterial used to prevent bonding of concrete to a surface. (see also bond breaker.)
relief or relieveornament in relief. the ornament or figure can be slightly, half, or greatly projected.
relieving archone built over a lintel, flat arch or smaller arch to divert loads, thus relieving the lower member from excessive loading. also known as discharging or safety arch.
repriseinside corner of a stone member with a profile other than a flat plane.
resina chemical product, clear to translucent, used in some coating processes.
returnthe right angle turn of a molding.
return headstone facing with the finish appearing on both the face and the edge of the same stone, as on the corner of a building.
revealthe depth of stone between its outer face and a window or door set in an opening.
ribbonnarrow bands of rock differing to various degrees in chemical composition and color from the main body of the slate or stone; in other words, bands.
riftthe most pronounced (see “grain”) direction of splitting or cleavage of a stone. rift and grain may be obscure, as in some granites, but are important in both quarrying and processing stone.
riprapirregular shaped stones used for facing bridge abutments and fills. stone thrown together without order to form a foundation or sustaining walls.
risethe word “rise” refers to the heights of stone. generally used in reference to veneer stone.
rockthe integral part of the earth’s crust composed of an aggregate of grains of one or more minerals. (stone is the commercial term applied to quarry products).
rock (pitch) facethis is similar to split face, except that the face of the stone is pitched to a given line and plane producing a bold appearance, rather than the comparatively straight face obtained in split face.
rockingham warea semivitreous ware or earthenware having a brown or mottled brown bright glaze. originated in england on the estate of the marquis of rockingham. 
rod sawthe rod saw is one of the newest tools used in the cutting of tile. it is a steel rod approximately 1/s” in diameter. the rod has tungsten carbide particles embedded in the surface. the rod saw is used to cut circles or irregular curves in tile.
roddingreinforcement of a structurally unsound marble by cementing reinforcing rods into grooves or channels cut into the back of the slab.
roman archsemi-circular arch.
rose windowa circular stone window fitted with carved tracery.
rough sawna marble surface finish accomplished by the gangsawing process.
rubbed finishmechanically rubbed for smoother finish.
rubber spacerscross and tee-shaped objects used to space tile on floors or walls. they are manufactured in thicknesses of 1/16″, 1/8″, 1/4″, 3/8″, and 1/2″.
rubber trowelthe rubber trowel used for grouting is a non-porous synthetic-rubber-faced float that is mounted on an aluminum back with a wood handle. this trowel is used to force material deep into tile joints and to remove excess material for a perfect finish.
rubbing stonea carborundum stone that is used to smooth the rough edges of tile.
rubblea product term applied to dimension stone used for building purposes, chiefly walls and foundations, and consisting of irregularly shaped pieces, partly trimmed or squared, generally with one split or finished face, and selected and specified with a size range.
rusticationchamfers or square sinkings around the face edges of individual stones to create shadows and to give an appearance of greater weight to the lower part of a building. when only the horizontal joints are sunk, the device is known as banded rustication.
rustificationrecessing the margin of cut stone so that when placed together a channel is formed at each joint.
rutilea mineral form of titanium oxide (tio2) (tetragonal crystallization), but usually produced chemically for use in ceramics and other products.