How does wall thickness (4-inch vs 9-inch) change the brick count?

A 9-inch wall roughly doubles the volume of masonry compared with a 4-inch partition wall of the same face area, which translates directly into a higher brick or block count and more mortar. Most Bangalore homes use 9-inch walls for external and load-bearing walls and 4-inch walls for internal partitions, so calculate each wall type separately rather than applying one thickness assumption to the whole house. Mixing thicknesses without separating them in your input will distort the total.