Color may be added to the tile. In the color through process, pigments are added so that the color is mixed all the way through the tile. In slurry coating, generally used in warmer regions, a colored concrete top layer is bonded to the uncolored tile base. One-color, blended colors or a combination of shades can be mixed to create uniform or random patterns, giving concrete roof tiles a broader color palette. Multi-color tiles are intentionally manufactured with varying amounts of flashing in differing locations on the tile. This breaks up the potential for monotony and helps to minimize the possibility of vertical or diagonal lines down the roof. In a multi-color tile roof there can be as many as seven to ten different colors with varying shades of color and flashing within one blend.

Roof Tile Profile Classifications

Low Profile Tile − Tiles, such as flat tile that have a top surface rise of 1/2" or less.

Medium Profile Tile − Tiles having a rise to width ratio equal to or less than 1:5

High Profile Tile − Tiles having a rise to width ratio greater than 1:5 (measured in installed condition)

Source: Tile Roofing Institute

Architects should see samples that exhibit the characteristics that they are specifying or, ideally, view an installed roof with the same characteristics they have in mind. The trim tiles that come with field tile are typically manufactured to match the color of the field tiles. Even with stringent quality control standards, product shade variations will occur. This shading, when properly blended throughout the roof, contributes considerably to the uniqueness of every concrete tile roof.

After the extrusion process, the individual wet tiles are cured in a chamber, a process that involves controlled heat and humidity to harden or "cure" the concrete to reach the required strength. The cured tiles are stacked on wooden pallets and packaged for sale. Manufacturers test everything from raw materials to the finished product to ensure both regulatory compliance and internal quality control standards. Other characteristics to note about concrete tiles are flexural strength, water absorption, permeability, and resistance to freeze-thaw cycles.

Ratings
Concrete roof tiles are completely non-combustible and carry an Underwriters Laboratories (UL) Class-A fire rating, the highest fire-resistant rating available; Class- A indicates the roofing can withstand severe exposure to fire originating from sources outside the building. Because tile roofing systems allow air circulation under the tile, they reduce heat transfer to attics during fires. In comparison, most house fires spread because embers ignite roofing materials, accelerating combustion.

Specifying Issues

Aesthetics
Concrete tiles are available in profiles, styles, finishes and colors that can imitate the appearance of clay, slate and cedar shake, replicating centuries-old roofing materials. Regional preferences exist. Popular in northern California, for example, is a technique known as "boosting," which involves stacking barrel tiles on beds of mortar to create a time worn look. In Florida, the classic terra-cotta Mediterranean-style barrel tiles remain a most popular option. Flat tiles are becoming increasingly more popular in the Carolinas and Texas where brick and stone are commonly used in both residential and commercial building.

Efflorescence
A colorfast synthetic iron oxide pigment is mixed throughout the entire thickness of the tile to ensure consistent color distribution and uniform weathering. Occasionally, due to the nature of concrete products, an unpredictable, temporary change in appearance known as efflorescence might take place. It appears as a white haze.

 

"Boosted" tiles are popular in northern California. Photo Courtesy of Hanson Roof Tile

 

 

In order for efflorescence to develop on the surface, three physical conditions must be present. First there must be soluble salts in the material. Second there needs to be moisture coming into contact with the salts and thirdly there must be a path for the soluble salts that are absorbed by the moisture to migrate to the surface. If all three of these conditions are present with the new product, then as the moisture reaches the surface, the moisture evaporates, leaving the salts behind. Concrete, even though it is very hard, contains soluble salts and also has very small pores, which allow the salts in solution to migrate to the surface.

Therefore, efflorescence is possible but does not necessarily occur. The duration of efflorescence, when it occurs, varies greatly and is primarily a function of environmental conditions, such as frequency of rain and drying, exposure and shade. Ultimately, the efflorescence will wash away and the original tile color will again become apparent. Products manufactured at the same time generally effloresce uniformly. In products manufactured at different times efflorescence may occur in a completely different manner. It should be remembered that the efflorescence phenomenon is temporary in nature and that it is a superficial phenomenon that in no way affects the quality or functional properties of roof tile.

Weight
Weighing in at an average of ten pounds per square foot, concrete tiles are heavier compared to asphalt shingles, which weigh about 2-1/2 to 4 pounds per square foot. The added weight of concrete tiles means rafters might have to be reinforced.

However, a concrete tile roof generally weighs no more than three layers of asphalt shingles - a weight which most residential roofs have been designed to support. To be sure, a reexamination of the roof framing systems is advisable, particularly in re-roofing situations. Often, in order to withstand the added weight of concrete tile, a truss or rafter may need to be reinforced; this is a common and inexpensive method to assure a greater load. Lightweight concrete tiles are available, made of an aggregate, and weigh 7.5 pounds or less per square foot; however, they are not as durable compared to standard weight tiles and are more susceptible to breakage from hail, snow and foot traffic.