Most Roof Leaks Happen Because of Improper Flashing

The roof flashing, which seals and protects building joints from water penetration, is more important than the roofing product you choose and it should be one of the major deciding factors when choosing a contractor. Unfortunately, flashing is virtually ignored in reroofing circles by contractors and homeowner alike.

What is Flashing?

When you think about flashing, think of braided hair—each piece contributes to the integrity of the braid. Roof flashing is often “braided” together with the shingle to provide water shedding near major roof penetrations that would otherwise leak. There are many types of roof flashing, including step flashing, wall flashing, back pan flashing, and counter flashing, just to name a few.

Why is Flashing So Important?

Wherever there is a roof penetration (hole in the roof or cut in the plywood deck) there is a high risk for a leak. How can a big chimney stick out of a roof, yet not leak? Proper flashing! How can a window/skylight be installed in a roof, yet not leak? Flashing. How can a dormer jet off of the main roof line, yet not leak? Flashing. Without excellent re-flashing practices, a roof will leak in the above scenarios.

Sadly, 99% of reroofing companies reuse the metal flashing that is already on the roof because it takes time and a lot of training to implement a proper re-flashing program. Make no mistake about it—this is not okay!

Replacing your shingles without replacing all flashing* is like fixing a leaking faucet with duct tape!

* The exceptions are wall or step flashings under the siding. Replacing these flashings can cause costly damage to the siding.

Roofs That are Not Properly Re-Flashed Leak—and This is Why:

  • There is a huge chance that the flashing was not installed correctly in the first place. Only a clean application and re-flashing can guarantee a proper installation.
  • Now that the home has been reroofed and the old shingles have been torn off, the flashing is not flat anymore. It is bent and crumpled and probably rusty.  This jeopardizes proper water shedding.
  • When the flashing was originally installed, it was nailed in. Now that the house is being reroofed, those original nail holes are still in the flashing. Unless that flashing is replaced, there will be nail holes spread around the roof penetration (chimney or skylight). This totally compromises the waterproofing at that penetration.
  • When a person buys a new roof, everything on that roof should last for the duration of the new manufacturer’s warranty. This varies based on product but it will be a minimum of 30 years. How can a rusted, crumpled, punctured, piece of roof flashing that has already been on the roof for 20 years be expected to last another 30 years? It can’t be expected to last, and it won’t last; it will cause a leak in 5 to 10 years. This is not fair to the homeowner who has paid for a roof that will last a minimum of 30 years.

How Do You Know if your Roof Flashing is Properly Installed?

Once you have made the right choice and selected a contractor that is going to re-flash all of your roof penetrations, then you need to make sure the re-flashing is done properly, which is much more difficult.  A very small percentage of roofers know how to install flashing properly, never mind homeowners having to figure it out. But here are some tips that may help an untrained eye:

  • Beware of gobs of tar. It would be really nice if your roofer used 25-year endurance, clear eavestroughing silicone on your metal flashing, because it looks better and lasts longer. But even if he doesn’t, there should not be a massacre of tar on your flashing. Water shedding is created by the shingles in combination with properly installed flashing, not by the tar.
  • Follow the 4-inch rule of thumb. Every single piece of metal on a roof should extend a minimum of 4-inches beyond the point of penetration. This is necessary to direct water away from the penetration. Many other provinces include this in the building code. The Albert Building Code is silent on this fact. As a result, most roofers don’t use this rule of thumb at all or only use 1- or 2-inch extensions. This is a major cause of flashing failing and roofs leaking. If you are not sure what this looks like, then ask your estimator to show you a sample specification of a re-flashing to clarify the matter.
  • Ensure exterior coverings are being dealt with. In order to properly re-flash a chimney, the vinyl or wood siding must be removed. If your roofer didn’t remove the exterior covering you are almost guaranteed that it’s not done right. In order to properly re-flash a skylight, the skylight must be removed. This will likely cause a little mess for you to clean up underneath the skylight inside your house. If your roofer didn’t do this, again, you are almost guaranteed that it is not done correctly.

There many other specifications for proper roof flashing. Here we have just covered a few items that may be visible to a layperson. The most important thing is that the re-flashing is redone on every reroofing job, hopefully by installers who have been trained to do it properly.