Giovanni Valle is a licensed architect and LEED-accredited professional and is certified by the National Council of Architectural Registration Boards (NCARB). He is the author and managing editor of various digital publications, including BuilderSpace, Your Own Architect, and Interiors Place.
A roof drip edge is one of those small details that many people overlook. But minor as it may seem, the drip edge is an important part of keeping a building in good shape – and avoiding costly repairs in the future.
Drip edges have been required by the International Residential Code since the 2012 revision. Most states in the U.S. have adopted the IRC, which means that drip edges are required for most buildings in those states.
Because of how important it is, a drip edge is something that any building owner should consider. But legally speaking, there are some situations in which a building doesn’t need to adhere to this aspect of the IRC. A lot of it depends on the age of your building, its status, and what you plan to do with it.
What is a Drip Edge?
If you’re a contractor, home inspector, or just a knowledgeable homeowner, you probably don’t need to ask this question. But if you feel green when it comes to construction topics and you’re concerned about your home or one you want to buy, learning what drip edge is might help you figure out if it’s required for your building.
Drip edge is a strip of sturdy, rust-proof material that’s installed along the edge of a roof. It’s usually made of metal, but plastic, vinyl, and fiberglass can also work. The main function of a drip edge is to keep water from getting under the shingles as it drips down the roof. It also offers protection during heavier storms, when rain is being driven by the wind.
Until the IRC included requirements in its 2012 revision, the choice to install drip edge or leave it out was entirely up to the installer. Shingles and eaves were often the main concern, while the drip edge was simply an afterthought. But over time, roofers have realized just how important this component can be. This is probably the main reason it became a legal requirement.
Where is a Drip Edge Required?
According to the International Code Council, 49 states in the U.S. have adopted the IRC, along with Puerto Rico, Guam, the U.S. Virgin Islands, and the District of Columbia. Wisconsin is the only state that hasn’t followed suit.
Wisconsin has its own building code, but it doesn’t specifically mention drip edge. In Section SPS 321.28, which details the requirements for roof weather protection, it simply mentions that “flashing shall be installed at the junction of chimneys and roofs, in all valleys, and around all roof openings.” It then goes on to explain the requirements for each of these situations.
Because drip edge is a type of flashing, this is an ambiguous situation. If you live in Wisconsin and you’re wondering if your building should have drip edge, you should consider getting advice from an expert—or just playing it safe and getting it installed anyway.
Why is a Drip Edge Required?
As mentioned above, drip edge has a number of important functions, and having it in place helps make a roof and the building overall more resistant to weather.
It Helps Direct Running Water
Try filling a glass with water. Then tip it slowly until the water just barely begins to trickle into the sink. Notice how the water doesn’t fall straight down out of the glass? It runs down the edge of the glass first, almost as if it’s sticking to it.
The same thing can happen with water running down shingles when it’s raining. If no drip edge is installed, the water trickles to the edge of the roof, then clings to the shingles slightly as it runs off. It ends up underneath the shingles, often working its way to the fascia, where it can cause wood rot and, eventually, leaks in the building.
It Keeps the Wind at Bay
Wind is a powerful force, especially at high speeds. When it drives rain at an angle, your roof has more to deal with than just runoff. It also has to keep away water that’s trying to force its way sideways under your shingles. Drip edge acts as a shield against this sideways rain.
High winds can also tug at your shingles, lifting them and eventually pulling them off. A properly nailed drip edge goes a long way in securing your shingles in storms like these.
It Keeps Pests Out
When colder weather arrives, many animals seek out warm places to spend the winter. You don’t want one of those places to be your attic! Unfortunately, this has happened to many people without a drip edge on their roof.
In the absence of drip edge, there’s bound to be a few small gaps between the roof sheathing and the fascia. Animals sense the heat leaking out of these gaps and decide there must be a warm place to stay inside. They will then chew through whatever they have to in order to get inside. Of course, with a barrier like a drip edge in place, the gaps will be covered, and animals will have no way in.
A roof without drip edge has much less protection from these elements. This poses a risk to the integrity of the building and, in the end, the safety and health of its occupants. These concerns are probably the main reason why drip edge is a code requirement in so many places.
When a Drip Edge Isn’t Required
Other than Wisconsin residents, there are plenty of other people who might not be required by law to have drip edge installed.
For example, Article 1 of the U.S. Constitution prohibits ex post facto laws. This means that people can’t be punished for something they did in the past, as long as that thing was legal at the time. This restriction applies to all laws, including building codes.
If you’re living in an old house and wondering if you’ll get in trouble for not having drip edge, this should put your mind at ease. Since it wasn’t required when the house was built, it isn’t required now.
Building codes are also frequently relaxed in the case of historic buildings. If installing drip edge would damage or detract from the historic value of such a building, there’s a good chance it won’t be required.
None of this is to say that you should overlook drip edge just because you aren’t forced to install it. It’s still an excellent way to prolong the life of almost any building. You should consider all the benefits you’ll be leaving behind before deciding against it.
Check with an Expert
The law is an incredibly complicated thing, and building codes are no exception to this. Unless you happen to be extremely familiar with the code in your area, you should ask for advice from someone who is. City hall might be a good place to start, as they can inform you about the general requirements of the building code.
But nothing beats personalized help. If possible, you should also talk to a real estate agent or home inspector. They’ll be able to assess your unique situation and make a more informed decision about whether you need drip edge installed.
And if you’re still not sure, why not install some anyway? It’s not very expensive, and it’ll probably save you the cost of repairs later on. Besides, when it comes to the law, it’s better to be safe than sorry.
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