Scharff_Chap10_6x9-GOOD 9/21/00 11:23 AM Page 315

CHAPTER

10
Clay and Concrete Tiles

T oday’s clay and cement roof products all started to develop thou-
sands of years ago when man discovered the function and durability
of roofs constructed of clay. First appearing in the Bronze Age, sun-
baked tiles were found in Crete adorning the palace roofs of local
rulers. Millenniums later, Greeks learned to fire-bake clay tiles and
applied them to structures as majestic as their renowned temples.

Making Clay Tiles

Clay tile is still among the most popular roofing materials in Europe,
where homes and centers of commerce are designed to last for genera-
tions. Their simplicity of form and shape makes traditional, tapered
mission tiles ideal for funneling and shedding water from pitched roofs.
Modern extrusion and pressed-formed processes and high-tech gas-
fired kilns have replaced the primitive method of shaping clay tiles
over human thighs and then either baking them in the sun or using
wood-fired beehive kilns. With these advances in manufacturing have
come tremendous improvements in performance, quality, and product
diversity.
Today, the manufacture of clay tiles starts with shale that is crushed
to a fine powdery clay. The clay is mixed with water and kneaded, or

315
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316 CHAPTER TEN

pugged, to the consistency of cookie dough. Then, to produce simple

clay tiles, this moist, plastic clay is extruded through a die, like dough
through a cookie press, and sliced into lengths. More complicated
shapes come from pressing the clay into molds. Some ornamental tiles
are even sculpted by hand. The formed tiles dry in a room kept at a
temperature of approximately 90 to 95°F. From there, they go to a kiln
for firing.
For their trip through the kiln, the tiles are either stacked on a
refractory, which is similar to a railroad car, and pulled through a tun-
nel kiln, or laid on ceramic rollers that convey individual tiles through
a roller-hearth kiln.
Regardless of the method, the object is to raise the temperature of the
clay to the point of vitrification, which is about 2000°F. At this point,
the clay minerals lose their individual identity and fuse together.

Coloring Clay Tiles

Clay tiles are available in a wide range of colors. The more sophisti-
cated clay tile manufacturers achieve colors through the careful blend-
ing and mixing of various clays into complex clay bodies. Hues from
ivory and almond to deep reds and browns, apricot to peach and buff
tones, and variegated accents are now available to designers. (See App.
A for a vendor list.)
In addition, these colors can be enhanced by adding natural flash or
variegated effects through the introduction of streams of natural gas
during the firing process. By controlling the timing, frequency, and
location of the kiln flashing, an infinite combination of randomly
flashed tiles can be created for that truly custom, one-of-a-kind color
blend.
Another method of coloring tiles is to spray a thin creamy layer of
clay, called a slip, onto the tile before it is fired. The tile then takes on
the color of the slip. The most dramatic, and most expensive, way to
color tile is with a glaze. The metallic pigments in the glaze, when
fired, melt to a glossy, vitreous, richly colored surface, much like that
found on ceramic tile used indoors.
Premium clay roof tiles ensure protection from the elements and
offer extended warranty periods. Some manufacturers offer lifetime
warranties and even include fade coverage.
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CLAY AND CONCRETE TILES

317
Clay tiles offer the homeowner and roofing contractor numerous
advantages:

■ Tile roofs typically last 50 years or longer and do not rust or oth-
erwise deteriorate.
■ The color and texture of most tiles is integral and of natural
materials that do not fade.
■ Tile roofs are more insulating. Clay and concrete tiles resist the
passage of heat gain from summer sun and winter heat loss.
■ The mass of tile roofing provides superior insulation from
sound.
■ Tile roofs are noncombustible and protect the structure from
burning embers without suffering irreparable damage. Tile and
cement roof products carry Class A fire ratings.

Designing Tile Shapes

The roofing industry generally separates roof tile designs into three cat-
egories: high profile, low profile, and flat. High-profile tiles are the
familiar mission, barrel, S, or Spanish-influenced styles (Fig. 10-1).
They are available in a variety of integral and applied colors.
According to legend, the curved shape of high-profile tile evolved
in ancient times when craftspeople formed wet clay sections over their
knee to provide added stiffness. These primitive tiles were probably
baked in the sun or placed in wood-fueled fires.
Low-profile tiles are manufactured in numerous different styles by
several manufacturers (Fig. 10-2). They are also available in a variety
of colors that complement any architectural style.
Flat clay tiles have a shingle shape and are ribbed to simulate
wooden shakes or colored to represent slate. Many of the flat clay tiles
feature an interlocking system.
Also available are special clay tile shapes (Fig. 10-3). For instance,
closed-ridge end tiles and gable-terminal tiles are designed for gable
roofs. Hip-terminal tiles are intended for decorative purposes and are
used where a ridge and two or more hips intersect. Graduated tiles of
diminishing widths are used for round towers, circular bays, and
porches. Tile manufacturers furnish graduated tiles in all popular
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 318

Top view of tile

Nailhole
Overlay
Head of tile

Waterlock Nose
Hip

Nailhole Water course

Head of tile
Overlay

Waterlock Nose
Hip
Water course
Nailholes
Overlay

Nose
Cover
Waterlock Water course

Pan

Underside view of tile

Head lugs Weather checks

Nose lugs
Head lugs

Weather checks

Head lugs Nose lugs

Weather checks

Nose lugs
F I G U R E 1 0 - 1 High-profile S tiles.
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CLAY AND CONCRETE TILES

319

F I G U R E 1 0 - 2 Low-profile tile.

6"
21/2"
21/2"

20" 20" 18" or 20" 161/2"

71/2"
2 1 /8" 13"

A High profile B High profile C High profile

17" 17"
123/8"
123/8"

D Low profile E Flat profile F Low profile

F I G U R E 1 0 - 3 Special clay tile shapes.

shapes. Some manufacturers also offer special valley tile, manufac-

tured in angular or round form, and other special shapes for particular
applications.

