A leak from one dislodged tile is a small and inexpensive matter, but if you do not inspect your roof regularly, this will go unnoticed. By the time that you DO notice it, it may be because water is dripping into your spare room! This means that this whole area of the roof structure is soaked, the ceiling will need to be replaced and hopefully the flooring will recover.
Always check your roof after a wind storm, as most roofing is not designed to withstand fierce winds. Scrutinize the tiles for cracks, splits and torn-off corners; also check for lifting. Lifting is a common cause of roof leaks, and can be easily rectified. Be aware of multiple tiles lifting, as this could be a sign that the roofing material is too old and is warping from all the weathering.
Climb into your attic/loft and ensure that any insulation that you have in your roof is not right up against the roof itself. There has to be a gap for air to circulate; also when a roof heats up and there is insulation directly behind it, this heat is thrown back into the roofing and excessive heating like this can damage and warp the roof.
Another weakness in all roofs is the flashing. Flashing is designed to provide a watertight junction between roof materials and structure, especially if the roof projects out or changes design (as with extension roofs). If you are installing a new roof, it is worthwhile to get the flashing 'inspected' as it is a common failure area.
Often the simple fact that the gutters, leading into down pipes from the roof, are blocked with leaves and twigs can cause a problem. Roofs must have adequate run off, especially in the areas which may have snow. Water trapped in the gutter will mean that it will back up the roof for a few inches and have time to seep into the edges of the roofing tiles. Not all homes have adequate perimeter protection on their roofs, although this is one good feature to ask for on a new roof.
Quite often homes incur roof leaks all at the same time (often after strong gales winds and torrential rain etc). This can mean that all contractors are busy and you have 'stop up the leak' until you can get help.
If you do get a leak, and you have placed buckets under the dripping water, be aware that the leak may be in a completely different place than it would seem. Locating the source is difficult, as water can run along horizontal timbers and appear to be leaking from a place that is sound. Getting up into the attic and actually looking for a wet spot on the roof decking will be an accurate way to tell.
If you can find the spot an emergency patch can be made applying roofing felt and using plastic cement to hold it until you can call in a contractor. You can also attempt to repair it yourself, if it is just a shingle that is damaged. You can carefully prize up the roof shingle by removing the three or four nails that are holding it in place; next, apply a generous coating of tar beneath the tear in question, and also coat the underside of the shingle with a with a coat of tar before putting it back in place. Add a spot of tar to each nail head. Most roofing companies advise against the 'liquid' asphalt repair products.
Roofs can also be temporarily repaired using roof membrane and sealants. Care must be taken to clean the roof surface first to ensure that the sealant will stick and keep the leak protected from rain etc. In fact, as long as the roof is clean and dry, the wonder of the 20th. Century - duct tape - can also be stuck onto the roof!
