What are Roof Penetrations?

Wondering what the things on your roof are? Are you trying to figure out what your roofer is talking about when they mention penetrations?

Both questions are common in the roofing industry, and they’re both talking about the same thing. “Penetration” is a term we all know, but homeowners don’t usually hear it in the roofing context until they need a roof replacement.

So, what exactly is a roof penetration? Are there different types? 

For over 30 years, Bill Ragan Roofing has helped homeowners decipher roofer language to understand what they’re being told before investing thousands of dollars. So, let’s start with something as simple as roof penetrations. 

By the end of this article, you’ll know the answers to the following questions:

• What are roof penetrations?
• How are roof leaks prevented around penetrations?
• Do roof penetrations impact the cost of a roof replacement?

What are roof penetrations?

A roof penetration is roofing terminology for anything that comes through your roof. They are crucial for the functionality of your home’s internal systems. 

However, the types and number of penetrations on homes vary. This is simply because every penetration has a specific function that depends on the systems inside. 

Below are the most common roof penetrations and their main function. 

Vents

Vents are the most common type of penetration that every roof has in some shape or form. Every roof has plumbing vent pipes that allow gases to escape and maintain the correct pressure in your plumbing system. 

(Different pipes and vents)

There are exhaust vents for your attic’s ventilation system, which is crucial to the life of your roof and your home’s energy efficiency. Along with the attic vents, there are HVAC vent stacks that help regulate the temperature in your home. 

If you have a gas appliance, furnace, or other gas system, there will be vents to exhaust carbon monoxide and prevent it from getting into your home. 

Chimneys

Chimneys are roof penetrations that act as vents to allow smoke to escape. They are probably the most noticeable penetration due to their size and material (stone, brick, siding, etc.).

If you have a gas fireplace, there will be a vent stack for gas to escape instead of a chimney. However, it’s also common for an exhaust vent right to be behind the gas fireplace instead of through the roof. 

Skylights

Like chimneys, skylights are big roof penetrations. Skylights' main function is to let more natural light in, but certain types also provide some ventilation. 

Curb-mounted skylights have a higher profile than deck-mounted skylights, which makes them taller on your roof. So, the installation method and location determine how much they stand out. 

Satellite dishes and antennas

Satellite dishes or antennas are also considered roof penetrations. Even though the services aren’t as common, there are plenty of roofs with satellite dishes and antennas. 

To avoid potential leaks, there’s no reason to have penetrations on your roof if they’re not being used. That’s why many homeowners remove satellites and antennas during their roof replacement if they no longer get the service provided.

Solar panels

Solar panels are becoming more and more popular as roof penetrations. They’re great for generating clean energy, but installing them on the roof comes with challenges. 

A big challenge is that solar panels are usually installed by a solar company without roofing experience. So, it’s crucial to consult a roofer before drilling or installing anything through your roof. 

Another challenge is the weight of the panels. This can lead to structural damage if the roof decking is compromised before installation or if a leak rots the areas around the fasteners and mounts.

Electronic conduits

While not as common as the other, another roof penetration is electrical boxes or other conduits. Solar panels and other electrical components on your roof will have some kind of box or cable to protect the wiring that runs into your home’s interior. 

While not as noticeable or common in residential roofing, conduits are more likely to show up on commercial projects. Because of this, most residential roofers won’t touch or work around electrical components until they’re unhooked by a licensed electrician.

How are roof leaks prevented around penetrations?

While it varies, every home will have penetrations coming through the roof. Unfortunately, every penetration has leak risks if they aren’t sealed correctly. 

Every roof penetration should have ice and water shield installed around it before installing shingles for added leak protection. However, certain penetrations also need the right materials installed over or around them. 

Roof boots around pipes

For plumbing vents and other pipes, roof boots (also called pipe boots) are slid over the top and installed to the roof. This seals the pipe to prevent water from traveling down the sides into your home. 

Roof flashing

Roof flashing is installed wherever your shingles or roofing material butts against something and other leak prone areas. Skylights come with flashing kits provided by the manufacturer to install around the base. 

If done correctly, it prevents water from destroying the ceiling and drywall. Chimneys need roof flashing installed at the base, but the material determines the type. 

Brick and stone require counter flashing, while siding requires step flashing. Just know that flashing problems are a common cause of roof leaks, so it’s crucial to hire a reputable roofer to do it right. 

Roof crickets

In addition to flashing, chimneys (and other penetrations) over 30 inches wide require installing a roof cricket at the base facing the roof’s ridge. This isn’t something roofers just came up with; it’s actually a building code. 

(Cricket at the ridge side base of a chimney)

According to code R903.2.2 (Crickets and saddles) of the 2021 International Residential Code:

“A cricket or saddle shall be installed on the ridge side of any chimney or penetration more than 30 inches (762 mm) wide as measured perpendicular to the slope. Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.”

No matter what, every roof penetration must have the right material(s) to prevent water from entering a home.  

Do roof penetrations impact the cost of a roof replacement?

Roof penetrations always factor into the cost of your roof replacement. The more penetrations your roof has, the more labor and material costs increase. 

It impacts material costs due to the flashing, boots, ice and water shield, and anything else required to ensure they stay leak-free. Roof vents themselves also add to material costs and increase more if you upgrade the type. 

If you're replacing or getting new skylights completely, there will be a large added material cost. Labor costs are impacted simply because they have to be worked around, sealed properly, and (for certain ones) installed. 

No matter what, a roofer always considers the number and types of penetrations when estimating a new roof. Smaller pipes or vents won’t add that much to the cost, but bigger penetrations, such as skylights and chimneys, can add a good amount. 

What other roofing terminology do you need to know?

Now you know what roof penetrations are, the common types, how leaks are prevented around them, and how they impact the cost of a new roof. As I said, roof penetration is just general roofing terminology for anything that comes through your roof. 

However, you ended up here because you heard the term and didn’t know what it was. The roofing industry is full of terminology that homeowners have to navigate through when getting a new roof. 

Unfortunately, some roofers use this to confuse or sneak things past unsuspecting homeowners. The last thing you need is for something as simple as terminology to be the reason you get taken advantage of by a bad roofer. 

That’s why I wrote another article breaking down the terms you need to know when starting your roofing project. 

Check out Roofing Terms and Definitions: Roofing Terminology You Need to Know to understand a roofer’s language when meeting with them.