Problems with glass block windows in a shower

Written by patrick gleeson, ph. d., registered investment adv
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Problems with glass block windows in a shower
Glass block showers are no longer code compliant. (its all clear to me now! glass blocks... image by isatori from

Translucent glass blocks gained popularity as an Art Deco building material in the early part of the 20th Century. Architect Frank Lloyd Wright used glass blocks extensively in earlier residential designs. The blocks enjoyed renewed favour at the mid-century when many builders used them to evoke the glamour of the Art Deco era. Even today, many architects and designers use glass blocks in various ways for residential building. Despite their extended use, glass blocks pose several problems when used in shower areas.

Not Code Compliant

You cannot buy off-the-shelf tempered glass block. The traditional product always comes as "annealed glass," which is the technical name for the glass commonly found in most residential windows. Glass blocks do not meet current International Residential Code (IRC) standards for installation in shower areas. Almost all local U.S. building codes derive from the IRC code, which mandates tempered glass in shower areas because a slip and fall in a shower with an annealed glass door, for example, might break the glass. Sharp shards of heavy annealed glass can inflict serious or even fatal wounds.

"Glass Block for Safety"

Some companies advertise a thicker, solid "Glass Block for Safety." One company, for example, offers a 3-inch solid glass impact and bullet-resistant glass block. Sellers advertise that such a block is "very difficult to break." Nevertheless, this disclaimer does not qualify it for use in shower areas. The codes do not provide for substitutions. A homeowner must apply for a variance from the local building and safety authority. Generally, variance applications to substitute code compliant materials for other materials must include test results from the manufacturer or a recognised testing authority. As a practical matter, many homeowners would almost certainly find these tests unaffordable.

Potential Mold Problems

Older shower areas sometimes used glass block. Even in 2010, and despite the code problem, various online do-it-yourself sites explain how to build your own glass block shower stall. However, in addition to the code restriction, glass block showers present other problems. Mold tends to grow in the wide grout areas between blocks. Tiled shower walls have a waterproof cement board, often called a "green board," behind the tile; if water leaks through the tile grout, the green board prevents the water from penetrating further. A wall of glass blocks has no such backstop, and as the grout ages, water begins to penetrate the blocks. Eventually the water makes its way through to the other side of the blocks.

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