The insured had expensive imported slate installed on the third floor deck of his $2.6 MM home.

A major storm produced water leaks through the ceilings and walls that reached into the first floor circular staircase.  Additionally, per the insured, the slate deck now needed to be replaced.   The claim was worth the price of a new Mercedes, so the client needed to know “What really happened…”

The case turned out to have several different issues.The team approach was applied by using both a civil engineer and a general contractor with extensive masonry and tile experience as the GEI experts.   The first issue was the weather.   Everyone agreed that it rained a lot.  The question was just how much is “a lot”.   The research began by checking the precipitation databases.   While this is not a precise science because there were no onsite direct measurements taken, it gave a pretty good picture of what happened.   It turned out that on the date of loss, there were two major periods of rain.   The first lasted for 12 minutes and came down a rate of 19.5 inches per hour (about 3,400 gallons of water). The second major period of rain was 1.7 in/hr over a three hour period (about 1,485 gal/hr).   For comparison purposes, a 3 inch drain line, flowing by gravity, will accommodate about 950 gal/hr, depending on the slope and degree of cleanliness.

The first non-destructive inspection occurred with the insured, his architect, and the contractor present.   A second destructive inspection included the above plus the insured’s attorney.   We observed two drain gratings in the main deck area.  A smaller deck had a single drain grating.   Since the decks were located over the house, the drain pipes were concealed by the walls and ceilings.  The next question was how many pipes, of what size, lead to where?   The significance of this question is that there may have been three separate drain lines, or the three grates may have all emptied into a single drain line.   If it was a single line, then the number of drain gratings was unimportant as the limiting factor would be the capacity of the pipe.

At a second meeting, the contractor furnished the blueprints.   The plans were reviewed and the routes of the pipes were determined.   There were no as-built drawings, so the combination of the original plans and the memory of the contractor had to answer the questions of the number, sizes and placement of the pipe(s).

The total area drained, excluding possible rainfall from the higher roofs directed onto the deck, was 1,750 square feet into one 3 inch diameter drain line.   This was a larger area than allowed by the local building code for a single 3 inch drain pipe.

The next problem was the issue of the drains themselves.   The insured stated that when the heavy rains came, he walked onto the deck and the water was over the tops of his slippers.   Obviously the drains were overwhelmed, the question was why.

The first issue was the adequacy of the drains to receive the volume of water that a continuous normal heavy rain would provide.   The answer was found under the covers.   The elegant copper drain inlet grates were 6 inches by 6 inches.   This appeared to be a generous opening to feed into a three inch diameter pipe.   When we removed the grates for inspection, however, we discovered that the square grate transitioned to a circle that narrowed to a diameter of 1 ½ inches at its narrowest point.   This was entirely inadequate to receive a heavy continuous rain.

The next issue is what happens when there is a temporary storm burst in excess of what the drains can handle?   The answer is there is supposed to be an alternative path for the water to escape.   In this case, no overflow was fitted to the drain, and no scupper drains were fitted to the perimeter walls that surrounded the decks.   This left a 3 foot wide walkway as the primary escape route for the excess water.   Rather than have the deck higher than the walkway so it would drain by gravity if the regular drains were stopped up, the deck was in some places as much as three inches lower than the walkway, leading to a major ponding situation in the event that the regular drains became clogged or couldn’t keep up with a downpour.

Observing that the water would pond in this manner, lead us to several sources of water intrusion into the house, ignoring the deck waterproofing question.   Proper waterproofing was lacking on both sides of the French double doors going into the home from the deck.   Even though the waterproofing was about an inch off the deck, if the water was ponding in this area to about 3” in depth, the water would percolate up through the weep screed, back down behind the waterproofing and then down into the room below.   Other areas where window and door treatments were not properly sealed with heavy caulking were also observed.   Much of the water staining and intrusion was directly below these door sills.

The final issue was that of the slate deck.   The grout was cracking, some of the tiles had come loose, and many of them were flaking badly.   When 25 were tapped at random, 20 gave a hollow sound, indicating they were no longer solidly attached to the deck.   The insured said that the slate could not be repaired or patched due to the unique color, and therefore the entire deck needed to be replaced by the insurance company.   The architect stated that the deck was of a natural slate imported from India.   It was supposed to weather to produce flaking of the surface and the thickness of the slate specified was approximately ¾ inch to 1 ¼ inch with purposely distressed edges.   The actual thickness measured was ½ inch to 5/8 inch on sample pieces removed from the deck.

There were several areas of delamination of the slate tiles.   The thinset used to adhere the tiles to the waterproof membrane had failed and frequently stuck to the back of the tile and not to the weatherproof membrane.   There was no fabric backer between the waterproofing and the thinset, which could have been a cause of the de-bonding. There was also scoring on the membrane and separation of the grout along the edges.   Water had been getting in and under the tiles through the grout and caused the slate to become detached from the waterproof membrane.   Additionally, as the tiles flaked, the residue would have flowed into the drains to further reduce their capacity.

In Summary: the drain capacity for the decks did not meet code, the drain grates were visually appealing but were functionally challenged, the deck was not crowned, it was dished, there were no scuppers or overflows, there were improperly sealed window and door frames, the slate was not the thickness specified, the thinset failed, and the slate purposely produced flakes which would act to clog the drain pipes.

Sometimes you don’t get what you pay for.