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Stone Failures-Why? Article #7
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 7 Concrete Slabs Without Discontinuous Capillary Pore Structure.

Expansion joints! Expansion Joints! Expansion Joints!

Expansion joints are mandatory to allow the stone assembly including the stone, setting materials, grout and adjacent restricting materials to accommodate moisture and thermal expansion.

Requirements for expansion joint width are:

Minimum inch joint with maximum spacing at 16 feet apart in all directions;

Minimum 3/8 inch joint with maximum spacing at 12 feet apart in all directions;

Minimum inch joint with maximum spacing of 8 feet apart in all directions;

Minimum 1/8 inch joint with maximum spacing of 4 feet apart in all directions.

These rules include all installations on exteriors of buildings, all installations exposed to sunlight or temperature changes, and all installations exposed to moisture.

We recommend doubling the rule for interior applications and caution exceeding these rules.

In addition, expansion joints are required where tile and stonework abut restraining surfaces, such as perimeter walls, dissimilar floors, curbs, columns, pipes, ceilings, handrails, doorframes, and where changes in backing material occur.

Expansion joint through tile and stone installations over structural joints must never be narrower than the structural joint.

All expansion, control, construction, cold and seismic joints in the structure should continue through the tile and stonework including all horizontal and vertical assemblies.

For additional information consult the Handbook For Ceramic Tile Installation, Published by the Tile Council of America, Assembly Method EJ171.

The expansion joint detail has been the center page of the handbook for the past 20 years however was relocated in 1998.

The failure of the installing tile and stone contractor to coordinate and install or have installed by other contractors the correct expansion joints to these requirements and the specifications, contributes to the most failures that occur in California on commercial and institutional projects.

In addition, we are observing large custom homes with no expansion joints and resulting loss of bond of flooring assemblies. The lack of expansion joints is exacerbated by the lack of scarifying the concrete slab prior to installation.

This article is part of 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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