Got a stone wall built by a mason. He's charging for x number of metres but when I measure it, it comes to 10 metres less.
There are six piers in the wall with a wall meeting one side of four of the piers, and the wall is meeting two sides on the other two piers.
Where the wall meets any pier side, 80% of that side's surface area is covered by the wall.
The mason tells me he is counting this non-visible 80% surface area in his calculations. Is this normal?