Roofing With Concrete Tile - Continued
Concrete tiles are cut with a diamond blade, using either a
portable circular saw or a gasoline-powered cut-off saw (Figure
6). If only a small corner needs to be trimmed and the cut area
will be covered with flashing or a trim tile, it is often
easier to knock off the corner with a hatchet than to cut it
with a saw.
A small corner of tile can often be knocked off with a
hatchet (left). Larger cuts are made with a saw
equipped with a diamond blade (right).
The concrete dust from a saw should be removed with a leaf
blower, not left on the roof (Figure 7). Otherwise, the dust
will mix with rain or dew, creating a hardened concrete paste
that discolors the roof.
Figure 7. Cutting tiles on
the roof leaves fine cement dust, which should be
thoroughly removed with a leaf blower. If the dust is
left on the roof, it can turn into an unsightly cement
paste when it rains.
Plumbing vents. Concrete
tiles are notched around plumbing vents, which get primary
flashing when the asphalt felt is installed. The secondary pipe
flashing is either aluminum or galvanized steel, depending on
the tile profile, and is installed when the tiles are nailed.
Aluminum is used with S-tiles, because it is soft enough to be
bent to conform to the curve of the tiles. Metal chimneys, like
plumbing vents, get both a primary and a secondary
Valleys. The fastest way to
complete a valley is to finish installing the large cut tiles
while omitting the small triangular pieces closest to the
valley. Once all the courses up the valley have been installed,
we go back and insert the small triangular pieces (the last
piece in each course, where the course intersects the valley).
These are installed with a dab of roofing cement.
All of the valley tiles should run a little long. Once they
are all installed, we snap a line along the valley and cut the
tiles in place with the cut-off saw (Figure 8). These cuts must
be made carefully, so as not to nick the valley flashing.
Figure 8. Where tiles
intersect a valley, they are cut roughly, so they run a
little long. Then a chalk line is snapped, and the
tiles are trimmed with a saw.
Rakes. Rake details
differ, depending on the tile profiles being installed. The
S-tiles we use are trimmed with a simple barrel trim tile. We
secure each rake tile with two horizontal nails driven into the
rake board (Figure 9).
Figure 9. Rakes are
trimmed with barrel tiles. Each tile is secured with
two nails, which are driven horizontally into the rake
Hips and ridges. Once all
of the field tiles are installed, it's time to trim the hips
and ridges. Each ridge tile is installed with a single nail
into the ridge board. On the top of the nailed end of each
ridge shingle, we lay down a bead of asphalt roofing cement to
secure the unnailed end of the next ridge tile (Figure 10).
Figure 10. This style of
ridge tile is used to trim roofs with flat tiles. Each
ridge tile is secured at one end with a single nail and
at the other end with asphalt felt.
The last step is to install mortar to fill the gaps between
the top course of field tiles and the ridge and hip tiles. We
use a simple mortar mix — 1 part Portland cement to 3
parts sand. As an alternative to using mortar, some
manufacturers offer an accessory ridge closure trim to seal
Walking on Concrete Tiles
If you're not careful, walking on installed roof tiles can
break them. Concrete tiles are weakest when they are fresh from
the factory, or "green"; they get stronger as they age. The
best spot to place your foot is at the 3-inch-wide head lap,
where the bottom of one tile is supported by the top of the
tile on the course below. With S-tiles, it's also best to place
your foot so it spans the tops of two tiles.
Even with care, it isn't unusual to break a tile after it has
been installed. Luckily, replacing a broken tile isn't
difficult. Gently lift the tile in the course above the broken
tile (since the tiles are secured with a single nail, this is
usually fairly easy). Scoot the tile to one side as much as
possible. Wiggle the broken tile to remove it, or break it if
necessary. Be sure to pull out the nail, and patch the nail
hole with roofing cement. Then slide in a new tile, along with
a dab of roofing cement to secure it
is the owner of Martin Roofing, a 53-year-old roofing company
in San Diego, Calif., and is a past president of the San Diego
Roofing Contractors Association.