How to Calculate the Amount of Siding for Hardiplank

Updated March 23, 2017

Hardiplank (sometimes spelt Hardieplank) is a fibre cement siding board that can resemble wood, stucco or other types of plank siding. It is highly durable, weather resistant and fire resistant, but it is also more expensive than conventional siding. Therefore, estimating the quantity of Hardiplank strips required will help eliminate overage and reduce costs. You can determine the quantity required by first calculating your total coverage area, and then calculating the number of Hardiplanks that will make up that area.

Subdivide the area to be covered into basic geometric shapes, such as rectangles and triangles.

Measure the length and height of each section and multiply the measurements to obtain the rectangular area measurement. For triangular areas, divide that number by two to calculate the triangular area measurement.

Measure any doors or windows in the area to be covered and calculate their respective areas. Subtract the areas of these non-covered elements from their sectional area.

Add all the sectional area measurements to get a total coverage area.

Multiply the coverage area by 1.10 to allow for some overage, required for trimming.

Calculate the coverage area of Hardiplank strip. Hardiplank comes in 12-foot strips of varying, overlapping widths. The exposed portion of the width is called the exposure, and its area or width should be listed in the documentation. Divide the width in inches by 12 to obtain the width in feet, and then multiply this figure by 12 feet to calculate the Hardiplank exposure area for one plank.

Divide the adjusted total coverage area by the Hardiplank exposure area to calculate the number of planks required. If there is any remainder, round up to the next highest integer.

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