Daddy, Why does that house have bags under its’ eyes? ……..Sill’yness
If windows are the eyes of a house then damaged or stained zones under the windows are ‘bags’ under the eyes.
So the ‘bag’ that you see here is simply wet masonry. It is wet from melting snow that has been sitting on the window sill. The water from the snow (or rains at other times of the year) slowly soaks into and seeps through to wet the bricks and mortar joints below. Sometimes it just runs down the surface. But the mortar soaks in the water and holds it. the brick and stone sill faces absorb less, have less initial penetration and the surface will evaporate water and dry out faster. Hence the lighter colour of the wet brick compared to the surrounding mortar.
Now what happens when the sun goes down and the temperature drops. That water freezes. The mortar begins to break down. Eventually it crumbles and falls out. At some point the mortar is repointed. Rarely is the colour matched perfectly and some times there is no match at all.
Now the ‘bags’ are permanent.
The shame of it is that a slightly better sill installation would have kept it all dry and looking like new.
Original blog post on ActiveRain: Link to Blog Post