Making Concrete Tiles

Concrete tiles are relatively new compared to clay tiles. Although con-
crete tiles have been used in Europe and Australia since the mid-
1800s, they have enjoyed widespread use in the United States only
since the mid-1960s.
Concrete tile is composed of portland cement, sand, and water, mixed
in varying proportions. These materials are mixed and extruded on indi-
vidual molds under high pressure to form the tile product.
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320 CHAPTER TEN

Coloring Concrete Tiles

Concrete tiles are colored by one of two methods. The first is to add
iron or synthetic oxide pigment to the batch mix. This produces a uni-
form color all the way through the tile. A less expensive method is to
coat the tile with a slurry of cement and iron-oxide pigment. This tech-
nique also allows the manufacturer to add highlights of a second color,
which creates a shaded or variegated effect.
The particular coloring method used is dictated by several different
requirements. The first of these relates to cosmetic and aesthetic
appeal. The color-coated product gives wider color hues, while the
body-colored product is less spectacular, is more subdued in appear-
ance, and has a limited color range.
Application requirements for both product types relate primarily to
atmospheric and climatic conditions, as well as aesthetic and archi-
tectural intent. Experience has shown that the surface-coated product
is, generally speaking, more resistant to growth of, and discoloration
from, moss and lichen, found in tropical areas with high humidity and
in areas with large amounts of rainfall.
On the other hand, the color-coated product does not fare well in
areas with extreme freeze and thaw conditions or where there is a large
amount of industrial pollution that contributes to such phenomena as
acid rain and deposits of atmospheric dirt and grime. The through-
color product is more resistant to freeze and thaw conditions and more
subject to discoloration and staining by moss, lichens, and atmos-
pheric pollution.
With either coloring method, the tiles are usually sprayed with a
clear acrylic sealer. The sealer helps the tiles cure properly. It also con-
trols any efflorescence, which is the white powder consisting of free
lime that surfaces as concrete ages. The acrylic sealer forces the lime
out the underside of the tile, where it doesn’t spoil the appearance.
As a side effect, the sealer gives the tile a slight gloss. This gloss
wears off in a few years, and the color softens to its true matte finish.

Designing Tile Shapes

Concrete tile has three classifications: flat, roll, and graduated. Flat
tiles vary in size and have the appearance of slate or wooden shakes.
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CLAY AND CONCRETE TILES

321
Some of these tiles are made of fiber-reinforced cement and come in
various colors. They can be installed on roofs up to 40 feet high in
areas with wind speeds up to 80 miles per hour (mph). Some flat tiles
are available with interlocking water locks.
Roll tile is pan and cover shaped. It is better known as barrel or mis-
sion tile. Graduated tiles of diminishing widths are used for round
towers, circular bays, and porches. Some tile manufacturers furnish
graduated tiles in all popular shapes.

Preparing the Roof

A new roof must receive the same preparation whether clay or con-
crete tiles are to be applied.

Matching Roof Slope and Underlayment

Roll or flat tile can be applied to roof decks with slopes of 4 inches per
foot or more when a minimum of one layer of 30- or 43-pound felt is
applied horizontally to serve as the underlayment, and the tiles are
nailed or wired with a minimum 3-inch headlap.
Any style of clay or concrete tile can be applied on solid-sheathed
roof decks with slopes less than 4 inches per foot when a minimum of
two layers of 30- or 40-pound nonperforated, asphalt-saturated felt are
set in hot asphalt or mastic to serve as the underlayment. One layer of
a modified-bitumen-coated sheet, with laps either torched or heat-
welded, is also acceptable.
Over the underlayment, install vertical lath stringers with horizon-
tal battens fastened over the stringers. This creates a simulated surface
over which the tile can be installed. The tile must be installed with a
minimum 4-inch headlap.

Preparing Deck Surfaces

If plywood is used as the deck material, use exterior plywood thick
enough to satisfy nailing requirements. Separate the plywood panels
by at least 1⁄16 inch to allow for expansion. If wooden planks are used
for the roof deck, the boards should be a minimum of 1 × 6 inches and
should span a maximum of 24 inches between trusses or rafters.
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322 CHAPTER TEN

When the roof deck is made of concrete, a surface must be provided

onto which the tiles can be applied. To create this surface, run 1-×-2-
inch, beveled wooden nailing strips of treated lumber from the eaves
to the ridge. Embed the strips in the concrete and space them 16 or 24
inches on center.
Nail the felt to these nailing strips. Then nail lengths of lath,
applied vertically, directly into the beveled nailing strips through the
felt. Finally, nail 1-×-2-inch battens, or stringers, spaced according to
the type of tile to be used, horizontally across the lath. This simulates
a wooden surface that can accommodate the application of tiles. Some
concrete tile manufacturers also produce special wiring systems for
securing concrete tile to concrete roof decks.

Working with Tiles

When working with tiles, keep the following precautions in mind.

Broken tiles. More tiles are broken in transit and on the ground than
are broken on the roof. Therefore, take great care when unloading
tile at the jobsite. Unload the tile as near as possible to the building,
and distribute it so that delivery to the roof is convenient. Save tiles
that have been broken either in transit to the roof or during appli-
cation. Use these tiles when cut tiles are required.
Loading tiles. To prevent tiles from breaking or becoming soiled, stack
them not more than six high. Keep nails, cement, and coloring
material covered until needed.
Cutting tiles. When tiles must be cut, mark the desired break line on
the tile. Then carefully cut along this line. If too much tile is cut
at once, the tile can fracture. The correct cutting procedure
requires that the tile be placed on a tile stake well back from the
cutting line and tapped with a hammer. Further trimming should
be done with a large pair of pincers. Tile saws or power saws also
can be used to cut tiles. Diamond-tipped tile saw blades are best
for this process.
Narrow tiles. Concrete tiles less than three-quarters of the width of a
full tile are susceptible to wind damage when used on gable ends.
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CLAY AND CONCRETE TILES

323
Drill an additional nail hole in the top of the tile and place a dab of
roofer’s mastic under the butt end. Mechanically fasten the tile
through the newly drilled hole. Gable-end partial tiles installed in
this manner can withstand the same windy conditions as the field
tile.
Drains. To avoid choking drains with broken tile or tile trimmings, do
not permanently install drains until tiling work is complete. Keep
drain outlets covered when tiling to prevent any debris from clog-
ging the leader pipes.

