Lets go back to the water thing. How do buildings get wet? Forget about the condensation thing and air leakage and diffusion. Minor compared to rainwater and groundwater. It is all about "how the building touches the sky" and "how the building touches the ground" (Getting Wet I) . Rainwater does not wet a building uniformly. Neither does groundwater, but groundwater is limited to…wait for it…the ground. The top of the building gets the wettest. The corners at the top next. And the very bottom of the building where rainwater splashes up ("splash back") and where the building wicks water up from the ground. Then all you have to add are windows (Getting Wet II). The rainwater is not absorbed by glass, runs down and is concentrated at sills - particularly at the corners ("mustaching"). The window-to-wall interface gets more complicated of course because it is typically a hole-in-the-wall rainwater injection system.

Where a building gets wet it has problems. Guess where all the "repointing" is happening. It gets worse at corners with "pseudo quoin corners".

Wetting Down Low

Buildings really get trashed down low. So we fix them there first because it is easy to get there.