Here are some questions to ask the home inspector after he or she "walks the roof":
How many layers of shingles are on the roof?
There may be a second layer (or more) of shingles under your roof that you cannot see. Most manufacturers will not warranty a second layer. And there may be bad plywood or flashing systems underneath the layers which can cause leaks. When replacing a roof, a roof with two or more layers will generally increase the price as there is more waste.
Are there any soft spots?
Soft spots in the roof are caused by plywood that is rotting. Rotting plywood is caused when too much moisture reaches it over a period of time. In simple terms, wet plywood means the roof is leaking.
How are the flashing systems?
Flashing is metal that is bent and installed in vulnerable areas to help water travel away from those areas. If the flashing is deteriorating or is installed incorrectly, the roof will leak.
How are the pipe collars?
There are pipes coming out of your roof that are used to ventilate gases in your home. Around the bottom of the pipes there are rubber boots that prevent water from getting into the home. With age these pipes can lose their seal and cause leaks and damage to your home. Repairing pipe collars is a simple fix.
What type of sheathing is there?
When looking from the attic, you can see the sheathing. This is the base of the roof. Most roofs have plywood. Some older homes may have cedar shake. The cedar shake must be removed. Cedar shake does not have any nailable surface, so putting shingles over it will cause future issues. Replacing a cedar shake roof is much more expensive that replacing a roof with plywood. Having this information upfront will prevent sticker shock when it comes time to replace the roof.
Are the shingles installed correctly?
Dimensional shingles have become more popular in the past 15 years. Before this, a majority of the roofs were done with three tab shingles. When the most popular choice of shingles changed from three tab to dimensional, some roofers did not realize that the proper installation procedure also changed. The improperly installed shingles will cause leaks around the 10-15 year mark. This is fairly common and is difficult to spot.
If your home inspector does not walk the roof or has any trouble at all answering these questions, contact a licensed roofer and ask for a roof inspection.