Making Allowances for Cold Weather

Freeze and thaw conditions are encountered in many areas of the
United States. A freeze and thaw area is defined as one that experi-
ences 30 cycles of freezing and thawing per year. One cycle encom-
passes a change in temperature from more than 32°F to less than 30°F
that is accompanied by moisture that freezes into ice and thaws to a
liquid state.
Freeze and thaw failure can occur in just about every product,
manufactured or natural, that is exposed to such conditions. Dry, cold-
weather temperature fluctuations above and below freezing have little
or no effect on concrete tile.
To protect tile from freeze/thaw conditions, apply a minimum of one
layer of 40-pound coated felt horizontally with a minimum 4-inch
headlap and 6-inch sidelap. Slopes below 4 inches in 12 require a func-
tional built-up roof (BUR), a modified bitumen roof (MBR), or a self-
adhering, ice-and-water-shielding bitumen membrane underlayment
system.
In addition to the 40-pound underlayment, the following is
required as an ice shield, regardless of slope, on eaves and barges, or
rakes. Starting from the eave and barge to a point 36 inches beyond the
inside wall line of the structure, use one layer of 40-pound coated felt
set in roofer’s mastic or cold-process adhesive, or one layer of self-
adhering, ice-and-water-shielding bitumen membrane.
Over the underlayments or decks, fasten a vertical counter-batten,
at least 1 × 2 inches, at a minimum of 24 inches on center from the
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324 CHAPTER TEN

eaves to the ridge. Over the vertical counter-batten, fasten a second

horizontally installed batten, at least 1 × 2 inches, spaced to ensure a
minimum 3-inch tile headlap. Use only treated lumber.
This counter-batten system minimizes condensation by allowing
air circulation and, with proper ventilation, helps prevent ice-dam
buildups. A minimum 4-inch tile headlap is recommended in areas
with heavy snowfalls.

Arranging Colored Tiles

Blending modern colored clay and concrete tiles can be a rather diffi-
cult procedure. To guard against a spotted colored roof, mix tiles in the
correct color arrangement on the ground and then send them up to the
roof in bundles along with strict application instructions. For exam-
ple, if the color scheme calls for 10 percent of one color, 30 percent of
another color, and 60 percent of a third color, send the tiles up to the
roof in bundles of 10 tiles, with each bundle having one tile of the first
color, three of the second color, and six of the third color.
In this way, the tiles can be applied in the order in which they were
bundled, and no time is wasted selecting colors on the roof. Separate
the 10-tile bundles into two stacks of five tiles each when loading
them onto the roof deck.
After 75 to 100 tiles have been installed, visually inspect the
applied tiles from ground level and at a distance from the building to
ensure that the tile courses follow straight and true lines and that the
colors of the tile blend well. Repeat this procedure at regular intervals
during installation to ensure an attractive and acceptable roof. The
blending of tile shades to avoid streaks or hot spots is particularly
important. Preblended tiles can be obtained from some manufacturers.
Discuss quality control of material shading and uniformity of tile
with the manufacturer, architect, and building owner prior to contract
and prior to placing an order for the product.

Fastening Tiles
Use nails and screws to hold clay and concrete tiles to decks. Use 3⁄16-
inch compression spikes for concrete decks and No. 12 TEK screws for
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CLAY AND CONCRETE TILES

325
steel decks. On a plywood deck, use ring-shank nails of sufficient length
for slight penetration through the underside of the deck. For board plank
decks, use smooth-shank nails at least 11⁄2 inches long that do not pene-
trate the underside of the deck. For gypsum plank and nailable concrete
decks, use stainless steel or silicon-bronze screw-shank nails of a length
sufficient to penetrate 1⁄2 to 3⁄4 of their length into the deck. Do not pene-
trate the underside of the deck. If the deck is excessively hard, use
smooth-shank nails.
Fasteners also can be used to hold tiles. Do not drive home fasten-
ers or draw the tile. Drive fasteners to a point where the fastener head
just clears the tile, so that the tile hangs on the fastener. When tiles are
fastened too tightly, they lift up at the butt. This allows high winds to
blow them off the roof or to blow water under them. On exposed over-
hangs, the fasteners should not penetrate the sheathing.
Drive all fasteners into the roof sheathing and not between sheath-
ing joints. This is especially important near the top and sides of the
roof. When battens are used, drive all fasteners into the batten boards.
Fasten tiles individually. Secure hip and ridge tiles with one nail in
each tile and with a golf-ball-size dab of roofer’s mastic under the tile
at the headlap, recessed so that it does not show. Barge or verge tiles,
when available, require two nails and roofer’s mastic.
Table 10-1 gives the nailing procedures for attaching clay and
concrete tiles to plywood and wooden sheathing. Battens should
consist of a nominal 1-×-2-inch approved material spaced parallel
with the eaves to achieve a minimum 3-inch tile headlap. Use battens
over solid sheathing and an approved underlayment. Make provi-
sions for drainage at a maximum of every 4 feet past or beneath the
battens. Battens must be attached with four corrosion-resistant fas-
teners per batten.
Over concrete decks, use wire tying strips instead of battens to
secure the tiles. Secure angular strips of wire, 11⁄2 × 1⁄2 inches in size,
to the concrete deck with expansion bolts. Perforate the wide flange
of the wire strip with holes spaced at regular intervals suitable to the
tile exposure. Then run 14-gauge tie wire through these holes and tie
it around the holes in the tile covers. Turn up the wire and twist it
under the lap of the succeeding tile.
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326 CHAPTER TEN

TABLE 10-1 Attachment of Tiles to Sheathing

Field tile nailing
Nailing for
Solid perimeter
sheathing tile and tile on
Solid sheathing without cantilevered
Roof slope with battens battens1 areas2
3/12 to and
including 5/12 Not required Every tile Every tile
Above 5/12 to Every tile every Every tile Every tile
less than 12/12 other row
12/12 and over Every tile Every tile Every tile

1. Battens are required for slopes exceeding 7/12.

2. Perimeter nailing areas including three tile courses but not less than 36 inches from either
side of hips or ridges and edges of eaves and gable rakes. In special wind areas, as desig-
nated by the building official, additional fastenings might be required.

