If several tiles are damaged over a relatively small area of the roof, it is probably just as easy to re-tile that area than attempt to replace tiles individually. Buy enough tiles to do the job with a few spares in case you break any.
Always stack the tiles out of the way, since they are easily broken and always carry them on edge rather than flat on top of each other — that way they are less likely to break under the weight.
As with renewing an area of slates, you must recreate the original overlapping pattern of the tiles to ensure that the roof retains its strength and is also waterproof.
Unlike slates, you cannot cut tiles to size, so you must make sure you get the right number of special tiles for finishing off courses at gable ends and for making up the eaves course. You will also need a supply of 11/4in copper, zinc or aluminum roofing nails for fixing the tiles to the battens. If the tiles are of the interlocking type held to the battens by clips and nails, you must buy sufficient clips as well.
Wooden wedges, as described opposite, will be needed for lifting the tiles surrounding the repair so that the old tiles can be lifted from underneath them and the new ones hooked in place.
Begin at the top of the damaged area, working downwards and removing tiles as described opposite. Once you have removed a few from the upper courses, you will expose those below so that you can simply lift them off. If they are nailed down, cut off the nail heads with pincers.
The tiles will be heavy and brittle, so handle them with care and lower them to the ground with a bucket and rope. Keep perfectly good tiles for re-use.
Once the tiles have been removed you can inspect the roof structure below. This will comprise the tile battens and, in most cases, below them a layer of roofing felt. Brush off any dirt and dust and pull any remaining nails from the battens with pincers.
Begin fitting the new tiles along the bottom of the repair area, working your way up the roof. Hook the nibs of the tiles over the battens and nail every third or fourth course down for extra security.
As you work, use the wooden wedges to lift the surrounding tiles so that those below can be lifted into place. Make sure any interlocking types are properly linked together and if these are normally held to the battens with clips and nails, fit these to every course.
Continue to the last tile, fitting it in the same way as described opposite. If retaining clips are used on the tiles you will not be able to fit a clip to the last tile, but the weight of its neighbours will hold it down.
Gaps between the overlapping tiles at the edges of the roof should be pointed with mortar. First coat the edges of the tiles with a bonding agent and then mix some more into the mortar before you use it.