A good quality rood should last at least 15 to 20 years under normal circumstances, but sometimes the roof will last longer if the homeowner periodically inspects the shingles or other roof covering, as well as all the other adjoining surfaces, for potential trouble spots and signs of breakdown.
Usually only minor repairs will be needed that may postpone major repairs or replacements. This is especially true if the roof is older than 15 years and if there have been recent storms with high winds.
For maximum safety when climbing, wear sneakers or shoes with soft rubber soles, and do the job on a fairly dry day when there is little wind. If possible, have a helper stand at the base of the ladder while you are climbing so the ladder can be held to keep it from slipping when you step off onto the roof and when you climb back down when the job is done.
The ladder should be tall enough to project above the edge of the roof by at least 2 or 3 feet, so you will have something to hold onto as you climb on and off at the roof level.
Most homes with sloping roofs have some type of asphalt shingles installed, and one of the first things to look for on this type of roof is a shingle that may have been curled or bent upward during a strong wind, and may be allowing rain to be blown under it. Press it down gently to see if you can get it to lie flat. If it feels brittle or as though it may crack, heat it slightly with an infrared lamp or an electric hair dryer, or wait for a warmer day.
To keep the curled edge down, smear a liberal dab of asphalt roofing cement under the raised portion, then press it down and hold it in place for a short while by placing a brick or other weight on top of it.
If a piece of shingle is missing, or if it cracks off when you try to repair it, a fairly permanent repair can be made by using a 8-inch-wide aluminum flashing material (sold in most hardware stores and lumberyards).
Cut a piece to the size that will cover the area left exposed by the missing shingle, then coat the shingle underneath with a liberal coat of roofing cement. Slip the piece of metal in place on top of the cement (under the shingle above), then applying another layer of cement over the metal patch, pressing the shingles above down on top of it. Again, avoid using nails, but if you must, make sure the nail heads are covered with more cement.
Flat roofs, which are normally covered with roll roofing rather than shingles, should be inspected for small cracks through which water could seep. If small, these cracks can be patched by troweling on a layer of roof cement, but if the cracks are large, a patch should be made by applying heavyweight roofing felt or asphalt flashing material.
Trowel some cement over the area to be patched, then apply the patch and use galvanized roofing nails around the edges to secure it. Then spread another layer of roofing cement over the entire patch, making sure you cover all the edges and all the exposed nail heads.