Managing a lot of a big job like this, we were bound to make some mistakes.  Other than hiring the wrong plumber, most of the mistakes we made were not substantial.

One mistake we made had to do with our exterior stairs.  They are wood framed, covered in stone, and go from the 2nd floor, down to the basement outside entrance.  Some time after we moved in, we noticed some water staining on the plaster ceiling on the underside of the top flight, indicating some water was getting through.

When we built the stairs, we went through great lengths to waterproof them, with flashing in the corners and a substantial Tough Flex barrier.

So how could they leak? Our mistake was installing step lights on three of the steps on the top flight.

We thought it was a good idea for safety, and figured the stone would provide good protection such that if we sealed the edge between the light unit and the stone, it would not leak.

As we discovered, even the smallest cracks in the grout on the stone can allow a lot of water to penetrate.  When we ran a hose such that it formed a waterfall down the stairs, a steady stream of water was leaking through and oozing trough the plaster below.  The solution was to disconnect and remove the lights, and repair the Tough Flex barrier.

Once we repaired the penetration, we repeated the waterfall leak test, and there were no leaks.

The experience serves as important lesson; grouted stone and tile isn’t waterproof. Wherever you install it, if there is anything behind it that can’t afford to get wet, there needs to be a waterproof barrier underneath.  And don’t penetrate a waterproof barrier.  Just don’t.