Leaks Around Dormers Is a Very Common Service Call

improper dormer flashingDormers can be found on most homes in the DC Metro Area. Though they are commonly found on shingle vs cedar shake roof installations. Dormers are actually in fact a roof penetration. The same as vents, skylights, or a chimney, they all have to be flashed.

As you read this article, you will understand that a dormer must include properly installed flashing along in areas where water is more vulnerable to leak. Which is everywhere. Below we dive further into this issue so you can have a better visual of why dormers will leak and become such a problem.

What Are Common Mistakes Made When Flashing Around a Dormer?

strip flashing around dormerThe strategy for installing a roof around a dormer is the same whether the roof material is:

  1. Asphalt Shingle Installation
  2. Cedar Shake Custom Roofing
  3. Slate Roofing


Roofs leak in many different places are common. It is common for stormwater to leak alongside dormers on homes in the Washington DC and Maryland area. The leak is usually caused by flashing around the dormer area being improperly installed or nonexistent. The best way to repair a roof leak around a dormer is to use step flashing. What is Step flashing? Step flashing is a structural metallic barrier between the walls of the dormer and the roof. In the picture to the right, you can see where the roofer installed straight flashing. Which ended up costing the homeowner to pay for a premature roof replacement due to the age and extensive damage.

General Contractor vs Roofing Specialist

The first mistake anyone can make is hiring an inexperienced roofer or general contractor to work on your roof. They are notorious among professionals for cutting cost and not fully completing the job. Installing roof flashing is critical in keeping a house dry. An experienced roof contractor will flash all vulnerable areas around your dormer. Majority of roof leaks around dormers are caused by improper or nonexistent flashing. A commonly made mistake is installing straight flashing. This technique is easy to install and allows general contractors to cut cost and corners. Leaving the final product looking good to a homeowner who isn’t familiar with the installation. After a couple years though, they are guaranteed to have problems.

What Constitutes Correct Flashing Around a Dormer?

step flashingA complex flashing technique called “Step Flashing” is primarily used for waterproofing chimneys. But this style of flashing should also be applied to dormers. Step flashing will redirect the water back onto the shingle to drain into you custom gutter and downspout system. If one piece of flashing happens to fail, the flashing and shingle woven in under that will just take over. This is why step flashing is so efficient. Even if one piece fails you don’t have to worry about leaks in your home. But if you have straight flashing installed, you’re going to have issues sooner than later.

Repair vs Replacement

If your roof was not flashed properly, it will be necessary to remove shingles from around the dormer during the repair. Once the shingles are removed, flashing can be placed and the shingles can be re-installed. The average life expectancy of a shingle roof in the dc metro area is 15-25 years depending. And what is the average cost to replace a roof in the DMV? If your roof is near 15 years old or older it may be better to put your money into a new roof.