How much should I buy?
Coverage is provided as a range to accommodate variations in surface porosity. On the roof, smoother surfaces like metal will achieve better coverage rates and require less product. The same applies on the ground. Driveways that are in better condition will absorb less.
How do I calculate square footage?
Square footage is based on multiplying the length of an area x width of that area.
What about non-rectangular areas?
In those instances, you need to break the area down into smaller rectangles. For instance, an L-shaped surface can be broken into 2 smaller rectangles (see illustration below). Add the 2 areas (100 + 200 = 300 sq ft) to get a total.
For areas where you will not apply product, subtract that area from the total.