When tiles are attached directly to metal purlins, fasten them

with No. 14-gauge, rust-resistant wire or self-tapping screws with a
minimum 7⁄16-inch-diameter head. If self-tapping screws are used,
they should be capable of penetrating a minimum of 3⁄4 inch into the
purlins.
Either nail or wire each ridge and hip tile in place. If tiles are to be
wired in place, lace No. 14-gauge rust-resistant wire through the nail
holes in the tiles and securely tie it to the heads of nails driven into the
ridge or hip boards (Fig. 10-4). A golf-ball-size dab of roofer’s mastic is
required at the tile headlap. Recess it so that it does not show.
On all roofs, over all roof slopes, and under all conditions, securely
fasten all tiles installed on cantilevered sections of the roof, such as
gables or eaves, and all tiles installed at the perimeter of the roof.
Where tiles overlap sheet metal, secure them with appropriate tie-wire
systems.
Nails for tile roofs should be made of No. 11-gauge, rust-resistant,
aluminum, copper, yellow metal, galvanized, or stainless steel and be
of sufficient length to penetrate either 3⁄4 inch into the sheathing or
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CLAY AND CONCRETE TILES

327
Twisted-wire system
for all types of clay .050" stainless
and concrete tile for steel or 16-gauge
slopes 2/12 and up electrogalvanized
over any deck material steel or 14-gauge
including insulation copper or brass

.050" stainless steel or 16-gauge

galvanized steel, or 16-gauge
brass deck anchor. Seal anchor
completely with membrane-
compatible roofer's mastic after
installation of the twisted wire
F I G U R E 1 0 - 4 No. 14-gauge rust-resistant wire.

through the thickness of the sheathing, whichever is less. On exposed

overhangs, nails should not penetrate the sheathing.
When specifications require that all tiles be embedded in plastic
cement, cover all lateral laps with cement. Use approximately 40 pounds
of cement per square. Continuously embedding tiles in plastic cement
throughout the roof restricts roof movement. Cracked tiles can result
because of the expansion and contraction of the roofing during changes
in temperature. This method of application is not recommended.
Where building officials have designated their localities high-wind
hazard areas, special fasteners must be used. In these wind hazard areas,
secure the nose end of all eaves-course tiles with hurricane clips (Fig.
10-5). Hurricane clips are available in different shapes to suit the type of
roof sheathing used. Lay the tiles
with a minimum 3-inch headlap.
Nail each tile to the roof sheath-
ing with one No. 11-gauge, rust-
resistant nail with a minimum
5
⁄16-inch-diameter head. Apply a
bead of roofer’s mastic over the Use one per
nailheads that fasten gable, barge, tile on sidelap
and ridge tiles. F I G U R E 1 0 - 5 Hurricane clips.
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328 CHAPTER TEN

On extremely steep or vertical roofs, wind currents can cause tiles

to rattle. The recommended method for preventing rattling is to use
hurricane clips. Another way to prevent tile rattling is to set the butt
edge of each tile in a dab of roofer’s mastic. Be careful not to stain the
surface of the exposed tile.

Applying Flashing
Basic tile flashing is applied in much the same manner as for slate and
wooden shake roofs, which is fully described in Chaps. 8 and 9. For
valley flashing, use at least 28-gauge, corrosion-resistant metal and
extend it at least 11 inches from the centerline of the valley each way.
Form a splash diverter rib, as part of the flashing, not less than 1 inch
high at the flowline. Overlap flashing at least 4 inches. Valley metal
and flashing should be in place prior to tile application.
For other flashing, use at least 26-gauge, corrosion-resistant
metal. At the sides of dormers, chimneys, and other walls, extend
the flashing at least 6 inches up the vertical surface. Thoroughly
counterflash and extend the flashing under the tile at least 4 inches.
Turn the edge up 11⁄2 inches.
Long runs of flashing material
at parapet walls (Fig. 10-6) and
copings, where roof tiles come to
Counterflashing an abrupt termination, can be
made of rigid materials, such as
Flashing
26-gauge, galvanized sheet metal.
If rigid materials are used, form
them in such a way that they pro-
vide sufficient coverage and ade-
quate drainage. Establish an
acceptable windblock at longitu-
dinal edges of flashings by grout-
ing the longitudinal edges with
Tile
Felt portland cement mortar or by
Deck using alternative materials accept-
F I G U R E 1 0 - 6 Flashing material at para- able to local building officials.
pet walls. Flashing around roof penetrations
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CLAY AND CONCRETE TILES

329
should be in place prior to the application of tiles. Flashing metal
should be at least 28-gauge, galvanized metal or an equivalent noncor-
rosive, nonstaining material.

Installing the Tile Roof

Examine the areas and conditions under which the tile is to be
installed. Do not proceed until unsatisfactory conditions have been
corrected. To avoid later disputes, report any such conditions to the
contractor and other subcontractors in writing, and keep these letters
on file. Verify that deck surfaces are clean and dry. Remove all foreign
particles from the substrate to assure proper seating and to prevent
water damage. Install the specified tiles in strict accordance with per-
tinent local code requirements.
On vertical applications, and on extremely steep pitches where
wind currents can cause lift, set the butt of each tile in a bead of the
specified plastic cement or sealant, or provide copper hurricane clips
at intervals. Carefully use plastic cement and sealant. Avoid smearing
the exposed tile surface.
Chalk horizontal and vertical guidelines on the membrane to assure
watertightness and proper appearance. Space the chalklines by mea-
suring the delivered tiles for average length and width exposures. Do
not exceed an average exposure length of 1⁄4 inch.

Applying Flat Tiles

Mark off the roof horizontally. Vertical lines, marked off randomly,
help maintain a good vertical alignment. For roofs with pitches of 4/12
and above, install 91⁄2-inch eave blocking, which is available from the
manufacturer, eave metal, a bead of sealant, and 43-pound felt. Lay the
felt parallel to the eave metal and extend it 1⁄4 inch over the lower edge
(Fig. 10-7). Note that some local building codes require an ice-and-
water shield along the eaves.
For roofs with pitches below 4/12, install 12-inch eave blocking,
eave metal, and a minimum 3-foot-wide strip of ice-and-water
shield along all the eaves. Lap the felt 5 inches instead of the stan-
dard 33⁄4 inches and install battens that are notched 8 inches on cen-
ter (Fig. 10-8).
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330 CHAPTER TEN

Stagger tile On reroofs, or when the eave

courses fascia is not raised, install eave
blocking with a cant strip and use
Underlayment new eave metal.
1  2 battens When laying out the roof,
Eave-riser install a ridge nailer (vent).
metal with Next, strike lines that are cen-
weep holes
tered on each hip, if applicable.
F I G U R E 1 0 - 7 Flat-tile application, Then strike the horizontal line
pitches 4/12 and above.
for the top edge of the first bat-
ten 131⁄4 inches above the eave
for a typical 153⁄8-inch tile to ensure proper fit of the bottom row of
tile. Next, strike the horizontal line for the top edge of the last bat-

