How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
How do I minimize roof penetrations?
Saturday, March 12, 2022
More roof leaks start at roof penetrations—like skylights, plumbing vents, gas appliance flues, and dryer vents—than anywhere else on a roof. Each thing that pokes through the roof surface increases the likelihood of a leak. And penetrations on the street-facing sides of the roof also detract from the home’s curb appeal. But you can reduce the number of roof penetrations when planning a new home, and then you get a second chance to eliminate some of them when reroofing. Here’s how:
•• Plumbing vents - A minimum of one plumbing vent through the roof is required by the building code, and you can reduce or eliminate the number of additional plumbing vent pipes through the roof by using air admittance valves (AAVs) and consolidating multiple vent stacks into one below the roof where possible. See What is an auto vent, air admittance valve, or check vent? and What are the code requirements for plumbing vent terminations? for more on this.
•• Bathroom and kitchen exhaust fans - can be routed to terminate through walls or soffit instead of the roof.
•• High-efficiency gas appliances - can be vented through a sidewall.
•• Dryer vents - can be terminated at exterior wall or the duct run underground to exterior. This may require locating the laundry room closer to an exterior wall. Rooftop dryer vent terminations are also problematic for another reason. They are often out of sight and difficult to reach, so roof vents don’t get cleaned regularly and become clogged with lint, which is a fire hazard.
•• Choosing electric appliances - for HVAC and water heater eliminates the flues required for natural or LP-gas units.
•• Switch to a tankless gas water heater - when it’s time to replace your old gas water heater. It can be mounted on an exterior wall or vent through an exterior wall.
•• Choose underground electrical service - when planning your home, to eliminate a rooftop service mast.
•• Install only best quality skylights - Yes, we know that a skylight is an asset that brightens the interior any home. If you choose to have one installed, make sure it has a high curb with correct flashing, and installed by a professional roofer. A cheap skylight sits almost flush to the roof and is guaranteed to leak after a few years, no matter how much caulking is slathered around it—like the one below.
While some of these penetrations can be eliminated when reroofing your home, it’s also a good idea to check in the attic for any unintentional removal of penetrations after the roof is complete. A couple of times each year we come across a dryer or water heater vent termination that was removed while installing new roofing and not replaced—with the opening shingled over—or the vent termination was replaced, but not reconnected to the flue below it in the attic. Either way, the appliance ends up venting into the attic just below the sheathing
• • • • • • • • • • • • • • • • • • • • • • • • • • • •
To learn more about roofs and attics, see these other blog posts:
of Blog Posts
Top 5 results given instantly.
Click on magnifying glass
for all search results.
Buying a home in North/Central Florida? for a team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.