Expert: Dan Griffin - 7/15/2008

Question
We're stumped. We have a 2nd floor casement window which leaks with a driving rain. Last week we had 15-20 minutes of horizontal rain battering it and within minutes a 1 inch wide by 6 long strip of the carpet under this window was sopping wet. I wet vac'd a good 2 cups of water out. This window is about 10 years old, Norco brand, in a masonry veneer contruction home.  The windows were recaulked on the exterior in 2006 and seem sealed otherwise.

I had stuck a big ball of tissue inside the casement hardware pocket on the exterior and closed the window tightly since we'd had a leak in the same spot in the past year and wanted to see if water was getting around the window seal and into the casement hardware area and into the wall. The tissue was completely dry.

Stumped, we called a certified thermal imaging specialist to come out. He spent almost two hours with us and we cannot find any moisture except the spot on the floor. Insulation, drywall, framing around window were dry. He checked the attic, adjoining rooms, floor underneath, the adjoining garage attic, everything conceivable and all were dry.  We pulled the carpet back and it was only wet in the slim spot under the window.

We are stumped. He did not charge us, only said call him back when it happens again and he'll look more. In a pouring down rain, nothing is wet, only a driving rain. But why isn't the insulation or wall board wet? The specialist didn't recommend using a garden hose because he said we'd be off on a wild goose chase as hoses can makes leaks where this one might not be leaking.

Do you have any suggestions on what to do? We like to fix problems right away.

Answer
Marie, you've got me stumped.  It sounds as if you have attempted most of the choices.  I assume this is a ground floor window.  It sounds like you do not have a basement.  Here are a few ideas:

I have made up an adjustable spray wand that I can control the heighth and direction  of the water quite well.  It delivers a gentle or hard spray based on pressure.  You could get close enough with some lawn sprinklers.  Adjust the spray so that it only falls on the the brick below the window.  Allow it to run at least a 1/2 hour.  It would be great if it was a windy day, though much harder to control the water.  Raise the water higher to it falls on the bottom of the window, again at least a 1/2 hour.  I agree with your gentleman to not force water with a hard stream with the hose, you are trying to duplicate the rain condition.  You are attempting to make it leak and you are trying to find at what level the problem is.

Brick is not waterproof.  I have no idea of the vintage of your home.  The brick is just a different type of siding being held about an inch away from the building by brick ties abut 2' apart.  The wood stud wall is the structural element of the wall with drywall or plaster on the inside and wood, plywood, or fiber sheathing on the outside.  There should be tar paper or similar on the outside of the sheathing and it is this tar paper that actually sheds the water.  It takes a good carpenter or builder to desgn and install the flashing around a window.  There should be a flashing or tar paper plane to always shed the water to the outside.  I didn't say if, I said when the water gets in.  The brick work should have weep holes around the bottom perimeter slightly below finish floor that allow occasional water to weep and allow air to dry the 1" dead air cavity.  Again, brick work is NOT waterproof.

I suspect the tar paper is damaged, torn, or missing or that the window was poorly flashed.  Water enters the dead air cavity and drops until it finds the entry point.  I suspect you will be removing the brick below the window before you solve this problem.  There have been huge mold problems brought on by bad flashing, etc.  Caulking and waterproofing brickwork might get you by for a while, but there must be a system in place for when the water gets past the exterior defenses.