Natural finish - A transparent finish which does not seriously alter the original color or grain of the natural wood. Natural finishes are usually provided by sealers, oils, varnishes, water repellent preservatives, and other similar materials.

Negative Pressure - Condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas. Under this condition, if an opening exists, air will flow from surrounding areas into the negatively pressurized space.

Neutral Wire - Usually color-coded white, this carries electricity from an outlet back to the service panel. Also see hot wire and ground.

Newel Post - The large starting post to which the end of a stair guard railing or balustrade is fastened.

Nominally Horizontal - At an angle of less than 45° with the horizontal.

Nominally Vertical - At an angle of less than 45° with the vertical

Nonbearing Wall - A wall supporting no load other than its own weight.

Nonferrous Metal - Metal containing no iron, such as copper, brass, or aluminum.

Nosing - The projecting edge of a moulding or drip or the front edge of a stair tread.

Notch - A crosswise groove at the end of a board.

Note - A formal document showing the existence of a debt and stating the terms of repayment.

Nozzle - The part of a heating system that sprays the fuel of fuel-air mixture into the combustion chamber.