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laitancea layer of weak and nondurable material containing cement and fines from aggregates, brought by bleeding water to the top of overwet concrete; the amount of which is generally increased by overworking or overmanipulating concrete at the surface by improper finishing or by job traffic.
laminationthe gluing of two pieces of stone together to produce an edge that can be shaped to create an aesthetic appearance for countertops.
lapthe length by which one bar or sheet of fabric reinforcement overlaps another.
latexa water emulsion of a synthetic rubber or plastic obtained by polymerization and used especially in coatings and adhesives.
latex-portland cement grouta portland cement grout with a special latex additive which results in a less rigid, less permeable grout than regular portland cement grout.
latex-portland cement mortara ‘mixture of portland cement, sand, and special latex additives which is used for bonding tile to back-up material. it is less rigid than portland cement mortar.
latha wood strip or metal mesh, which acts as a background or reinforcing agent for the scratch coat or mortar coat. 
lavaa general term applied to igneous rocks, such as basalt and rhyolite, that erupted from the earth by volcanic action.
layout sticka long strip of wood marked at the appropriate joint intervals for the tile to be used. it is used to check the length, width, or height of the tilework. a common name for this item is idiot stick.
lead buttonslead spacers in the solid horizontal joints to support the top stone until the mortar has set.
leadless glazea ceramic coating matured to a glassy state on a formed article, or the material or the mixture from which the coating is made, to which no lead has been deliberately added.  note: this does not imply that the glaze is nontoxic or that it contains no lead. because of plant practices and conditions, a small percentage of lead,, 0.1 to 0.2% (by dry weight), expressed as lead monoxide, may be present.
lega tile wall running alongside a bathtub or abutment. this term sometimes is used to describe a narrow strip of tile floor.
leveling coatsee plumb scratch.
lewis bolta tapered head wedged in a tapered recess in stone for hanging soffit stones.
lewis holesholes in cut stone for lifting and support during setting of cut stones and sometimes for permanent support. holes are checked for the particular lewis lifting device or hook to be used.
lewis pina pin usually with an eye at the upper end. it is used in pairs to lift cubic sotnes for installation
light duty tiletile suitable for limited pedestrian traffic such as entryways in single family residences.
limespecifically, calcium oxide (cao); also, loosely, a general term for the various chemical and physical forms of quicklime, hydrated lime and hydraulic hydrated lime.
limestonea sedimentary rock composed of calcium carbonate; includes many varieties. (see oolitic limestone, dolomitic limestone, crystalline limestone). limestones that contain not more than five per cent magnesium carbonate may be termed calcite limestone, as distinguished from those that contain between five and 40 per cent magnesium carbonate (magnesium or dolomitic limestone), and from those that contain in excess of 40 per cent as the mineral dolomite (dolostone, formerly known as the rock dolomite). recrystallized limestones and compact, dense, relatively pure microcrystalline varieties that are capable of taking a polish are included in commercial marbles.
linersstrengthening elements attached to the back of stone slabs, usually a structurally sound section of similar stone dowelled and epoxied into place.
lintelthe block of stone spanning the top of an opening such as a doorway or window; sometimes called a head.
lippagea condition where one edge of a tile is higher than an adjacent tile giving the finished surface an uneven apperance
lippingusually refers to flagging materials; caused when two pieces of material to be joined together are slightly warped or twisted causing one or more edges to be higher or lower than the adjoining material.
live loadany load that is not permanently applied to a structure.
load-bearing walla wall designed and built to carry superimposed vertical and shear loads as opposed to nonload-bearing walls.
loss on ignitionthe percentage loss in weight of a sample ignited to constant weight at a specified temperature, usually 900-1000 c.
lug silla stone sill set into the jambs on each side of masonry openings.
lugssee self-spacing tile.