Durability and shower drain flashing

Just in case you haven’t figured this out yet, I am paranoid about moisture and water damage in the building.

And I think I have good reason to be, considering what I encountered during the deconstruction process.

Water damage can cause serious durability issues, and durability is one of those underrated principles when it comes to green building practices, even though it is so simple: The longer we can make things last, the less resources they require over time, and the more sustainable they are.

LEED for Homes embraces the durability principle with the inclusion of a “Durability Management Process” in their check list. It gets a little dry, but only for one paragraph!

The process consists of “Durability Planning,” identifying and listing the various durability risk factors, and, “Durability Management,” a quality control for the installed strategies that lower or eliminate durability risks. A third party verification should assure that everything is kosher, and if so, one may earn up to three LEED points.

What did you say? Bureaucratic? Come on, they have to make some money somehow! And only three LEED points, max? Don’t get me started on the points!

For us, as the property owners, occupants, and contractor on this project, durability with or without paperwork, with or without points, is a no-brainer, because it directly affects our short- and long-term bottom line.

Interestingly enough, the durability issues tabulated in the LEED for Homes guidelines are all about moisture control measures (and as I would argue, plain common sense):

  • Tub, showers, and spa areas – Use non paper-faced backer board on walls.
  • Kitchen, bathroom, laundry rooms, and spa areas – Use water-resistant flooring; do not install carpet.
  • Entryway (within 3 feet of exterior door) – Use water-resistant flooring; do not install carpet.
  • Tank water heater in or over living space – Install drain and drain pan.
  • Clothes washer in or over living space – Install drain and drain pan, or install accessible single throw supply valve.
  • Conventional clothes dryer – Exhaust directly to outdoors.
  • Condensing clothes dryer – Install drain and drain pan.
Source: Leed for Homes Rating System (January 2008), ID-2, Table 1, USGBC

What a nice segway back to my paranoia and our shower drain!

Unlike the basement bathroom, the 1st floor bathroom is located above a living space. The floor construction of that bathroom has wooden floor joists that could begin to rot if they get wet (see also images above).

The drain of our walk in/barrier free shower is the most likely point where water could get into the floor assembly and leak into the basement living space. We will waterproof most of the bathroom (stay tuned for the next post), but the drain warrants one additional step, a drain flashing, to further reduce the risk of leakage.

The drain flashing is formed and shaped to perfectly fit onto a floor drain assembly. No awkward folds or stretching, unlike trying to do the job just with the waterproofing membrane.

The drain flashing (NobleFlex Drain Flashing) is sandwiched between the drain base and drain clamping ring. Two beads of rubber sealant (NobleSealant 150) on the drain base prevent water from escaping under the flashing.

Last but not least, I can screw that drain strainer back into the clamping ring and adjust it to the right height, so that I have positive slope to the drain from the entire shower area.

The next step is the waterproofing membrane (NobleSeal TS), which will overlap with the flashing (see drawing above) and is again sealed with two beads of the rubber sealant. More on that in the next post.

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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