Technical Elements

Tile roofing: a sustainable presence

According to NRCA's 2006-07 Annual Market Survey, tile roofing continues to hold a steady percentage of the U.S. steep-slope roofing market.

There are several probable reasons for tile roofing's sustained presence in the marketplace. One explanation is roofing tiles' durability and fire-resistance properties. Also, tile roof systems are aesthetically appealing because tile comes in a wide variety of shapes, sizes, textures, colors and finishes.

Tile types

Two basic types of roofing tile are available: clay and concrete.

Clay tile is manufactured from high-quality clay and shale deposits. These raw materials are ground into a fine powder and mixed to become a homogeneous mass of the proper plasticity. The clay is then extruded, cut to size, and formed or pressed into various shapes and styles. Top surfaces can be colored or glazed, as well.

Concrete tile is composed of Portland cement, water, and sand or fine aggregate. The materials are mixed and then extruded under high pressure. Various additives may be included during mixing to improve strength, reduce water-absorption properties or control cure time. Cementitious glazes may be used when glazed surfaces are desired. Concrete tile is then put in a kiln to dry.

Clay and concrete tile come in an assortment of profiles. The most common profiles are plain, pan and cover, interlocking (including high, medium and low profiles and flat tiles) and S-tile. Each of these shapes requires specific installation procedures.

Installation guidelines

Clay and concrete tile roof coverings can be installed using several attachment methods; they can be nailed, wire-tied, set in a bed of cement or low-rise foam, or loose-laid.

You should consult several sources before installing tile roof systems. The NRCA Roofing and Waterproofing Manual, Fifth Edition, offers general information and design considerations about the application of tile roofing. Additionally, the Tile Roofing Institute (TRI), together with the Western States Roofing Contractors Association, offers Concrete and Clay Roof Tile Installation Manual for Moderate Climate Regions and Concrete and Clay Tile Roof Design Criteria Manual for Cold and Snow Regions.

Also, several manufacturers and importers of clay and concrete tile provide application instructions.

Building codes

The International Building Code (IBC) and International Residential Code (IRC) contain provisions for tile roof installation. IBC's Section 1507.3.8 and IRC's section R905.3.7 specify applying tile "according to the manufacturer's installation instructions," while also considering climate, roof slope, underlayment and tile type.

However, some authorities specify more stringent requirements. For example, the Florida Building Code requires that tile roofs "shall be fastened in accordance with Section 1609 or in accordance with the Florida Roofing, Sheet Metal and Air Conditioning Contractors/TRI document, Concrete and Clay Roof Tile Installation Manual."

Applicable standards

ASTM International has two standards applicable to clay and concrete roof tile: ASTM C1167, "Standard Specification for Clay Roof Tiles," and ASTM C1492, "Standard Specification for Concrete Roof Tile." These standards address material characteristics and physical properties and establish sampling procedures. Also, both standards contain type classifications based on the tile's profile and address freeze-thaw resistance.

NRCA recommends roof system designers specify clay and concrete roof tile be in accordance with ASTM C1167 and ASTM C1492, respectively.

Become familiar

It appears tile roofing is maintaining its popularity. If you install or are interested in installing tile roof systems, familiarize yourself with applicable building codes, product standards and application guidelines.

Joan P. Crowe, AIA, is an NRCA director of technical services.



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