Re: Evidence of a rain-shielding function by a cornice

It has been my experience that aside from the peculiar effects of a driving
rain which can blow moisture into, under and up any possible fissure, the
most damage is from  the long persitent drizzle that goes well beyond the
"rain" itself.  The wetness just doesn't stop and little leaks and cracks
just keep leaking in.  Therefore the lower the building, the deeper the
overhang (or cornice) and the gentler the breeze (pushing the moisture
against the wall), the better the protection and less the potential for
damage.  The same goes for roofs.  Except for drains backing up, the
persistent wetting of the surface is probably more damaging that one short
intense wetting.

When I look around structures with overhangs (no gutters), the drip line
generally is found away from the wall, indicating that the water is falling
relatively straight down, enough to form a pattern on the ground.  Then,
splash-back becomes a problem...in cases a big problem if weak masonry or
wood is near the ground.

Also observe the condition of paint on a frame building...best near the top
of the wall, under the eaves, and worse on the bottom, on anything which
projects, and varying according to exposure to wind and sun.

So, below the top story or two, I doubt a cornice will protect the wall of
a taller building very much.  Problem with some cornices is that they
deteriorate from exposure too.  That's why so many of them are torn down by
Local Law chickens.

And I'm very much a believer in microenvironments effecitng the direction
and scouring effect of wind in the city.  Dominant wind direction three
seasons of the year is from the northwest (shifting to south in the
summer).  But just walk around the city with an umbrella on a windy day and
watch where the winds come from: whether you're on an avenue, on a side
street or near a park.  I've seen some spectacular eddies during snowstorms
near Central Park (By the GM tower on 58 Street!), and the scoured stone on
south and east cornices and facades when the wind curls across.  I think
the eddies can be worse than the simple pressure of direct wind due to
turbulence.

I guess I straddle between the one who says yes and the five who say no to
cornice protection.  I say, sometimes.  --Jim