I have recently run into two cases where the tile stall showers, in new residences, have failed the required "Flood Test" mandated by California State law for Termite Inspectors. I have inspected many new homes with tile stall showers over the years (over 30 years now) and have never had a contractor offer a reasonable challenge to the shower testing method required, until recently. This contractor's contention is that our required test places the water level above the height of the actual waterproofing of the shower. I found him to be intelligent, honest and experienced. In his case, he was a third party brought in to render an impartial opinion. I do not feel he was biased and feel his challenge has some merit. The biggest complaint from a Seller of a home is that stall showers are not intended to be filled to the top with water and that they would not leak during normal use, an understandable complaint.
The standard stall shower test is found in the California Code of Regulations code 1991 (a) (12) and reads as follows; "Repair a stall shower if it is found to leak when water tested for a minimum of fifteen (15) minutes after the shower drain has been plugged and the base filled to within one (1) inch of the top of the shower dam." I have tried to find the history on how we came to have this testing requirement, but have not found the answer. I have verified that the Structural Pest Control Act was written with the intention of not exceeding building code requirement. Standards were to be equivalent and not in conflict with the Uniform Building Code.
The Flood Test noted above is a post construction test and the waterproofing cannot be seen. The showers are typically tested for water-tightness by local building inspectors during construction. Tests are to be performed according to the Uniform Building Code/Uniform Plumbing Code section 411.8.1 as follows; "Shower receptors shall be tested for water-tightness by filling with water to the level of the rough threshold. The test plug shall be so placed that both upper and under sides of the sub pan shall be subjected to the test at the point where it is clamped to the drain." Pictured below is a standard test. (There are flaws in this picture, but still a good picture of a vinyl pan test. Bonus points to you if you identify the flaws). Also, damage can occur to this waterproofing during installation of mortar and tile if the tile setter is not careful. This may be the reason some new showers fail the standard flood test during a termite inspection.
I had always assumed that a standard shower dam was constructed like the picture above, with 4 rows of 2X4 framing (6 inches tall) with only 1/2 to 3/4 of an inch of mortar installed for the tile to mount to. Not always so according to the contractor. In his case (actually both cases) the shower dam was claimed to be constructed with 3 rows of framing (4 1/2 inches tall) with 2 to 3 inches of mortar on the top of the dam to make up the height needed for the tiles. One of my inspectors recently observed a shower during construction which was only 2 rows of framing (3 inches) tall, in which they intended to build up with 2 to 3 inches of mortar on top of the dam for tile setting purposes. The picture he sent me below is of this shower with mortar in place on the sides of the dam, but not the top. Section 411.6 of the Uniform Building Code requires any dam or threshold height to be a minimum of 2 inches above the top of the drain. I would assume this includes the rough threshold and waterproofing to be 2 inches above the top of the drain as well, but it is not clearly defined. It would seem that the top of the drain would need to be less than on inch from the bathroom floor level to allow a 3 inch rough threshold to comply with building code. However, there are exemptions for showers built to comply with ADA standards for handicapped access.
The drawing below shows how the standard test should work, with water filled to within one inch of the top of the dam. It is my guess that this is how the Structural Pest Control Board's shower test was supposed to duplicate the building code requirement of filling the pan with water "to the level of the rough threshold". (Keep in mind, the mortar and tile are decorative. Water passes readily down to the waterproofing below. The vinyl pan material is shown by the red line).
Here is an image of what the contractor suspects is happening when the top side of the dam is built up with a very thick layer of mortar;
There seems to be some variance in how each contractor applies the building code. I also suspect that some building inspectors were seriously overloaded with inspections during the recent housing boom which may have allowed some showers to pass that that did not fully comply with code.
I am still working on communications with the Structural Pest Control Board concerning the shower test requirement. I received an email from the Board Investigator that stated this subject would be a good topic for the next Board meeting. Confirmed proof for the speculation as to why these new showers failed the State test, would require at least partial removal of the tile and mortar of the shower dam to verify the height of the rough threshold and waterproofing, then carefully test the shower again to determine at what point the water reaches the level where leakage begins to occur. If we could demonstrate that the contractor's theory is correct, it may be time to reevaluate the testing standard of the Structural Pest Control Act and change the test requirement. It would make sense that the water level of a shower pan test should not exceed the height of the rough threshold and waterproofing. But after the mortar and tile are installed, it's all speculation as to what that height is. We will probably never come up with the perfect "post construction" test.
I would love to gets some input from contractors and home inspectors on this one.
Thanks
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