Q. I am planning to build an anchored stone veneer wall with 4” deep rough, natural stones stacked in a random ashlar pattern. Do I need air space?

A. You need the air space to be solidly grouted to stabilize the uneven stones. The grout pack will shrink and pull away from the building paper (which you have stapled in front of the sheathing, right?). This gap will only be 1/16” wide or so, but it is a continuous slot where moisture can slip down the wall, hit the flashing and weep out of the wall. I recommend 100% cotton rope as weeps for this system.