Which cracks should be treated?

Any crack will allow moisture penetration into the sub-base, so they should all be treated, with a few caveats: (1) Cracks narrower than 1/8″ should not be filled because there is not sufficient area for the crack filler to penetrate and adhere to the inner sidewalls of the crack. (2) Extensive cracking or “alligatoring” should be patched, not crack filled.