Note: mortar contact is made with 3 tiles

The head of one tile

The underlock side of one tile

10" mason trowel

full of type M mortar And the underside of
the tile being laid

Overlap Nail here (when required)

Half tile

Eave drip Fascia

Thickbutt tile Mortar bed and

point to finish
F I G U R E 1 0 - 8 Flat-tile application, pitches below 4/12.
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CLAY AND CONCRETE TILES

331
ten so that the field tile butts the ridge nailer (vent), which is
approximately 1 inch below.
Then divide the distance between these two lines into equal incre-
ments not to exceed 12 inches and strike lines for the top edges of the bat-
tens. If different eave lines do not allow for equal spacing, overlap the
bottom row to allow the second row to match the rest of the equally spaced
rows. If a short row is required, lower the height of the eave fascia board
and use 1⁄2-×-16-inch battens with 1-inch spacing for the bottom row. Doing
so allows less than a 10-inch exposure on the bottom tile without causing
the second row to lay at a different pitch from the rest of the tile.
If different ridge heights do not allow for equal spacing, add a
short row along the shortest ridge. If a short row is required, cut off
the head of the tile, drill a new nail hole, and install a thicker batten
tight to the ridge nailer so that the short row maintains the same pitch
as the rest of the tile.
Install hip nailers to within 6 inches of the bottom corner and then
install the horizontal, 1-×-2-inch batten strips, leaving 1-inch spaces
between the ends. Use pressure-treated 1-×-2-×-8-inch battens with
notches or ports 16 inches on center. On pitches 4/12 and above,
install with 18 fasteners.
On 3/12 to 4/12 pitches and vented cold-roof applications, use
pressure-treated 1-×-2-inch-×-6-foot battens with notches or ports
every 8 inches; install with 14 fasteners. Use noncorrosive fasteners of
sufficient length to fully penetrate the roof sheathing. Another
approved procedure is to use 1-×-2-inch horizontal batten strips, with-
out notches, installed over 1-×-2-inch pressure-treated vertical battens
16 inches on center or 1-×-4-inch horizontal battens installed over
1-×-2-inch, pressure-treated vertical battens 24 inches on center. When
using vertical battens, remember to raise the eave and fascia metal to
the additional thickness of the vertical batten.
For flat tile on gable roofs, put an X on the third batten above the
eave, 35 inches on center, starting at the left gable edge. Randomly
place stacks of four tiles above each X on every other batten. Then
stack four more tiles randomly on top of the existing stacks to get a
good color blend across the entire roof position. Put one barge on each
batten next to the gable edge and install with gable tile or later from a
ladder or staging after the field tiles are in place.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 332

332 CHAPTER TEN

Ridge nailer to be of
sufficient height to
maintain even plane
of ridge tiles

Wood sheathing

30-pound felt min.

on wood sheathing
and wrapped over
ridge nailer
F I G U R E 1 0 - 9 Installation of ridge trim.

To lay flat tile on hip roofs, place the Xs at 35 inches on center on

the third batten above the eave and stack the tile above each X. Add
extra stacks along the hip and valley to allow for 11⁄2 tiles per row to be
cut on each side.
Install ridge trim as the roof progresses. Lay the trim with approxi-
mately a 17-inch exposure and seal between the laps with mortar (Fig.
10-9). In fact, fill all hip, ridge, and other voids with American Society
for Testing and Materials (ASTM) C-270 Type M cement mortar and
neatly point it.

Applying Roll Tiles

When roll or mission tile is applied, an under-eaves course of tile does
not need to be applied. Apply the first course of roll tile above an
eaves strip. This metal eave-closure strip, better known as a birdstop,
is specially formed to fit the underside of the tile. They are fastened
11⁄4 inches back and inside the cover of the tile. Apply the balance of
the tile with the head of the tile aligned with the horizontal guidelines.
Tile spacing may need to be adjusted to provide a uniform exposure.
The procedure for installing mission tile varies according to the tile
design and size. Each manufacturer covers the specifics in its installa-
tion instructions. Basically, as with clay and concrete flat tiles, the roof
is first felted and then horizontal and vertical guidelines are chalked to
indicate the courses. Layout is critical because any deviations stand
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 333

CLAY AND CONCRETE TILES

333
out against the pronounced vertical pattern. If the tile is designed with
lugs to hang on battens, nail those battens next. Some manufacturers
approve of hanging their tiles on spaced sheathing over heavy felt
underlayment that is draped over the rafters. Load the tiles on the roof
so that they are evenly distributed and within easy reach.
Extend the first row of tiles 1⁄2 to 11⁄4 inches over the eaves. For
example, when a 133⁄4-inch tile is used, strike the first horizontal
guideline 12 to 123⁄4 inches from the eavesline. Where chimneys or
dormers project through the roof, loosely lay the first course of tile
along the eaves. To minimize tile cutting, secure the tiles to the eaves
only after making adjustments for the projections.
Cut or weave tiles installed down each side of a valley. Valleys can
be open, mitered, swept, rounded, or closed with special tile. Special
valley tile produces much the same effect as the rounded valley tile. It
is longer than regular tile and fan-shaped. Because of its shape, valley
tile need not be nailed, but should be cemented at the laps.
When valley tiles are used, first extend a row of tiles up the val-
ley. Tiling then should proceed back toward the valley from the
verge or gable. The last tile should be large and trimmed against the
valley tile.
Fit tiles that converge along the hips of a roof close against the hip
board. Make a joint by cementing the hip tile to the hip board with
roofing cement or mortar. Color the cement to match the tile. Notch
these cut tiles and either nail or wire them to the hip board. It is advis-
able to lay a golf-ball-size dab of roofer’s mastic between the tiles.
Begin the hip roll with a hip starter, which is a hip roll with one
end closed, or a hip stack, which is a stack of hip roll pieces equal in
height to the hip stringer. Nail the hip-starter tile to the hip board
with nails of appropriate length and follow with the regular hip roll,
lapped either 3 inches or in accordance with the manufacturer’s
requirements. Cement between the laps. Do not fill the interior spaces
of hip or ridge rolls with pointing material, as this material inhibits
air circulation.
Cover ridges in much the same manner as hips. Fill the spaces
between the tiles in the top row with special ridge fittings or with
cement mortar colored to match the tile. When tile fixtures are used at
the ridge, nail the diagonal half of a 2 × 4 on either side of the ridge
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 334

334 CHAPTER TEN

board to provide a nailing surface for the tile fixtures. This is not
required when portland cement mortar is used as fill material between
the last course of tile at the ridge.
Some tile manufacturers make batten strips available for these lay-
outs, while others provide detailed drawings with which contractors
can make their own battens.

