The protection afforded by your roof can be compromised by various things that fall into three main categories: weather-related, structural, and natural. Within these categories, you can find the 10 main causes of leaky roofs and therefore help protect your roof from expensive repair needs or replacement.

Weather-Related

Rain
Any moisture can damage a roof and cause it to leak over time, which is why rain is the number-one cause of leaky roofs. A pristine roof allows rainwater to flow into the gutters and down away from the structure, but the smallest chink or crack can introduce water underneath the shingles and affect the wooden structure of the house. This leads to rot and mold that can even affect the interior, both aesthetically and structurally.

Snow and Ice
Just as rain flows into small cracks, melting snow can do the same. However, with low temperatures, this flow can refreeze over a period of days, expanding crevices and causing more damage over time. Also, ice can block gutters, so water from the melt backs up and sits on the roof for a longer period of time. One of the first problems that can occur with the snow and ice situation is that the gutters and downspouts can fill with ice and tear away from the building.

Wind
Windstorms cause excessive damage to roofs by physically ripping off shingles and by lifting up sections of shingles or other structural materials and either blowing them away or allowing rain or other debris to be introduced underneath. Even periods of moderate wind can contribute to this problem that causes leaky roofs down the road.

Moisture Buildup
Any of the weather-related events such as rain or snow that contribute to leaky roofs can also cause condensation to build up in the attic, the insulation under the roof, or the wooden parts of the room itself. This leads to leaking as the condensation becomes greater and begins to drip and run. A well-ventilated attic can help alleviate this concern.

Sun
Although not a quick or dramatic process like shingles being torn off in the wind or an ice jam causing a leak, the continuous beating of the sun onto the roof will cause deterioration in the long run that can result in a leaky roof.

Structural

Damaged Shingles
No matter what the reason, anytime a shingle is damaged or torn off, the roof loses its structural integrity and may leak. Regular inspection of the roof is important to make sure you can replace the shingles promptly if this occurs.

Old and Worn-Out Shingles
There is a reason why roofs need to be replaced after a certain number of years. As the shingles age they can naturally crack, curl, or shift, creating spaces in the roof where leaks can occur.

Damage or Deterioration to the Flashing
The material that surrounds chimneys, skylights, attic vents, and any other junction where shingles meet another material are a common area of leaking roofs. These should be checked regularly.

Natural

Tree Limbs and Branches
The overhanging limbs and branches of nearby trees can damage the shingles if they rub against them as the wind blows. This can create gouges that weaken the integrity of the roof overall. Also, storms can make branches fall off of trees and cause more acute damage.

Algae, Moss and Mildew
The growth of any of these plants or fungi on the roof itself cannot only create an unsightly situation with discolored boards and shingles, but can also contribute to quicker deterioration due to rot and mold. These can grow especially where the roof is shaded or frequently moist due to overhanging branches, or where there is a buildup of debris such as fallen leaves that can trap the moisture close to the roof.