It's not typically recommended that a homeowner handle their own roofing repairs, simply because the job is often more difficult and dangerous than a person may realize. A simple mistake with your repair work could actually cause more damage to the roof, and lead to eventual water leaks, softening and crumbling of the chimney, and mildew growth around shingles and tiles. If you are determined to tackle this job yourself, however, note a few common roof repair mistakes you'll want to avoid, so that your home's roof is always in good repair.
Layering the roof
In some areas, it's actually against local building codes to add new layers of roofing without removing old shingles and tiles. If it is allowable in your area, note that you may still want to avoid just adding new shingles over old ones. The added weight of those new tiles can put undue pressure on a home's framework, causing the home to shift and settle, and then leading to potential cracks in the roof, ceilings, walls, and floors of the home.
New roofing tiles and shingles also may not cover the roof's materials completely, so that torn flashing or damaged roofing paper can still allow in water, as well as heat and cold. In turn, your home is not as protected from outside elements as you think when you layer new tiles over the old.
Most roofing tiles and shingles will have some type of warranty, but this warranty usually depends on proper installation of those pieces, including how many nails, and the types of nails used, to apply each shingle. If you don't check the manufacturer's warranty and its details, you could void that warranty when making your own roofing repairs, so you cannot be reimbursed for the cost of shingles or tiles that get damaged before that warranty is expired.
Flashing is like very thin metal that is placed in various areas of the roof, to protect connections between the roof and chimney, vents, and other such pieces, and to provide added protection against water damage and leaks to the roof. If you don't replace worn and damaged flashing, the tiles and shingles you install won't protect the home from water damage. Also, this flashing needs to be installed with some overlap around its corners, to keep water flowing off the roof and away from the home. If you don't install the flashing properly when you make roof repairs, this can also mean wasted time and effort, and future water leaks.