Spanish or S Tile Designs: Mark off the roof vertically and horizon-
tally. Interlocking unlugged tile can be laid with a minimum 21⁄2-inch
headlap. Lugged tile should maintain a 3-inch design for mortar appli-
cation. Check with the manufacturer of the particular tile.

Prefabricated Birdstops or Eave Closures: Prefabricated eave closure

strips or mortar can be used to elevate the butt end of the first, or eave,
tile to attain the proper slope. When using mortar, provide weep holes
next to the deck to allow proper drainage of any moisture accumula-
tion under the tiles. Place a full 10-inch mason’s trowel of mortar
under the pan section of each tile, beginning at the head of the tile in
the preceding course. Press each tile into the interlocking position so
that the cover rests firmly against the lock of the adjacent tile.
Installation details for eaves, ridges, gables, and so forth are given
in Fig. 10-10.

Two-Piece Roll or Barrel Mission Layouts: Mark off the roof vertically
and horizontally. Maintain a minimum 31⁄2-inch headlap. Use mortar
or prefabricated eave-closure strips or birdstops to elevate the butt end
of the first, or eave, tile to attain the proper slope. Provide weep holes
next to the deck to allow proper drainage of any moisture accumula-
tion under the tiles.
For roof pitches of 3/12 and steeper, provide a minimum of one
layer of 30-pound felt or upgraded material. Install a birdstop or a
1-×-2-inch wooden strip to boost the first course of tile. Then install
the first row of tile leaving a 3-inch overhang. Use one corrosion-
resistant nail not less than a No. 11-gauge, 5⁄16-inch head per tile or a
tile-tie system. Then lay a booster tile above the birdstop or eave strip,
followed by the starter tiles. Other details necessary for laying a bar-
rel/mission roof are given in Fig. 10-11.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 335

CLAY AND CONCRETE TILES

335
Tile Counterflashing

Felt Flashing
Cement mortar

Tile
Felt

Birdstop or 12
3" wooden strip
m
76m Eave detail Flashing detail at wall
Ridge tile Mastic cement between
ridge tiles typ.
Cement mortar Nail
Optional ridge Ridge exposure 16"
closure

Ridge
Cement mortar Hip
Optional ridge
closure
16" gable exposure
26 nailer
Field
16"
m 12 wooden strip
16" 483m or birdstop
m
406m
Gable (L) Gable (R)
Felt
Cement mortar
Ridge detail

Metal channel flashing

Tile

1"(25mm)
Birdstop
Felt
Flashing detail Optional 23
at wall nailer
Nail
12" 12" Tile
305mm 305mm
Metal
edge
Birdstop
23 nailer
22 nailer Felt
23 nailer
22 nailer
Gable detail
F I G U R E 1 0 - 1 0 Installation details for eaves, ridges, gables.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 336

336 CHAPTER TEN

Counterflashing
Flashing
Flashing
Metal channel flashing
Cement mortar Tile
Tile
Felt

1"(25mm)
Felt
Flashing detail at wall

Ridge exposure 16"

Ridge

Cement mortar
Optional ridge closure
6" gable exposure
Field
19"
m 12 wooden strip
16" 483m
m or birdstop
406m
Gable (L) Gable (R)

Felt
3"
m
Cement mortar
76m
Ridge detail

Flashing
Cement mortar Booster
Booster

Birdstop Felt
Felt 23 nailer
22 nailer
Flashing detail at wall
Gable detail
Booster 131/2"(343mm) 131/2"(343mm) 131/2"(343mm) Booster
tile 6" Birdstop tile
31/4"
152mm 83mm

Felt 10"254mm 10"254mm

Felt
23 nailer 23 nailer
Gable (L) 22 nailer 22 nailer Gable (R)

Spacing detail

F I G U R E 1 0 - 1 1 Laying barrel/mission tile on roof.

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CLAY AND CONCRETE TILES

337
Oriental Style: Figure 10-12 shows a typical oriental roll-style tile lay-
out and installation details. Without the use of ornaments, this tile is
used in western contemporary designs. While the most traditional
color for a Japanese-style tea house or temple is black, these oriental-
style tiles are available in natural red and glazed colors.

Turret Tile
True turret roof designs or fan-shaped applications are now possible
without compromising design concepts. To determine the quantity of
tile needed and specific installation guidelines for a given job, ask the
manufacturer to provide a scale drawing or blueprint of the top and
side views. All that the manufacturer needs is the diameter of the cir-
cle and roof pitch (Fig. 10-13).
The following are general instructions for installing turret tiles.

■ At the first course, between vertical chalklines, install a clay

birdstop and then place the pan tile on top of the vertical chalk-
line.
■ Fasten each pan tile with a copper or other noncorrosive
11-gauge, large-headed nail, or use the wire-tie system.
■ If the job site is located in a high-wind area, use mortar or other
sealant to secure the pan tile.
■ Once the birdstop and pan tiles are in place, install the booster
and starter tile. Secure with copper wire or noncorrosive nails.
■ For the rest of the courses, lay 16 inches to the weather. When
the tile becomes crowded, adjust to the next smaller size and
continue to the top of the roof.
■ Follow the chalkline and use the turret worksheet provided by
the manufacturer.

