What Is a Siding Square?
A siding square is a unit commonly used to describe the amount of siding needed to cover a wall. One siding square equals 100 square feet of surface area.
For example, 1,500 square feet of siding coverage equals 15 siding squares. Siding may be sold by the square, carton, box, or individual piece depending on the material and manufacturer.
Gross Siding Area vs. Net Siding Area
Gross siding area is the total area of the walls and other surfaces before subtracting windows, doors, and other openings. Net siding area is the remaining surface that actually needs to be covered after those openings are deducted.
Large openings such as garage doors can make a significant difference in the estimate. However, the mathematical area of an opening does not always translate into an equal reduction in the amount of siding you need to purchase because some cut pieces may not be reusable elsewhere.
What Is Lap Siding Reveal?
The reveal, sometimes called the exposure, is the portion of each siding course that remains visible after the next course overlaps it.
For estimating lap siding, use the actual installed reveal rather than the full width of the siding board or panel. For example, a siding board may be physically wider than the amount that remains exposed after installation.
Why Add a Waste Allowance?
Some extra siding is normally needed for cuts, damaged pieces, corners, gables, and other areas where full pieces cannot always be used efficiently.
Simple buildings with long, uninterrupted walls may produce relatively little waste. Homes with numerous windows, doors, gables, corners, and other architectural features can require more.
Check the Manufacturer's Coverage
Siding package sizes and coverage vary considerably between products. Two cartons of different siding products may contain very different amounts of usable coverage.
When estimating how many cartons or packages to buy, use the coverage stated by the manufacturer for the exact siding product you plan to install rather than assuming a standard package size.