Lag-Screw – A heavy wood screw with a square head and a coarse thread used chiefly where a bolt would not be suitable.

Laminated – Layers of wood cemented, screwed or nailed together to form a unit. The term is also applied to certain types of flooring made up of pieces of timber laid on edge instead of on their sides.

Landing – A flat platform between a series of steps.

Landing Board or Tread – The first board on a landing immediately over the last riser.

Lane – Any passageway or right-of-way, open from ground to sky, not constituting a street, but laid down upon a registered plan and dedicated to public use.

Lap Siding – Boards used to cover the sides of buildings, the lower edge of one board being lapped over the upper edge of the board below.

Lateral Thrust – That component of a load that is exerted in the horizontal direction.

Latin – A building element made of wood, metal, gypsum or fiberboard fastened to the frame of a building to serve as a plaster base.

Lath – A building element made of wood, metal, gypsum or fiberboard fastened to the frame of a building to serve as a plaster base.

Lavatory – A wash basin. A place providing sanitary facilities.

Leaching – Bringing soluble substances to the surface by the passage of water through a solid such as brick or wood by capillary action. In masonry, leaching often leaves a salty deposit on the surface.

Leader – Defined under “Plumbing Terms”.

Lean-To – A secondary structure appended to a main building and covered with a single slope roof.

Ledger Strip – A strip of lumber fastened along the side of a beam or stun on that joists rest.

Light – A pane of glass.

Lintel – A horizontal structural member (beam) that supports the load over an opening such as a door or window.

Live Load – The aggregate weight of the movable articles in a building or dwelling, such as furniture, appliances, built-in equipment, to that a structure is subjected. The live load also includes the weight of people or occupants.

Load (Dead) – The weight of all construction elements in a building.

Loam – Earthy material containing a proportion of vegetable matter.

Lobby – A public or common entrance space in a building.

Lock Nut – A nut screwed down tightly on another nut preventing the first nut from jarring loose.

Lookout Rafters – Short wood members cantilevered over or projecting from a wall to support an overhanging portion of a roof. 

Loose-Fill – Bulk insulation material, used for walls in older houses and for ceiling insulation.

Lot Line – A building term referring to the line that bounds a plot of ground described as a lot in the title of a property.

Lot Types –

            Corner Lot – A lot abutting upon two or more streets at their intersection.

            Gore Lot – A small triangular lot.

            Interior or Inside Lot – a lot bounded by a street on one side only.

Through Lot – A lot other than a corner lot having frontage on two public highways or streets. (Sometimes called a “merged lot”).

Louver – A slatted opening for ventilation in that the slats are so placed to exclude rain, sunlight or vision.

Lumber – Timber sawn, split or hewn for use.

            Boards – Sawn lumber less than 2 inches thick, 4 or more inches wide.

            Dressed Size – The dimensions of lumber after planning to a smooth surface.

Matched Lumber – Lumber that is edge dressed and shaped to make a close tongue-and-groove joint at the edges or ends when laid edge-to-edge or end-to-end.

Nominal Size – The ordinary commercial size by that timber or lumber is known and sold on the market.

Plank – A broad board, usually more than 1 inch thick.

Rough Lumber – Undressed lumber as it comes from the saw.

Shiplapped Lumber – Lumber that is edge dressed to make a rabbeted or lapped joint.