Prior to installing the last two or three courses, lay a mockup to

assure proper fit. Do not use adhesives or nails to secure the tiles until
the mockup is complete and satisfactory. Note that the final two or
three courses normally lose one to two lines, or more, close to the top.
Start installing the final two or three courses from the top down and
secure each tile.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 338

338 CHAPTER TEN

Field tile 12 battens

Eave tile
Felt
22 eave strip
Flashing 91 /2"
m
9" 241m
m
Side detail 9" 228m
m
3" 2 8m
2 71/4"
m Ridge
76m 26 nailer 184mm
1
Cement mortar 266 2"
mm
Ridge field (optional)
Field
3 /4"
m
Field 19m #30 felt
12 wood strip
Plywood sheathing
2"
Ridge detail 91 / m
4 1 m
2
Field Two forked ridge
Ridge field (optional) Three forked ridge
Ridge Ridge down end
Ridge end
Ridge starter (with joint) Ridge
Gabler corner (right) (outlet Ridge starter
width 1/2"
Gable Cement 10
73/4")
(right) Gable mortar 266mm
(left) Gabler Eave Forked
corner eave
Ridge end
(left)
Field tile
Gable (R)
Gable (L)
Right gable
corner
Left gable Eave tile
24 Ga. galv. metal plaster 2"(51mm) corner
stop and flashing 24 Ga. galv. metal plaster
stop and flashing
16 nailer 16 nailer
24 Ga. galv. metal pan flashing 24 Ga. galv. metal pan
flashing
Flashing
detail
at wall 8" 8"
#30 felt 203mm 203mm #30 felt
Plywood sheathing Plywood
3"(76mm) sheathing
7" 101/2" 101/2" 10"
178mm 266mm 266mm 254mm
End detail

Field tile
Gable (L) 11/2"(38mm) Felt Gable (R)
overlap size
F I G U R E 1 0 - 1 2 Typical oriental roll-style tile layout and installation details.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 339

CLAY AND CONCRETE TILES

339

Specified
ance roofing pitch
e dist (/12)
Slop

Diameter
Side view

Felt
Top of
turret

Eave circumference
vertical chalkline

Specified dimension
on center at eave
3" overhang

Cement mortar or
metal flashing cap
Starter tile
Booster tile Birdstop

Pan tile
Specified dimension
Felt on center at eave
F I G U R E 1 0 - 1 3 Turret tile diameter of the circle and roof pitch.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 340

340 CHAPTER TEN

After any style clay or concrete tile roof is laid completely, do not
allow traffic on the roof that might vibrate the framing or roof sheeting.
At least 24 hours are needed to ensure a proper set. Prohibit roof traf-
fic for at least 72 hours.

Installing Low-Slope, Mortar-Set Roofs

Roofing tiles have been installed in mortar for centuries. The prac-
tice of installing tiles with mortar over a built-up subroof evolved in
high-wind and high-moisture areas of the southeastern United
States. In this system, the built-up subroof provides the moisture
barrier and the tiles, in addition to being aesthetically pleasing, pro-
tect the subroof from the sun’s ultraviolet (UV) rays, high winds, and
external damage. The system also allows the use of tile on lower-
sloped roofs.
Apply the mortar over a solid sheathing of at least 5⁄8-inch plywood
or 1-inch tongue and groove and mechanically fasten one layer of at
least 30-pound organic felt underlayment to the sheathing. After
applying the first layer, install metal eave flashings. Next, apply one
layer of mineral-surfaced rolled roofing material to the underlayment
with hot steep asphalt or mastic and then backnail. Other mineral-sur-
faced products can be used, such as MBR, although care should be
taken to guard against roof slippage.
Mortared tile can be used on slopes a minimum of 2 inches in 12.
On slopes between 5 inches in 12 and 7 inches in 12, additional
mechanical fastening is required for the first three courses in areas
subject to high winds. On slopes 7 inches in 12 and steeper, mechan-
ically fasten all tiles. Mortar used to adhere tile to the subroof
should be as specified in ASTM Specification C-270 Type M. Soak-
ing the tile prior to installation, adding additives to the mortar, or
both, might be required to achieve proper adhesion between mortar
and tile.
In areas of the country subject to blowing sand or heavy rainfall,
use mortar at ridge or hip intersections to provide a weatherblock. Use
mortar sparingly and only to provide proper bedding for hip or ridge
tiles. Specially designed metal weatherblocks are available from most
manufacturers.
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CLAY AND CONCRETE TILES

341
Reroofing Tile Roofs
Roofing contractors, architects, and specifiers, particularly those in the
Sunbelt or Western states, sometimes encounter a reroofing project
that involves a clay tile roof that is 70 years old or more. Their first
impulse might be to draw up specifications for the job on the assump-
tion that the existing tile needs to be entirely removed and replaced
with new material. This thinking is understandable. UV radiation,
heat, moisture, and exposure to the elements work together to limit the
life span of most roofing materials to 25 years or less.
But first-quality clay roofing tiles are different. They last indefi-
nitely if the roof is properly laid and maintained. There are many
examples of old roofs that remain basically sound, with the clay tile
intact and the underlayment in generally good repair. When these
roofs begin to leak, it is often a result of problems with the underlay-
ment. The tile often can be used again.
Failure to understand the long-lasting nature of the best clay tiles
could be a costly mistake. A simple computation based on the money
saved in new materials, plus the life-cycle cost benefits offered by tile
roofing, normally results in a reroofing specification based on lifting and
relaying the existing tile. Even if the existing tile is in good condition
overall, however, there can be broken or damaged tiles on the roof.
The first step in assessing the condition of the roof can be conducted
from the ground. Using a predetermined test area, count the number of
broken or damaged tiles to get a percentage of probable breakage. The
survey can be done with binoculars, and normally provides a reliable,
rough estimate of how many tiles need to be replaced.
Deterioration in clay roofing tile is easy to spot. It is almost invari-
ably the result of water absorption in tiles that were not manufactured
properly. Most roofing tile failures can be traced to the use of inade-
quate raw materials or lack of proper time and care in the production
process. The inferior tiles that result have a tendency to absorb mois-
ture. The moisture then expands and contracts in response to the
extremes of the freeze and thaw cycle in the north and to heating by
the sun in warmer climates. This process causes the tile body to flake
and spall.
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342 CHAPTER TEN

