Ten Most Common Leak Locations – A leaking roof can be a homeowner’s headache and cause water damage to ceilings and walls if the leak is not located and repaired quickly. Finding the source of a roof leak may be simple, but sometimes it can be difficult to determine where it originates because of weather conditions and the location of the leak. These tips for locating a roof leak and repairing it may help if you encounter that frustrating problem.

Diagnosing a roof leak to discover its source can be difficult because of several factors. Various weather conditions will cause a roof to leak in different areas.  Most roof coverings follow the gravitational principle, which can be helpful in finding the source of a leak.  All leaks are not that easy to find though. Horizontal roof boards can direct water up to 10 feet away and cause the wet spot on your ceiling to appear far from the actual leak source.

When it is hard to locate the source of a leak, you may need the assistance of someone watching from the inside while you spray the roof with a garden hose.  If you would rather not climb up on your roof, you should get a trustworthy roofer to help you find the source of the problem.  This can sometimes be as difficult as finding a tiny leak.  Following are some tips to assist you in locating an annoying roof leak:

An older roof may develop a leak in the expanse of shingles, shakes or slate. This area is called the roof field. Walking on an asphalt roof should not cause a problem, but you must be more careful when you walk on a slate, clay tile or concrete tile because the roofing may crack if you walk on it. Check the tops of the vertical knockouts looking for a spot with missing colored granules or cracks. A nail that has backed out of the roof sheathing can possibly be the source of the problem. Just be patient and thorough and you may locate your leak in this way.

A valley is the line formed when two roof planes come together or intersect. The valley system we use here in Dallas is the closed valley. Shingles overlap where the 2 slopes come together at the valley with a valley underlayment beneath for an extra layer of protection. Metal valleys are used in some places, rolled roofing is used in some areas, and the shingles are just laced together in other places. If the shingles are not properly trimmed when they are installed, valleys can eventually produce leaks. The end of a shingle trimmed for a valley has a chisel point, and if a second cut to make this point resemble an arrow point is not made, water can leak into the house by traveling along the top of the shingles. The wrapper on the shingles explains how to make the second cut properly.

When a roof stops at a horizontal wall, a metal flashing should be directing water coming down the wall away from the shingles’ ending point. The flashing could be in front of a brick wall or behind wood siding and should extend at least three inches over the shingles. Flashing should bend and extend into a mortar joint one inch when the wall is masonry or brick. If you see tar, roofing cement or caulk used with these materials, it means there has been a leak that somebody attempted to fix with them.

At the point where a roof meets a vertical wall, you will see step flashings. When each row of shingles was installed, a step flashing was put next to the wall over the shingle and then covered by the next shingle row. You should only be able to see a tiny bit of the flashings if they were installed correctly. Check these flashings for holes or rust that might indicate the source of a leak.

Chimneys are a common source of leaks because they have four different types of flashing, and if those flashings or the counterflashing into the brick mortar were not correctly installed, a leak may occur in that area. Water can run behind the flashings if it finds even a tiny crack above them. Check the flashing for soldered corners that are broken or that have holes.

Many of the newer vent flashings use a rubber seal with aluminum flashing, but the rubber may crack after 10 or 15 years. Check around plumbing pipes for cracked rubber. Flashing should go up under the shingles going up the roof from the plumbing vent, and the bottom of the flashing should cover the shingles and remain exposed.

These flashings are like the plumbing vent flashings but frequently have a metal storm collar. The storm collars should be tight around the pipe coming out of the roof, and if they are loose, they may cause leaks.

Wind can drive rain up under your roofing even when your roof is in good condition. The tarpaper can help to prevent this problem. You can hem the hidden edges of metal valleys by bending them 180 degrees to create a channel for directing the windblown rain to the bottom of the valley. You can also put roofing cement under the shingles along the roof edge on the windy side of your house. Rain driven by wind can be very powerful and cause leaks in even the best roofs.

What appears to be a roof leak can actually have another cause such as attic condensation. High humidity can be the cause of condensation and make it appear that rain is falling in your attic. It may also cause the underside of roof sheathing to seem wet. If a chimney crown acquires a crack, it may discolor the inside surface of the chimney or cause the plaster to bubble. If siding above a roof is missing, water may come in behind head flashings. These conditions may cause leaks from sources other than your roof, so you may have to do some real detective work to find the reason for your problem.

The causes of roof leaks are numerous and can occur because of the inferior installation of the roof system, items dropped on the roof causing mechanical damage, failure of roofing material, problems with the HVAC, plugged up roof drains and various other situations. Leaks are more difficult to find when the source is a few feet away from the inside area showing water damage. For instance, if water enters a hole in your asphalt shingles, it runs along with the underlayment to another hole that could be several feet away. The water then runs on the decking top to a seam or a hole in the decking. Dropping down into the attic, it runs along the ceiling top to a seam or a hole in the plaster or drywall. When you have several layers of roofing on your building or a vapor retarder at the ceiling level, the distance that the water travels before you see it inside can be even greater. Locating a leak is sometimes more difficult than you think it should be. The following guidelines can help you. When the guidelines use the words “leak area,” they are referring to an area located within 10 feet of the leak.