Squares & Coverage

Notes

• Measure your own perimeter before ordering. The 164 ft above assumes a tidy rectangle about 1.5 times as long as it is wide. An L-shaped or U-shaped house of the same 1,600 ft² has 15 to 30% more wall — and the error runs in the direction that leaves you short on the last day.
• The 15% deduction for openings is an average, not your house. A wall of glass on the south elevation, or a house with very few windows, moves it several points either way. If accuracy matters, measure each opening and subtract properly: siding is ordered by the square and the offcuts are not returnable.
• Waste is not padding. Every course has to start and stop at a corner or an opening, and the offcut is usually too short to use elsewhere. A 15% allowance on a average house is normal; gables are the worst because every course is a different length and the angle cut wastes the end.
• Order the trim at the same time. J-channel, corner posts, starter strip, undersill and utility trim are separate items, they are colour-matched to a specific production run, and a later top-up can arrive visibly different. Roughly 208 ft of J-channel and 54 ft of corner post for this house.
• Order everything in one lot number. Colour varies between production runs, and on a large elevation the difference is visible in daylight. This is the single most common regret on a siding job and it costs nothing to avoid.
• Gables are extra and this figure does not include them. A gable end adds roughly half the width times the rise. On a steep roof over a wide house that is easily another square or two, and it is the part most often left out of a quantity take-off.