Flashing Under Shingles or Improperly installed roof flashings.

What does this mean?

Flashing under shingles are the galvanized flashings that waterproof holes on the roof where vents, pipes, and other objects pass through. Although the flashings can also be made of rubberized materials or other non corrosive materials, the most widely used flashings are made of galvanized metal.

These flashings have a very specific way of being installed so that they prevent moisture into the attics or framing and allow water to drain off down the slope of the roof.

Proper and Improper Flashing Installation.

Inspectors will call an improperly installed flashing as “not serviceable”, “improperly installed”, and/or other more descriptive terms like “The flashings at the roof vents were installed completely under the shingles,” etc.

As shown in the first picture, the lower waste and exhaust vents passing through the roof (red arrows) have the shingles installed completely around over the flashings, while the vents for the attic ventilation near the ridge at the top (green arrows), show the lower edge of the flashing correctly installed over the shingles and the sides and top edges of the flashing are under the shingles.

The installation of the flashing as pointed by the green arrows will allow water to drain down over each layer of shingles, while the flashings installed as shown by the red arrows, rely solely on the longevity and proper application of the sealant applied around the flashing and the vents.

What about having another layer of shingles below the exposed layer?

On the pictures shown here as an example, the roof did have another roof layer installed beneath. However, assuming that the lower layer will prevent leaking if water passes through the vents is not sound. The reason the visible layer was installed on the first place was because the first layer was old and/or allowed leaking in the past.

But the roof was installed “professionally,” I have a permit!

Improperly Installed Flashing and vent

A large number of homeowners that have this issue on their home will typically be surprised and angry at an inspector when he/she calls this issue as a problem. Especially the home owners that hired a “licensed roofer.” I personally have been told that I was a “bad” inspector and that I did not know what I was doing because the roofer said it was done right.

Fortunately, there are accepted standards and installation instructions provided by manufacturers that detail the installation process of a roof.

Well the roofer said the installation was to code!

The bad thing about a statement like this is that the Uniform Building code and the International Residential code have nothing that details or encourages this type of installation of the flashings.

The Uniform Building Code says the following in regards to flashing: UBC1997.1509 – Other Flashing. At the juncture of the roof and vertical surfaces, flashing and counter-flashing shall be provided per the roofing manufacturer’s instructions and. When of metal, shall not be less than 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal.  

The International Residential Code says it in slightly different way: IRC2003.R903.1 General. “Roof assemblies shall be designed and installed in accordance with this code and the approved manufacturer’s installation instructions such that the roof assembly will serve to protect the building or structure.” R903.2 Flashing. “Flashings shall be installed in such a manner so as to prevent moisture from entering the wall and roof through joints in copings, through moisture permeable materials, and at intersections with parapet walls and other penetrations through the roof plane.

Both codes (one of the two should have been in effect for any construction built since 1990 in any jurisdiction), specifically defer most of the installation requirements to the instructions of the manufacturer of a roof. The code itself does not give specific instructions on how the flashings around roof penetrations need to be installed. However, roof manufacturer’s instructions do.

So for “Code” compliance, one has to look at what the installation instructions from the manufacturer specify. Companies like Certainteed and Owen’s Corning provide detailed instructions on their website and their product packages for their products installation.

Proper Installation of Flashing around Vents.

Certainteed for instance, describes in detail the sequence for the installation of the flashing around vents and Jack Stacks in their installation document. (click the downloadable link below).

Since there is no manufacturer that will specify the flashings to be installed as shown on the sample photo with the red arrows, that type of installation would not and does not meet any code requirements.

OK, so it is wrong. How can it be fixed?

Attic Vent Flashing. Properly Installed

The correction of this issue for roofs with asphalt shingles can be done fairly easily actually. One of the ways is to cut the shingles covering the lower edge of the flashings and sliding another section of shingles under the flashing edge. Adding adhesive to the edges of the shingles and flashing and under the lower edge will insure that it stays in place. Another possible way is to buy a new flashing for the waste vent stacks and sliding it around the vents, cutting the shingles around the old flashing and properly inserting the new flashing in place.

Who can do this?

Since we are talking about a roof, climbing on a ladder is going to be needed. Any time there is a risk of injury involved like falling off of a roof, the best thing is to hire a licensed “qualified” roofing contractor. Preferably someone that does not try to convince you that the roof flashings are installed correctly.

My roof is not asphalt, this does not help me or does not apply to my roof.

All roof manufacturers and accepted standards like the ones published by RS Means (Residential & Light Commercial Standards, 2^nd Edition), and the NRCA (National Roofing Contractors Association) have detailed information as to the proper method and accepted quality of   construction and materials for most applications. Metal roofs, tile roofs, wood roofs all have specific flashing installation instructions but neither of them accepts the flashings to be installed as demonstrated in the sample photo in this article with the red arrows.

What about sealing the gaps to prevent leaking?

This is a “band-aid” correction and would have to be done annually to insure there is no leak through a failed seal. Not practical!

Below is a link to the instructions provided as PDFs as published by Certainteed’s website. All instructions are the ownership of the manufacturer as mentioned within the instructions. AskHomepedia.com does not claim any copyright to these documents and are only provided through this site to allow access to the readers as it is made publicly through their website.