Clay roof tile is like other roofing materials in that you occasionally have to replace loose tiles. You can replace tile roofing one piece at a time, while new asphalt shingles have to blend in with existing shingles over several courses. In most cases, it's just a matter of removing loose clay tile and replacing it. You should be able to replace tile roofing as long as you have basic carpentry skills and you're not afraid of heights.
Place your ladder so that it's not rubbing against the tile roof. Plan how you're going to replace tile roofing with a minimum of walking. Tiles are easy to break, so you don't want to take a chance on breaking more tiles as you replace the broken one. You may need to lay down padding to protect the tiles.
Remove the old tile. If it's set in mortar, chip away all of the existing mortar to make room for the new tile. Use a chisel and hammer to break the remaining pieces of clay tile for easier removal. If the clay roof tile has nails securing it in place, pull them out. It may be easier to slice a hacksaw under the roof tile and cut off the nails. Choose the method that does the least amount of damage to surrounding tiles.
Set the replacement tile loosely in position to see if it fits. If the colour doesn't match nearby courses of clay roof tile, you may have to swap out a tile from a less obvious location such as above a dormer window or a tile from the back of the house.
Mix a 1-to-3 ratio of cement and sand to make a setting mix to hold the tile if the rest of the tiles are set this way. Add only enough water to make a stiff mixture. Press the mixture on the tile and set the tile firmly in position.
Create a support for the tile from copper sheeting if this is the method of roofing used. Nail one end of the support to the roof, using a hammer. Bend the copper double to form a tab to hold the bottom of the replacement tile. Slide the top of the tile under the tile above it and set the bottom of the tile into the support.