Siding refers to the materials used to clad the exterior walls of a home or other structure. A "square of siding" is a measurement of siding material. One square of siding is sufficient to cover 100 square feet of wall space. A square of siding is thus sufficient to cover a 10-foot by 10-foot section of exterior wall.

Many forms of residential siding are measured in units of "squares"

Types of Siding

Exterior siding is available in many different types. Common materials for residential siding include wood, metal, vinyl, fiber-cement, masonry and stucco. Siding also comes in many forms, including shingles, planks, panels, blocks and, in the case of stucco, adhesive plaster. While a square of siding can be used as a measurement for almost any siding, it is most commonly used when referring to shingle, plank or panel siding, and less commonly with masonry or stucco.


The calculation of the squares of siding material required is straightforward. Calculate the wall area in square feet, including the triangular areas of any gables. Subtract out the square footage of all doors, windows and other openings in the wall. Divide the total by 100 to yield the number of squares of siding needed. When ordering siding material, be sure to increase this number by 10 to 20 percent to account for waste.

Accounting for Exposure

Certain types of siding, such as wooden shingles and clapboards, are applied in overlapping layers, which complicates the calculation of material requirements. For example, a typical shingle is 16 or 18 inches long, but might have only 4 to 6 inches of "exposure" to the weather, due to the overlapping of shingle rows. Be certain to account for both the stock dimensions and desired exposure when calculating the amount of siding material required.

Example Calculation

Suppose you wish to side a wall that is 10 feet high and 20 feet wide, having 50 square feet of window and door space. You wish to use vinyl siding for your siding material.

Calculate the net wall area for siding as follows: (10 x 20) - 50 = 150 square feet.

You will thus need 1.5 (150 divided by 100) squares of siding material for this wall.

An Example Using Shingles

Suppose now you wish to side the same wall described above, but intend to use shingles. You still need to cover 1.5 squares of wall space. The complicating factor here is to determine how many shingles are needed. Your best bet is to consult with your local home center. They will to tell you how many boxes or bundles of shingles are needed per square, based on the shingle dimensions, and the desired exposure.

Other applications

Like siding, material requirements for roofing are typically referred to in units of squares. The most common type of residential roofing is asphalt shingles. These shingles are typically packaged as three bundles per square for standard thickness shingles. Thicker, laminated architectural shingles are packaged as four, or in some cases five bundles per square. Wooden shingles are also used in roofing, and the shingle exposure length must be taken into account when calculating coverage.