I have a home built in 1996, it's your typical SoCal
stucco box. When it rains heavily, which is admittedly
a rare occurrence, I get wet drywall around the sliding
glass door (vinyl coated aluminum frame). There is a water stain on the
paint about 1" high above the door (at the top), and some larger stains down
the drywall on the sides of the door that taper out toward the bottom.
Clearly, water is getting behind the waterproof paper, settling on top of
the door frame, and then leaching into the drywall.

I've talked with the builder and had them out several
times to locate the source of the leak, but we can't
seem to find the source of the problem. Generally, this happens in
particularly heavy rain with alot of wind. We spent several hours a few days
ago spraying a hose at the stucco all around the door, but we couldn't seem
to duplicate the problem. We originally thought that the flashing around the
door was done incorrectly, however that appears not to be the case after our
water test.

Our test included spraying water directly around the door as well as on
several potential problem areas (speaker wire hole, electrical outlet,
exterior light) and we can't seem to get any water leaks/stains like I see
during a heavy, windy rain. Our only thought is that water might be going
horizontally through the air vent up near the roof. Or, it's possible that
the waterproof paper wasn't installed correctly and we just didn't hit the
right spot with the hose.

Last night, it rained heavily *without* wind and the wall is bone dry today,
as opposed to last week's rain where it was wet and mushy to the touch. I'm
totally stumped.

Anyone have any thoughts on what the problem might be?
Or, any suggestions on what else to look for besides ripping all of the
stucco and drywall out. Is there some kind of detection device available
that I could use to find the origin of the leak?

Any help would be fantastic.

Howard

I have a similar problem and don't really see a solution.
Sliding doors are inherently leaky from horizontal driven
water or air, although they are more or less resistant to
dropping rain.

Driven rain sheets along the window, and builds up as a
puddle at the bottom. If wind won't let this pond run off,
it can build up to submerge channels in lower part of the
door. Either the rail can be flooded (which has to have
free clearance for rollers alowing water pass thru), or
you may have weepage holes (maybe with flaps that possibly
aren't functioning) meant to let water from the rail drain,
but actually reversed in wind pressure.

There are various tweaks you can do yourself to reduce
penetration gaps with screwdriver and caulk. Maybe you
can improve drainage to reduce the wind driven ponding
and maybe you can plant a shrub to slow down the wind.

It's very interesting to observe the door when wind/rain
is coming; pretty amazing how a wall of water pushed
horizontally can exploit gaps leading to channels leading
to exit gaps. You may have more patience than a contractor
to diagnose the real problem.