As a flipper, you will need to be able inspect a property's roof and determine if it's in acceptable condition, or needs to be repaired or completely replaced.
The following are the most common warning signs that you need to repair or replace your roof.
Sign #1: Roof Age
Typically, you will be able to find out the roof age from the seller's disclosure. Most roof's will last between 15 to 25 years, but it can depend on the type of roof and your local climate.
Generally speaking, if the roof is approaching 15 years of age, you will need to further evaluate the roof condition & may want to seriously consider replacing the roof. If you are looking at a house that was built in the last 15 to 25 years, it's probably safe to assume that the property needs a new roof in the near future.
Sign #2: Faded Shingles Or Discoloration
Shingles lose their color over time due to prolonged sun exposure. If the roof appears to be faded or discolored that is generally a sign of an older roof that may need to be replaced.
Sign #3: Shingle Curling
Shingles that are curling or buckling are likely another sign that you may need to replace the roof. Curling or buckling is typically caused by poor ventilation in the attic which traps heat & moisture in the attic. Usually once a shingle starts to curl or buckle, it's time to start considering a new roof.
Sign #4: Granular Shedding
Granular shedding is also another sign that the roof shingles are deteriorating. Inspect the gutters to see if you find little black granules which have fallen off of the asphalt shingles.
If you find granulars in your gutters, this could have been caused by hail, a critter, tree debris/limbs, or it could mean your roof is approaching it's useful life and needs to be replaced.
Sign #5: Missing Or Broken Shingles
Missing shingles should be a fairly obvious visual sign that your roof has been damaged in a storm or has deteriorated to the point of no return.
If the missing shingles were caused by a recent storm, you may be lucky and only need to repair the missing shingles.
Sign #6: Multiple Layers Of Roofing
Some homeowners or even rehabbers may have tried to cut costs on re-roofs and installed a new layer of roofing over the old layer of roofing.
Some insurance companies won't insure homes with multiple layers of roofing and in many cases multiple layers can invalidate the roof warranty.
Sign #7: Water Stains On Ceilings
Water stains on interior ceilings is an obvious sign that your roof is failing to keep water out of the home and will likely need to be repaired or replaced.
Note: If the roof looks new, it could be that the previous home owner replaced the roof, but did not fix the water stain on the ceiling.
Sign #8: Daylight In The Attic
If you go in the attic and can see daylight shining through the roof sheathing and roof shingles, then you will need to repair or replace the roof. If light can get in, then water can get in!
Architectural / Aesthetic Reasons
The previous reasons to replace a roof were purely based upon the structural integrity, but you may also want to replace the roof if it just looks plain ugly. Curb appeal is a big factor for getting potential buyers in the door, so if you have an ugly roof, you may want to consider replacing it.