In many ways, ceramic-tiled shower walls can be investigated and evaluated in the same manner as clad exterior walls. Both rainwater and plumbed interior water have the same potential to promote decay, deterioration, and fungal growth via unintended breaches in a wall’s water-protective envelope. In all cases, the most severe levels of internal damage generally will be encountered within those wall systems that have been most exposed to water leakage at breaches and voids. Conversely, the less water that flows across such deficiencies, the greater the likelihood that any internal damage will be minor. Further, at all water-exposed walls, deficient transitions at changes-in-plane and changes-in-material tend to be the most common locations of moisture infiltration.
This article demonstrates how industry standard guidelines for the investigation and evaluation of water leakage at exterior walls similarly could be used to appraise leakage behavior properties and associated internal damage within ceramic-tiled shower walls at a residential condominium complex in San Francisco.
Guidelines for Water Leakage Evaluations at Exterior Walls
ASTM Standard E2128 (Standard Guide for Water Leakage of Building Walls) describes recommended methods for determining and evaluating causes of water leakage of exterior walls: “This guide does not address leakage through roofs, leakage below grade, or water that accumulates due to water vapor migration and condensation. It is not intended for use with structures designed to retain water, such as pools and fountains.”
E2128’s authors report: “The evaluation of water leakage …is a cognitive process in which technically valid conclusions are reached by the application of knowledge, experience and a rational methodology to determine the… applicability of findings to similar un-inspected or un-tested locations on the building.”
Despite this standard’s narrow focus on the evaluation of leakage at exterior walls, its basic sampling guidelines certainly can be used to evaluate water leakage behavior properties of comparable building envelope systems – such as roofing membranes and deck/balcony waterproofing – intended to resist rainwater intrusion. In similar fashion, as reviewed below, a cognitive evaluation of the project-wide water-resistive performance of tile-clad shower walls also can be carried out in general accordance with the evaluative strategy of ASTM E2128.
Preliminary Investigation and Findings
Consider a three-building, three-story, wood-framed residential condominium complex constructed circa 2005 in a continuous manner by the same developer, general contractor, and subcontractors. During our investigation of reported cladding and waterproofing failures, homeowners at all three buildings also reported interior leakage that appeared to originate from their neighbors’ bathrooms. Within the 176 dwelling units were 304 shower and tub-shower spaces with ceramic-tiled walls (Photo 1). These tiles were adhered with a thinset bond coat to a cement board underlayment (CBU) installed atop gypsum wallboard (Photo 2).
At all inspected locations, the installer terminated these CBU panels directly at (or as much as 1/4 inch above) the vertical flanges (Photo 3) that project upward from the fiberglass shower pans and tub units. In contrast with these as-built conditions, industry standard methods B412 and B415 published by the Tile Council of America (TCA), show the CBU panel overlapping the vertical flange in a water-shedding manner similar to that seen at exterior lap siding and shingles.
Photo 1 – Removal of loose tiles at the base of this wall exposed water staining and deterioration at the thinset mortar.
Photo 2 – Deterioration behind the loose tiles extended to the gypsum wallboard behind the CBU panels (see Photo 3).
Photo 3 – Per TCA methods B412 and B415, the CBU panel should overlap this vertical flange in a water-shedding manner. (These TCA details also depict an asphaltic or polyolefin “membrane” behind the CBU – also overlapping the flange.)