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Last edited 08 Mar 2021
A single location, leaking for the first time, usually is not significant enough to prompt a full replacement. More likely that not, a single component of the roofing system (flashing, vent or a mis-nailed shingle) has failed, but the rest of the roof still could be in decent condition.
Leaks in multiple locations bode more ominous results. If multiple locations are having shingles loosen, nails rise or flashing fail, the chance of the roof being worn out are higher. When the same location has leaked and been repaired repeatedly, the same mistaken repair may be continuing to be performed.
Next, look at the roof leak location. Is it below, or in somewhat of a direct path below a skylight, vent, or pipe? Is it possibly at a valley or roof intersection where either one section of roof meets another or where the roof meets a wall? Or rather is it out in the middle of the roof field?
Remember, there are very few leaks that are un-repairable. The issue becomes whether the roof has adequate remaining life to justify the repair's cost. However, leaks in the middle of a roof field with no nearby intrusions into the roof can be a bad sign.
If an unsightly roof (fungus or mildew stains or moss growth) is motivating the need for a new roof, it's important to find out more about what is under the stains or moss. A dirty roof does not always require replacement.
There are some roofs that will not withstand even the gentlest cleaning without sustaining damage. For example, there are some moss types and infestations that cannot be properly dislodged without stressing a roof. If a roof is on the borderline to start with, such a roof is best left alone. Money will be better spent on a new roof.
Aside from excessive moss infestations, cleaning the roof will most often help maintain roof life, specifically where growths such as moss could cause "micro-dams" on the roof and result in damage. Always be sure that the roof has adequate life remaining so maintenance will not be wasted.
If the roof's shingles are starting to cup or curl upward, it may be time to consider replacing them. Cupping and curling are often signs of interior ventilation issues that result in excessive attic temperatures. It is a problem that could be corrected with a new roof installation as well, because it takes life off a roof that otherwise might have lasted longer.
Loose or dislodged shingles may signal an unfortunate, premature death of a roof. This may be a sign that the roofing material was installed incorrectly, even if the material itself has more life remaining.
Similar to leaks, the number of trouble spots will reveal a great deal. If there is only one trouble spot, repair should be sufficient. Multiple locations, however, indicate a bad installation that may justify replacement.
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