The first sign of trouble is usually small chips of tile in gutters or

around the foundation. Areas of discoloration, visible from a distance,
might indicate that the internal body of the tile, which is lighter in
color, is showing because the surface has chipped or flaked. The tile
might appear fuzzy at the edges, and the shapes might be unclear. A
closer inspection on the roof itself might reveal a crazed pattern of
cracks in individual tile bodies. If such problems with spalling, crack-
ing, etc., are widespread, the tile may in fact be deteriorated and in
need of replacement.
With luck, the buildings’s owner made the decision decades ago to
use a tile designed to last the lifetime of the structure and damage is
limited to isolated cases of broken or detached tiles. If there is any
doubt, take representative samples and send them out to a reputable
tile manufacturer who offers a testing service. The tests look at the
major factors in tile condition: pore structure, compressive strength,
and water absorption rates. Good results on these tests indicate that
the tile is a strong candidate for additional decades of useful life.
Contractors reviewing the specifications for a job involving the
removal and relaying of a tile roof may not be completely familiar
with the procedure. There are many questions that should be
answered before they go forward with a bid based on this approach.
These questions can be answered by the tile manufacturer or the local
representative.
An experienced roofer working from the manufacturer’s installa-
tion manual normally has no more difficulty laying a tile roof than a
shingle one. The major difference between the two is that tile is a fired
material. It must be cut using special tools and is subject to breakage.
More care is required when handling tiles.
When lifting and relaying tile roofs, weight can be a concern. If ade-
quate scaffolding is available, or if the structure is deemed strong
enough, the tiles can be lifted in sections and stacked near the work
area. Common sense and experience are normally enough to let the
roofer know whether this kind of loading might cause movement or
possible collapse. When any doubt exists, consult with an engineer. If
the roof or scaffolding is not strong enough, move the tile to the ground
via a conveyor belt and develop a plan for restocking the roof with tile
as needed.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 343

CLAY AND CONCRETE TILES

343
The actual removal of existing tile is extremely easy. The tile is sim-
ply lifted and rotated, which normally pries out the nail. After the
underlayment and deck are deemed satisfactory, the tiles can be relaid
in the same manner as new tiles.

Installing Fiber Cement Shakes

A relative newcomer to concrete roofing is the fiber cement shake.
This roofing product has the natural texture and tones of real cedar
shakes with the added benefit of a Class A fire rating. Shakes resist the
damaging effects of sun, water, humidity, rot, fungus, and termites.
They contain no asbestos, formaldehyde, or resins.
For roof pitches 4/12 and greater, cement slates and shakes can be
installed over spaced or solid sheathing (Fig. 10-14). Install 18-inch-
wide, 30-pound underlayment, the starter course at a 9-inch exposure,
and then succeeding field courses at a typical 10-inch exposure. Lap
the underlayment over the ridge and hip to create a double layer.
For a 1-inch stagger, use a 9-inch underlayment exposure. Some
regions require application over
solid sheathing. Contact the local
building department for sheath-
ing code requirements.
For roof pitches 3/12 and less
than 4/12, lay shingles over solid
sheathing. For 4/12 and greater
pitches, install a 36-inch, 15-
pound underlayment described
previously. For roof pitches under
3/12, install for appearance only
over an approved sealed-mem-
brane, low-slope roof system. Spaced
sheathing
In snow areas, an approved 36- 18" interlayment
between
inch snow-and-ice moisture bar- courses
rier is recommended at the eave.
Cant strip
To lay fiber-cement shingles
F I G U R E 1 0 - 1 4 Installing cement slate
follow these steps. (See also Fig. and shakes over spaced or solid sheathing
10-15.) on roofs with pitch of 4/12 and greater.
Scharff_Chap10_6x9-GOOD 9/21/00 11:24 AM Page 344

344 CHAPTER TEN

✓ Item
1
Install a ⁄4-inch cant strip flush along the eave over the
interlayment and beneath the starter course.
Install the starter course face down, with up to 11⁄2
inches overhang at eave and 11⁄2 to 2 inches at rake.
Fasten the starter course with 13⁄4-inch corrosion-resist-
ant nails, staples, or screws, located within 1 inch of the
eave line.
Interlap field shakes with interlayment to create an
approximate 2-inch headlap and a typical 10-inch
exposure to the weather.
Install shakes with an approximate 1⁄2-inch keyway and
11⁄2-inch minimum sidelap. Applications with more
narrow keyways require additional material, which
changes the appearance of the roof.
Alternate the sequence of shake widths every third to
fifth course to avoid a stair-step pattern.
Fasten the field shakes with either two 16-gauge,
7
⁄16-inch crown, 13⁄4-inch galvanized staples, or 13-gauge
nails or screws. Locate the fasteners approximately 101⁄2
to 111⁄2 inches above the butt, and 1 inch in from each
side of the shake.
Do not walk on the smooth surface of installed field
shakes.

F I G U R E 1 0 - 1 5 Installing fiber cement shingles.

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CLAY AND CONCRETE TILES

345
1
■ Install a ⁄4-inch cant strip flush along the eave over the interlay-
ment and beneath the starter course.
1
■ Install the starter course face down, with up to 1 ⁄2 inches over-
1
hang at eave and 1 ⁄2 to 2 inches at rake.
3
■ Fasten the starter course with 1 ⁄4-inch corrosion-resistant nails,
staples, or screws, located within 1 inch of the eave line.
■ Interlap field shakes with interlayment to create an approximate
2-inch headlap and a typical 10-inch exposure to the weather.
1
■ Install shakes with an approximate ⁄2-inch keyway and
1
1 ⁄2-inch minimum sidelap. Applications with more narrow key-
ways require additional material, which changes the appearance
of the roof.
■ Alternate the sequence of shake widths every third to fifth
course to avoid a stair-step pattern.
7
■ Fasten the field shakes with either two 16-gauge, ⁄16-inch crown,
3
1 ⁄4-inch galvanized staples, or 13-gauge nails or screws. Locate
the fasteners approximately 101⁄2 to 111⁄2 inches above the butt,
and 1 inch in from each side of the shake.
■ Fasteners must penetrate through the tail of the shake beneath
and 3⁄4 inch of the sheathing or its full thickness, whichever is
less.
■ Do not walk on the smooth surface of installed field shakes.

The treatment at ridge and hip and in the valleys and the flashing
at chimneys, vents, and so on, are handled in the same manner as that
described for wooden shakes and slate in Chaps. 8 and 9.
Cement fiber shakes usually can be applied over one existing com-
position or wooden-shingle roof system, if the existing roof is rela-
tively smooth and uniform. Wind-resistance performance applies only
if fasteners penetrate the sheathing as specified. Structural evaluation
and local building code approval is required. Longer fasteners are
required.