Where Is My Leak Coming From?

Answering: How do I find the Leak in my Roof?

The short answer to a long-asked question is you really must have a professional roofer inspect the roof to properly locate the leak. However, through the explanation of an old concept, this article will help you better understand where to look to find the leak in your roof.

Signs of Water Damage

The first step is to identify water damage in your building. So, you look around your building and notice dark, dirty circles that aren’t exactly forming a designer-made pattern (at least you don’t think they are) in random locations on the ceiling. Then you look closely at the wall. You see an area of paint that looks like it has separated from the drywall and has formed a bubble behind the layer of paint, falling slowly from the ceiling (literally water moving down between the paint and drywall). Maybe you decided to do some renovating and start tearing down a wall because why not?! You own the building. You can do whatever you want. But once you start the exciting beginning of a dreamed expansion, you find rotted wood. It tears when you put a screw in it or squishes when you poke it. Then you look down where you’re standing and see that the floor is soft too. And you follow it up and see that even the attic insulation stinks from mold. This is going to be expensive.

Suspected water damage from a leak in the roof often looks like:

  • Dark circles on the ceiling
  • Running, washed out, or bubbled paint on the wall
  • Flooring damage that matches dark circles on the ceiling
    • Damaged flooring: wood floors turn dark, vinyl floors may start to peel up and carpet will likely contain mold if it was left wet. Cement floors may show signs of collected dirt where water once stood.
  • Musty/moldy attic smell: a sign of water in the insulation
  • Rotted/spongy wood in the walls or ceiling


Yeah, you’ve got some signs. But hey, you didn’t get to where you are by being complacent. So, you find your way onto the roof to look for an obvious leak so you can (hopefully) slap some tar on and move on. You walk to the corner of the building where the leak is and see… nothing. So where is the water coming from?


Water Path

Water is a living breathing molecule whose life is guided by gravity. But we knew that: water goes down. That’s the long known, concept of gravity. So why isn’t there standing water near your leak in the corner of the office? Or some clear hole in the roof where a stick fell and pierced the roofing material. Let’s rewire your thinking of the movement of water and find out what happened.


Capillary Action and Your Roof

Why does capillary action affect your roof leak? Capillary Action is defined by usgs.gov as “the movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension.” Think of cohesion as the force that makes water molecules stick together and adhesion as the force that makes water molecules stick to other things. So capillary action happens when the adhesive force is stronger than the cohesive force. It draws that water up, up and away! from the path the water may normally take (from gravity). Did you step in a rain puddle before you climbed on your roof to look for the leak? Did your pants soak up water past the height of your shoes? That’s capillary action.

Capillary Action VS. Gravity

Gravity causes things to fall, or in other words: gravity finds the shortest and quickest path toward the center of the earth. Water is going to do just that using cohesion between water molecules until a stronger adhesion force acts upon it. Now picture your roof. All roofs have a slope of some kind whether it’s a steep slope or a gentle, low slope. Water hits the roof and begins to follow the slope towards a drain or gutter (cohesion). It does this, that is, unless it finds a shorter, quicker route to the center of the earth, such as a pinhole in that outer layer of the roof. Once it travels into that gap in material is contacts more roofing material, which, if its porous will break the surface tension and draw the water in (adhesion). The water travels based on whichever force (gravity, adhesion, cohesion, surface tension) is strongest and boom, the process continues until eventually that water makes its way to the ceiling of the corner of your office. This is why leaks aren’t always right above the sign of the leak inside the building.

Common Area for Roof Leaks

Another area of your roof that water commonly causes damage to your building is the eve edge. For example, when water reaches the edge of your roof, it likely doesn’t drip straight to the ground (using cohesion and gravity). Here, water will follow the eve edge (using adhesion) even when it is sloped down. If there is an absorbent material like wood, for the water to absorb into, then it will do just that and wind up heading right back towards your building with the potential to cause damage (insert: water damage in your office). So, you see, the water path isn’t always as simple as we wish it was, which can make finding a leak more difficult.

Where is Water Getting In?

With this understanding of water movement, we can’t make any assumptions of where the leak is coming from based on the visual signs of the water damage you see inside the building.


The industry truth is that leaks can be very challenging to find. Sometimes we can make repairs and they work on the first try, and other times we must try a repair and then wait until it rains to see if it holds up. This is why roof repairs aren’t usually held under warranty. A new roof system on the entire roof is the only way to fully ensure that all the leaks are taken care of. But a new roof isn’t always in the budget, so you have to settle for repairs, a little patience and some trial and error. As a building owner, you likely don’t have time to waste on your own system of trial and error. Climbing onto the roof regularly with every rainstorm can be time consuming and aggravating. When you’re ready to outsource this frustration to the guys who get it, give us a call.

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