Masonry. It’s an ancient form of building material, but there’s an awful lot to learn about it.
One thing that’s important to remember is that masonry (including brick, CMU, stone, and mortar) is porous and absorptive.
Masonry walls that are under construction should be protected from rain and snow (at the tops, and at window openings), so that the masonry wall doesn’t absorb too much water. If saturated masonry is not allowed to dry out before being closed in, moisture-related problems, such as exterior efflorescence, or even interior moisture problems, may occur.
Here’s my latest post about this, and how building codes address this issue, in the brand new Denver Chapter CSI Blog: “Protection of Unfinished Masonry Walls.”