Our roofing company is located in Southern California, where
most houses are roofed with concrete tiles. Until 30 or 40
years ago, almost all roof tiles installed in the United States
were clay tiles, like those used for thousands of years in
Europe and China. In the past few decades, though, concrete
roofing tiles have edged out clay on residential roofs and now
dominate the market.
Roof tiles, whether concrete or clay, are very resistant to
fire. Although some traditionalists prefer clay tiles over
concrete, there is no arguing with the main advantage of
concrete tiles: They cost about half as much as clay (see
"Concrete Tile vs. Clay Tiles," below).
Tile vs. Clay Tile
The main advantage of concrete tiles over clay
tiles is their lower cost. Proponents of clay tiles
usually mention two advantages of clay over
concrete tiles: better colorfastness and longer
The color of a clay tile is not affected by
exposure to the elements; the same cannot be said
of concrete tiles. Although most concrete roof
tiles are manufactured with an integral pigment
that colors the entire thickness of the tile, the
color of concrete tiles will fade over time.
"Concrete tile will never hold its color as well as
clay," says Ken McGee, owner of The Tile Man, a
supplier and installer of concrete and clay roof
tiles in Louisburg, N.C.
Well-made concrete tiles should last a long time,
although probably not as long as clay tiles;
estimates range from 30 to 50 years. By contrast,
many European clay tile roofs are still waterproof
after a century of service. Traditional fired clay,
although relatively easy to break, does not degrade
from exposure to the elements. Because objects made
from fired clay can't burn or rot, they are among
the most durable objects known to archeology. Clay
objects can easily last for thousands of
Although some early concrete roof tiles had
durability problems, especially in areas with
frequent freeze/thaw cycles, most concrete roofing
tile manufacturers claim that today's concrete
tiles are more consistent and durable than ever.
Although there are reports of isolated cases of
seriously deteriorated concrete roof tiles, tile
manufacturers claim that such problems are rare and
occur only when a bad batch of tiles gets through
their quality-control systems.
"A few years ago, I saw a job up in the mountains
where the concrete tile just disintegrated in the
winter," says McGee. "It just fell apart. But that
was unusual. Most of the manufacturers are very
careful. I wouldn't let anyone knock concrete too
much. You don't have to worry about concrete tile
falling apart any more."
— Martin Holladay
Consider the Weight
Standard-weight concrete roof tiles generally weigh between 9
1/2 and 12 pounds per square foot — significantly more
than asphalt shingles, which weigh only 2 1/2 to 4 pounds per
square foot. For houses where weight is a concern, many tile
manufacturers offer lightweight roof tiles weighing 5 1/2 to 7
pounds per square foot. These tiles are made with a lightweight
aggregate, like expanded shale, instead of sand.
If you're reroofing a house with existing asphalt shingles and
you're not sure whether the roof structure is adequate to
support concrete tiles, you should have the roof framing
checked by an engineer before proceeding.
Concrete roof tiles are available in three basic profiles:
mission S-tiles (or "Spanish S"), villa tiles (low-profile
tiles with a double-S shape), and flat tiles, which are often
designed to look like wood shakes or slates.
The job shown in this article used 17-inch-long Spanish
S-tiles made by Eagle Roofing Products (see "Sources of
Supply," page 4 of article). These S-tiles lock together along
the sides, where they form a lap joint.
Tile manufacturers provide trim tiles specifically designed to
complement their various tile profiles. Most roofs will require
at least two different types of tile: standard field tiles and
ridge tiles. For jobs using S-tiles, we trim the ridges, hips,
and rakes with a simple barrel trim tile. Some styles of roof
tile use a rake trim tile that differs from the ridge tiles.
Some manufacturers also offer a "hip starter" tile, a trim tile
designed to be installed as the bottom tile on a hip.
Low-slope installations. In
general, the minimum slope for a tile roof is 3/12. If a
customer insists on installing roof tiles on a roof with a
pitch below 3/12, consult the tile manufacturer for
installation specifications. Low-slope applications will
require a carefully detailed waterproof membrane (for example,
a self-sticking bituminous membrane) under the tiles. In
addition, many tile manufacturers require that tiles on a
low-slope roof be installed using a method that minimizes the
number of fasteners that penetrate the membrane.
With or without battens?
Concrete roof tiles can be either installed on battens parallel
to the eaves or direct nailed to the felt-covered plywood or
OSB sheathing. Here in San Diego, we have had excellent success
direct nailing concrete roof tiles.
Most tile manufacturers permit direct nailing, except on roofs
with a pitch steeper than 7/12 or in very cold climates subject
to ice dams.
When battens are used, they are typically 1x2s, with one
course of battens for each course of tiles. It's important to
leave a gap of about an inch between the ends of adjacent
battens, in order to allow a gap for water to drain. Battens
should be no longer than 48 inches, for the same reason.
Necessary tools. The three
most important tools for installing concrete roof tiles are a
nail gun, a gas-powered cut-off saw or circular saw with a
diamond blade, and a leaf blower for cleaning off the
Prepping the Job
Roof tiles are not completely waterproof; in a driving rain,
some water is likely to get past them. We install the asphalt
felt carefully, because it is the most important waterproof
layer on a tile roof.
Forty-pound felt. Tile
manufacturers require, at a minimum, a single layer of #30
asphalt felt. Because a heavier felt is more durable and holds
up better to foot traffic during tile installation, we always
use #40 asphalt felt. The felt should be installed with a
minimum 2-inch head lap and 6-inch side lap.
To avoid leaks at the sides of dormers, chimneys, and
skylights, we carefully crease the felt and turn it up, rather
than cutting it on the sheathing. For extra protection, we
often use a peel-and-stick flashing membrane at penetrations
such as roof vents, or at tricky areas around chimneys and
On tile roofs, all plumbing vent pipes get two layers of
flashing. The primary flashing, a galvanized steel boot with a
minimum skirt width of 6 inches, is installed at the same time
as the asphalt felt. This flashing is bedded in asphalt roofing
cement and is installed on top of one course of the asphalt
felt, while the next felt course laps over the flashing (see
Each plumbing vent receives two layers of metal
flashing. The primary flashing is galvanized and is
installed at the same time as the asphalt felt (left).
The secondary flashing is installed later, when the
tiles go on. An S-tile roof gets secondary flashings
made of aluminum, which is flexible enough to conform
to the curve of the tiles (right).
While workers are on the roof, it's possible to get a few
unintended holes or rips in the felt. Because the felt, rather
than the tiles, is the roof's waterproof layer, we're always
careful to patch all such tears and holes with felt, roofing
cement, or a high-quality caulk.
Ridge boards and hip boards.
Concrete tile roofs require special nailers at ridges and hips.
These nailers — ridge boards and hip boards — are
lengths of 2-by lumber, installed on edge. The height of these
nailers varies, depending on the configuration of the tiles
being installed. The most common sizes used are 2x3s, 2x4s, and
2x6s (Figure 2). The ridge and hip boards are usually
toe-nailed in place after the roof is felted and then
individually wrapped with additional pieces of felt.
Typically, hip boards — nailers that support the
hip shingles — are 2x4s or 2x6s (left). Hip and
ridge boards are installed after the roof has been
felted and are later separately wrapped with felt