The best way to avoid unnecessary costs related to roof replacement or repairs is to know your stuff. Do as much research as you can. Salespeople tend to have a vested interest in making a sale. Roofing materials come with pro-rated warranties. A homeowner can find out what the material is and then the life expectancy for that product. If you are already beyond the life expectancy, then you need to start thinking about replacing the entire roof. However, if you have only got ten years out of materials that are rated for 20 years (for example), then you need to question whether your roof needs to be replaced and if it does whether a manufacturer’s warranty would cover part of the material costs.
For a traditional asphalt shingle roof, you can determine this often for yourself. Flat roofs using torch-on membrane systems or the old tar and gravel method are usually more difficult to assess, so you might want to employ some form of independent inspection not employed directly by a roofing company. With asphalt shingle roofs the key thing to look for is where the surface granules on the shingle are worn away, and you can see the black underlay. If the colored surface material is worn away over most of your house, you are going to have to re-roof soon.
Moss may also create and hide a problem. Moss should not be allowed to develop, but if it has it may destroy the surface of asphalt shingle prematurely especially when trees shade a house or roof sections are facing north in colder climates. Gently try removing the moss with a broom and once again if the shingles underneath the moss have lost much of their surface granules they will need replacing. Avoid power washing your roof. It may make the roof look better initially however you are aging your roof several years in one go, and hastening the date it will leak.
To stop moss from growing to buy a zinc strip (moss strip) from your local building supply yard in the roofing section. This is a 3-inch wide strip of metal that looks like pliable tin and is rolled the length of the roof along the ridge and has one edge tucked just under the ridge caps. Precipitation collects zinc in it as it runs over the metal, and as this water runs down the roof, it kills off the moss before it becomes a problem.