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KEY COURSE. 1. A horizontal row of keystones passing
through the center of an arch. Generally used because the archway is
too deep for a single keystone (or a single transverse row of arch stones)
to suffice. 2. A course of keystones used in the crown of a barrel vault.
KEYSTONE. Wedge-shaped stone at the center of an arch or vault.
KILN. A furnace oven or heated enclosure used for burning or
firing brick or other clay material.
Kiln Run. Brick from one kiln which have not been sorted or graded
for size of color variation
KING CLOSER. A closer to fill an opening in a course, usually
three-fourths the size of a regular brick.
KNEELER. A building stone shaped to change a direction of the
LADDER REINFORCEMENT. Premanufactured reinforcement. Side wires
are connected in a single plane by perpendicular cross wires.
LAP. The distance one masonry unit or reinforcing extends over
LATERAL SUPPORT. Means whereby walls are braced either vertically
or horizontally by columns, pilasters, cross walls, beams, floors, roofs,
LAYING TO BOND. Laying the brick of the entire course without
using a cut brick.
LEAD. The section of a wall built up and racked back on successive
courses. A line is attached to lead as a guide for constructing a wall
LEWIS. Any of several metal devices for lifting stone blocks
in the quarry or mill or for hoisting columns or other heavy masonry
units in construction.
Box Lewis. An assembly of metal components, some or all of which
are tapered upward, that is inserted into a downward-flaring hole (dovetail
mortise) and cut into the tops of columns or other heavy masonry units
LIME. A critical ingredient of masonry mortars and grouts.
Hydrated Lime. Quicklime to which sufficient water has been added
to satisfy its chemical affinity and convert the oxides to hydroxides.
Lime Putty. Hydrated lime in plastic form ready for addition
Quicklime. A hot, unslaked lime. A calcined material, a major
part of which is calcium oxide (or calcium oxide in natural association
with lesser amounts of magnesium oxide) capable of slaking with water.
Slaked Lime. Formed when quickline is treated with water; same
as hydrated lime.
LIMESTONE. Rock of sedimentary origin composed principally of calcite
or dolomite or both.
LINE. The string stretched taut from lead to lead as a guide
for laying the top edge of a brick course.
Line Pin. A metal pin used to attach line used for alignment
of masonry units.
LINER. In the fabrication of stone veneer (principally marble),
the stone bonded to the back of thin sheets to add strength, rigidity,
bearing surface, or depth of joint.
LINING. A wythe of similar masonry that is bonded to an existing
wall to reinforce it.
LINTEL. A structural member placed over an opening or a recess
in a wall and supporting construction above. Lintel may be of steel,
precast concrete, reinforced masonry constrution. (UBC)
LUG. A projection from, or extension of, a building unit that
engages an adjacent unit; for example, that part of a sill that extends
into an adjoining jamb.
LUG SILL. A sill that projects into the jambs of a window or
LISTED or LISTING. Terms referring to equipment and/or materials
which are shown in a list published by an approved testing agency, qualified
and equipped for experimental testing and maintaining an adequate periodic
inspection of current productions and whose listing states that the
equipment and/or material complies with recognized safety standards.
MIW. Masonry Institute of Washington.
MALLET. A short-handled wooden hammer, with a truncated conical
head, used to work stone and to drive mallet-head shaping tools.
MARBLE. 1. A metamorphic rock made up largely of calcite or dolomite.
2. A rock that will polish and that is composed mainly of calcite or
dolomite or, rarely, serpentine.
Artificial Marble. Precast terrazzo.
MASH HAMMER. A short-handled heavy hammer, with two round or
octagonal faces, used to drive hammer-head shaping tools.
MASONRY. That form of construction composed of stone, brick,
concrete, gypsum, hollow clay tile, concrete block or tile or other
similar building units or materials or combination of these materials
laid up unit by unit.
Masonry Cement. A mill-mixed cementitious material to which sand
and water must be added. ASTM C91.
Masonry Chimney. A chimney of masonry units, bricks, stones or
masonry chimney units.
Plain Masonry. Masonry constructed without steel reinforcement,
except that which may be used for bonding or reducing the effects of
dimensional changes due to variations in moisture content or temperature.
Reinforced Masonry. Masonry constructed with steel reinforcement
embedded in such a manner that the two materials act together in resisting
Solid Masonry. Masonry of solid units built without hollow spaces.
MASONRY UNIT. Natural or manufactured building units of burned
clay, concrete, stone, glass, and gypsum.
Height. The vertical dimension of the unit in the face of a wall.
Length. The horizontal dimension of the unit in the face of the
wall. ASTM C43.
Nominal Dimension. A dimension that may be greater than the specified
masonry dimension by the thickness of a mortar joint. ASTM C43.
Shells. The outer walls. ASTM C43.
Exposed Finished. Units whose surfaces are intended to be left
exposed or painted. ASTM C43.
Natural Finished. Units having unglazed or uncoated surfaces
burned to the natural color of the material used in forming the body.
Non-Lustrous Glazed. Units whose surface faces are covered by
an inseparable fire-bonded ceramic glaze of non-lustrous finish. ASTM
Opaque Ceramic Glazed. Units whose surface faces are covered
by an inseperable fire-bonded, opaque, colored ceramic glaze of bright
stain or gloss finish. ASTM C43.
Plaster-Base Finished. Units whose surfaces are intended for
the direct application of plaster. ASTM C43. (Note: Plaster-base finish
units may be smooth, scored, combed or roughened.)
Roughened Finished. Units whose plane die surfaces are entirely
broken by mechanical means, such as wire cutting or wire brushing. ASTM
Salt Glazed. Units whose surface faces have a lustrous glazed
finish from the thermochemical rection of the silicates of the clay
body with vapors of salt or chemicals. ASTM C43.
Sand Finished. Units whose suface faces are covered with sand,
applied either to the clay column in the stiff mud process or as the
lubricant to the molds in the soft mud process. ASTM C43.
Scored Finished. Units whose face surfaces are grooved as they
come from the die. ASTM C43.
Hollow Masonry Unit. One whose net cross-sectional area in any
plane parallel to the bearing surface is less than 75 percent of the
Modular Masonry Unit. One whose nominal dimensions are based
on the 4-in. module.
Solid Masonry Unit. One whose net cross-sectional area in every
plane parallel to the bearing surface is 75 percent or more of the gross.
MASON'S SCAFFOLD. Besides being totally self supporting, the
true mason's scaffold must also carry the load of the masonry materials.
It may be braced on a bridging already erected.
MORTAR. A plastic mixture of cementitious materials, fine aggregate
and water. See ASTM Specifications C270, C476.
Fat Mortar. Mortar containing a high percentage of cementitious
High-Bond Mortar. Mortar which develops higher bond strengths
with masonry units than normally developed with conventional mortar.
Lean Mortar. Mortar which is deficient in cementitious components.
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