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Stone Failures-Why? 14 Reasons
Article #1, Article #2, Article #3, Article #4, Article #5, Article #6, Article #7, Article #8, Article #9, Article #10, Article #11, Article #12, Article #13, Article #14

Failure Number 14                 Improper Veneer Installations

Veneer installations are classified as adhered veneer and anchored veneer.

All veneer weighing more than 15 pounds per square foot is required to be anchored veneer. 

Failures occur with anchored veneer when adhesives used, fail and when mechanical anchoring systems are not in conformance with minimum industry standards. 

Failures have occurred with adhered veneer assemblies due to lack of coordination with the lath and plastering contractor installing the scratch and brown coat for the tile and stone veneer assemblies. Soaps and surfactants used in plastic cement used by a lath and plastering contractor will bleed through and discolor limestone and marble. Plastic cement is a weaker mix than our ANSI A108.1 requirements. The purpose claimed by the lath and plastering contractor is to facilitate blowing the mortar on the wall instead of using trowel applied method to be installed through ANSI 108.1.

Lath and plastering contractors want to install #15-screeds which serve to control shrinkage cracking of the scratch and brown coat. The correct screed should be double casing beads over double studs or #40 expansion joint screed when the screed is installed by the lath and plastering contractor. The tile industry ANSI A108.1 does not address screeds and assumes the tile and stone contractor is using wood float strips, and removing the wood float strips and filling with caulking/sealants to work at the expansion joint locations. Spacing for expansion joints are the same for veneer as for horizontal assemblies.  Expansion joints are even more critical on south and west facing sides of the building followed by the east side. The building code requires veneer to allow for differential movement on building exteriors.

The lath & plastering contractor wants to install stucco mesh or paper backed wire instead of 3.4 pounds per square yard expanded metal lath attached directly to studs or 2.5 pounds per square yard attached to studs with solid backing in between the stud and the wire reinforcement. The wire installation cannot bridge over the expansion joint location. Where full stone pattern is being installed, the expansion joints must be coordinated with the lath and plastering contractor for location to accommodate the full stone tile design.

Installation of stone as adhered veneer includes washing the back of the stone to remove dust and changing the water being used frequently.

Where a shade range occurs with the stone selected, pre-blend the stone prior to delivery to the site for installation.

All veneer installations require grout, except at expansion joint locations.

There is no building code approval for an ungrouted installation.

If sealers are used as grout release prior to installation of tile, brick and stone, verification is required if the painter will be installing sealers, and if the grout release is compatible with these other sealers.

In California Title 24 prohibits veneer to be installed above entrance and exit doors to schools and hospitals ½ inch and thicker in dimension. All materials ½ inch and thicker above door installations in schools and hospitals are required to be anchored veneer.

The Uniform Building Code Chapter 14 requires full bond adhesion of veneer and even states back buttering of the tile as part of the approved requirements. References to the word “tile” in the code includes thin-brick and stones that are installed by adhesion.

Spot mounting adhered veneer is not approved.

Stone and tile installed on horizontal windowsills adjacent to reflective glass require expansion joints more often due to the thermal heat buildup from the reflective glass.

Again the reminder waterproofing of the windowsill and positive slope for drainage is required.

Masonry and concrete walls are required to be heavily scarified to remove contaminants such as curing compounds and form releases prior to direct bond installation.

Accent stone used on concrete insets require expansion joints at all locations where the accent stone abut the concrete.

In some parts of the United States, acid rain is a concern and the selection of the stone should consider the acid rain environment.

In some parts of the United States, freeze-thaw conditions are a concern and the selection of the stone should consider the freeze thaw conditions.

I defended a tile and stone contractor on a city hall project in the San Diego area. The first issue was installing glazed wall tile on a dome that was subject to 15 freeze thaw conditions a year.  The tile spalled and was shaling due to moisture freezing underneath the glaze of the tile.  A second issue was polished granite was specified on exterior walkways.  The contractor obtained a release of liability from the City after warning of the dangers of polished surfaces on exterior walking conditions.  I woman slipped and broke her hip.  A lawsuit was filed.  The tile and stone contractor was released from the lawsuit.  The polished granite tile has since been sand blasted to remove the polish.

The third issue was citrus fluids etching the sealer on the granite on the interior lobby from drinks served by open bar during grand opening of the city hall. The project was correctly designed with proper expansion joints as I had met with the architect during the design of the building and assisted in expansion joint layout.

In preparing this article and speech, my first step was to list and review the hundreds of failures and defects we have investigated. I then categorized these negative failures with reminders of what not to do in order to emphasize correct assemblies, when properly installed, will work and perform for the intended usage.

Please work toward successful installations without failures.


This article is the last in a series of articles on Stone Failures (Dec. 2000) by Greg Mowat

Forensic Tile Consultants
9541 Vervain Street
San Diego, CA 92129-3523
(858) 484-8118, Fax 484-8302

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