What to look for?
Roofing shingles condition
Improper nail penetrations
Proper roof covering and underlayment installation
Valley flashings conditions
Vent stacks and roof penetrations
Structure or any sagging or bulging areas
Average life expectancy of different roofing materials
Asphalt shingles - 20-25 years
Wood shake/shingles - around 30-35 years
Tile roofing - 50+ years
Metal roofing - 40-70 years
Flat roofing membrane - 10-20 years
Of course these numbers are based on proper maintenance, climate conditions, and other elements of your home that come into play, such has proper attic ventilation. Attic ventilation helps keep your roof system cooler, without it your roof's life will overheat and be shortened. Climate and weather conditions such as snow, hail, hurricanes, wind, and tornadoes can obviously shorten the lifespan of any roof. You should always inspect your roof annually and after any storm or harsh weather.
Roof shingle condition
A few signs that your roof as reached its life span are missing granules/grit or excessive amounts of granules in your gutters, missing/damaged shingles, or if shingles have started curling, buckling, or torn. You want to always check after any big storms if any sections of shingles are missing. Granules are a significant part of roof shingles. The granules give the shingles its ability to shed water, which is what the roof is for. They also provide UV resistance, the sun is your roofs number one enemy.
Purpose of drip edge flashing
Proper drip edge flashing is important for proper drainage protect to roof and structure of the home. Water is shed off of your roofing system to this area where it falls to the ground or gutters. This non-corrosive flashing will extend the life of your fascia and prevent wood rot.
Nail penetrations and exposed nails
Exposed nails that are not sealed/caulked-exposing nails-is an easy entry point for water to leak into the home and cause further damage and damage the roof sheathing/decking. It is common to find exposed nails used for vent stack or roof penetration flashings.
Vent stack and roof penetration flashings
Overtime, flashings can take some wear and tear and deteriorate. This opens up opportunities for potential leaks and can make larger dents into your wallet. It is common for people to use black roofing tar to seal these issues, but roof tar is a temporary fix that will become brittle eventually leak all over again. These boot flashing are very inexpensive to save you more money down the road. Another thing to consider is the location of these roof penetrations. Pictured here is a vent stack that in installed in one of the roof's valleys. This area receives a lot of rain water drainage and that roof penetration will be highly prone to leak.
Flat roofing conditions
There are a few different materials to choose from with flat sloped roofing. Issues to watch for over time are spots of "alligatoring", any signs that water has been ponding, and proper installation. Alligatoring happens over time from the brutal UV rays. These dark spot show signs of ponding water and with water resting in these areas, the roof will be more prone to leaking.