Q&A / 

Roofing – Locating a Leak

Locating a roof leak can be a really big undertaking. I have spent days trying to find leaks. On one job, it actually turned out that the roof wasn't leaking at all. The water was actually entering a massive brick chimney. It flowed down inside the chimney and eventually surfaced at some roof rafters. It then traveled along the rafters towards some skylights. Both the homeowner and I were very frustrated. Once we sealed the chimney with a high quality siloxane water repellent, the mysterious roof leak disappeared.

High School Physics

Roof coverings work in conjunction with gravity. Without the pull of gravity dragging water down the roof, most coverings would readily admit water into your house. Keeping this fact in mind will allow you to locate many roof leaks. Always look sideways, diagonally or up-roof from an inside leak location for the source of the leak.

Using a garden hose and a sprinkler will also help you. Always start from the lowest possible leak location and work upwards. NEVER point the hose up-roof! Try to simulate rain from above. Don't use an unrealistic flow of water. It may take upwards of five to 10 minutes for a leak to expose itself, so be patient.

The Most Probable Cause

Close to 90 percent of all roof leaks happen at flashings. Flashings are transitional roofing materials. They connect a roof to something that is not a roof. You will find flashings at chimneys, valleys, where a roof bumps into a wall, skylights, plumbing stacks, etc. When I am called to find a roof leak I always study the flashings before I spend any time looking in the field of shingles.

The reason flashings cause so many problems is that many roofers are like a lost ball in the high weeds when it comes to installing them. They simply do not have a clue how to do it. I have seen metal flashings installed with caulk. I have seen aluminum flashing used in masonry work. Some roofers actually use massive quantities of roofing cement smeared all over the flashings. All of these practices are wrong.

Low Slope = High Leak Potential

Many modern houses have low slope roofs - say four or five in 12 pitch. These roofs are highly susceptible to leaks from wind blown rain. If you have the opportunity to increase the pitch or slope of your roof, do so.

Repairing Roof Leaks

You would be surprised how simple it is to fix many roof leaks. Often it takes a simple piece of metal flashing. You may have to slide it over a hole and up and under the shingle above. Possibly a counterflashing has rusted. Perhaps a solder joint has cracked.

Do not even consider using roofing cement as a permanent roof patching compound. Did you know that it is not even supposed to be exposed to sunlight? Yes, UV rays break it down! Roofing cement is supposed to glue two pieces of shingle or rolled roofing together. It is not "roof icing" as I call it.

Caulk is another temporary roofing material. Don't be tempted to use this material. It works great on interior woodwork and tile, but not roofing materials. Roofs move a lot. Properly installed metal flashings account for this movement.

Look at your roof and flashing systems. Note how they resemble feathers on a bird or fish scales. The shingle above overlaps the flashing or shingle below. If you identify a leak location, form a piece of metal to cover the leak. Then slide the metal up and under the shingles above the hole. In many instances - assuming you are working with small pieces of metal - they will friction fit. There is no need for nails to hold the metal in place.

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