Dimensions of a Siding Square

Square

• Homeowners are used to pricing materials and installations per square foot, which works well for estimating small projects such as putting a rug in a room, or painting one dining room wall. Contractors are used to working with much bigger projects, such as putting siding on an house. They thus typically use a larger standard of measurement called the “square” when sizing siding or roofing. A square is 100 square feet, which is typically 10-by-10 feet. However, other combinations of length and height are acceptable for the square, such as 20-by-5 feet, as long as they total 100.

Calculations

• To calculate the number of squares needed for a wall of siding, multiply the height by the length in feet, such as 10 feet multiplied by 30 feet, to come up with 300 square feet. Subtract the total square footage of any doors, windows or any spaces that will not take siding. For example, 300 minus 50 square feet is 250 square feet. Then add 20 percent. In this case, 300 plus 20 percent equals 360. Divide the result by 100 to define the number of square. So, 320 divided by 100 equals 3.2 squares.

Types

• According to Consumer Reports, siding comes in four main types. Vinyl combines a low price with low maintenance, making it the most popular siding material. It doesn't require any painting and naturally resists insects and moisture. It can also be colored and made to look like wood from a distance. Plastic shingles and shakes can also look like natural cedar, and require minimal maintenance. Fiber cement is the synthetic that most resembles wood planks. It is insect-proof but can suffer from moisture damage, and thus requires periodic refinishing. Wood shakes and shingles boast traditional warmth and can be cut and stained in different weights. However, it requires the most maintenance because it can be damaged by rot, insects and woodpeckers.

Codes

• The International Residential Code or IRC, which is the foundation for building codes in the U.S., illustrates how standards differ according to the type of siding. For example, for wood shakes and singles, the IRC specifies the measurements as well as methods for application over sheathing in precise detail. For vinyl siding, it mandates following the instructions supplied by the manufacturer. For fiber cement lap siding, it talks about minimum overlaps of 1.25 inches, and caulk-sealed ends for siding without tongue-and-groove end joints.