Roofing With Concrete Tile - Continued

Cutting Tiles

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.

Figure 6. 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 flashing.

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 board.

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 these openings.

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

Fred Martin