Most common leak areas on your roof

Having a leak in your roof can be more than a nuisance. Leaks are the cause of major issues such as structural damage, mold, dry rot, and interior damage, and more. Locating a leak can be really easy or really hard depending on the roof area and weather conditions.

Most roof systems function by the principal of gravity. Understanding the way water runs down your roof can be a big help in locating a leak source. At Ace Roofing we like to approach a leak diagnosis by thinking like a raindrop. However, sometimes the horizontal sheeting can cause the water to run sideways and become misleading to the true leak area. Common leak areas we check first are:

The field of the roof

This area is less common than other leak areas and is usually found on older roofs. Usually asphalt is very resistant to field leaks. Other roof systems such as tile, slate, and wood shake are more delicate for foot traffic so having an experienced Ace Roofing professional perform an inspection my be a better option than walking around on yourself.


These are high risk areas of your roof because they are the areas that experience the most water movement. A valley is the connection line between two faces of the roof that meet. Depending on the age of your roof, roof system type, and the city code guidelines; metal or rolled roofing should under lay the valleys of your roof. Sometimes there is nothing under laying the valley. issues occur from rust on metal valleys or poor and faulty installation.

Head wall and step flashing

These are areas where the roof meets a wall. On a wall that is going down along a slope, there are overlaying pieces for every row of roofing called step flashing. Leaks happen in these areas more common than other areas.  This flashing may be behind wood siding or in front of a brick wall. The flashing should extend over the shingles at least three inches. If the wall is brick or other masonry, the flashing must bend and extend one inch into a mortar joint. Tar, caulk or roofing cement should never be used in conjunction with these materials. If you see them, it is a sign that someone tried to patch a leak


These are the source of many, many leaks. Chimneys contain four different types of flashing. All must be right or you will have a leak. Plus, the counterflashing that goes into the brick mortar joint must be right. A hairline crack above the flashing can allow vast amounts of water to run behind the flashings.

Plumbing Vent Flashings

Newer vent flashings are a concern of mine. Many of these incorporate a rubber seal with an aluminum flashing. The rubber can fail in as little as 10 to 15 years. Look for cracked rubber around the plumbing pipe. The flashing should dive up and under the shingles that extend up roof from the middle of the plumbing vent. The bottom half of the flashing should be exposed and actually cover the shingles.

Furnace or B-Vent Flashing

These flashings are basically identical to plumbing vent flashings. However, they sometimes have a metal storm collar. These simply fit tightly around the vertical pipe that exits the roof. If they become loose, the storm collars can cause leaks. Rusting on the stack can also be responsible for leaking

Ice Dam Leaks

Ice dam leaks plague people in the snow belt. These leaks can happen even if everything on your roof is just fine! Ice dams block the natural flow of water down a roof. The water begins to back up under flashings, shingles, tar paper, etc. Once water begins to flow into the house, it can drip for days. The only means of prevention is to install membranes under the roofing. The membranes won’t stop the ice but will stop water leaks if installed properly.

Wind Blown Rain Leaks

Wind driven rain can also be a major problem. Once again, you could actually have a good roof and wind will drive water up and under your roofing materials. The only lines of defense are felt paper and the ice dam membranes.

Roofing cement under shingles on the edges of roofs that face the wind are also a good idea. Don’t underestimate the power of a 70 mph sustained wind-driven rain.

Non-Roof Leaks !

Sometimes you think you have a roof leak when in fact the roof is fine. Attic condensation is a prime example. High humidity can cause condensation and “rain” to fall in your attic. It can also make the underside of the roof sheathing look wet. You think you have a leak instead. The key to this is having proper ventilation.

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