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Does Your Home Have a Firewall?

November 2, 2021

A firewall isn’t really something you think about much when it comes to your home. The firewall is one of those invisible features that can save your life in case of fire. If your home was built after 1927 and has an attached garage, you most likely have a firewall.

In the most literal sense, the definition of a firewall is a fireproof barrier that stops the spread of fire from entering a space. This type of firewall would be cost-prohibitive to build, especially in residential construction, for residential purposes the firewall isn’t really fireproof, it’s fire-resistant. In other words, it holds back the fire while you get out of the house to safety. This fire-separation wall works by slowing the progress of fire into the interior walls, and other parts of the house. In many cases, these types of fire barriers can slow the progress of the fire long enough to allow the fire department to arrive and get the fire under control.

While it’s possible to have a firewall installed in any room; both the UBC or uniform building code and the International Code Council, IBC International Building Code requires the installation of a firewall between the garage and any interior living area that attaches to the garage by a common wall. The firewall requirement has been a part of the uniform building code since 1927.

Why The Garage

While most home fires start in the kitchen, the garage has the requirement for a firewall. Kitchen fires tend to be dramatic, obvious and discovered quickly. On the other hand, garage fires can start without occupants noticing, even while they are asleep.

There are many opportunities for fire problems in the garage.What is a Firewall in a House

  • Flammable items like gasoline, and paint, are usually stored in garages along with other items that create flammable vapors like; brake fluid, degreaser, motor oil, varnish, lighter fluid, and fluids containing solvents, such as paint thinner.
  • Oil and gasoline can leak from vehicles. These flammable liquids can collect unnoticed and eventually ignite.
  • Furnaces, Heaters or boilers, are often installed in garages, these units can create sparks that can ignite fumes or fluids.

With the abundance of flammable items often stored in the garage, it makes sense to require a firewall from the living areas.

How it works

Fire-resistant walls are usually made with sheetrock which doesn’t burn rapidly and slows down the rate of fire penetrating through to the dwelling areas.

A firewall is a simple structure to implement consisting of a layer of drywall. While different building code requirements allow for ½ inch drywall in the building of a firewall. The preferred standard for firewalls involves using a Type X drywall. Type X drywall is a ⅝” thick sheet of interior gypsum board that has glass fibers mixed into the gypsum in order to increase its resistance to fire.

The drywall is placed over aFirewall Drywall Exampleny of the common walls or ceiling surfaces between the garage and living areas. This includes the garage ceiling, and garage side of walls if they attach to living space. It’s important that the firewall has no gaps or voids that would allow the fire to gain access to the structure. Any drywall seams should be taped, and any air ducts passing through a firewall should consist of fire-rated materials such as sheet metal.

The garage door into the house should have a self-closing device, and be a solid wood door of no less than 1 3/8” in thickness, solid or honeycomb-core steel doors not less than 1 3/8” thick. Additionally, these doors should have a 20-minute fire rating.

Attic space and attic access are other opportunities for fire to travel into your house. It is important that any openings be sealed, including existing duct penetrations or larger openings.

Another issue related to home safety and firewalls is gas-burning appliances like a water heater located in the garage. Every area has its own rules and regulations about how gas appliances must be installed to work safely but for the most part, local building regulations will usually require that these appliances be raised at least 18” off of the floor because gasoline fumes tend to settle along the floor, raising the water heater, keeps those fumes from igniting when the appliance ignites.

How Long Do You Have?

The question of time is related to the fire-resistance rating of the materials used in the construction process. A higher fire-resistance rating, means the materials take longer to burn, while a lower fire-resistance rating simply means the materials burn faster.

Most homes have a one hour firewall. The one-hour fire rating means that an assembly or firewall consisting of various building materials can resist exposure to a standardized fire for one hour. In some commercial buildings a 2-hour area separation wall system is required. This is accomplished by using different materials which, in most cases, are too expensive for a residential project.

The firewall along with working fire alarms should allow you and your family enough time to escape in the event of a garage fire.

Firewalls in a Multi-Family Setting

There are different rules when it comes to fire safety for multi-family construction. Since these property types often have common walls, building codes generally require a minimum one-hour fire-resistance for these types of structures. This rating also applies to common ceilings and floor joists as well, for example between an upper-level condo unit and their lower neighbors.

This type of fire separation between floor levels gives residents the time they need to escape assuming the integrity of the firewall meets the prescribed fire resistance duration and was made with the approved material.

Firewalls in Older Homes

We often hear that older homes don’t require a firewall. This may or may not be true, as we have previously mentioned the garage firewall requirement became a part of the building code in 1927. So, a home built prior to 1927 would be exempt or “grandfathered” if it didn’t have a firewall between the garage and the living space.

Firewalls in older homes

Homes built prior to 1927 will most likely consist of walls made of lath and plaster. This type of wall consists of thin horizontal wood strips nailed to the vertical wall studs. The wood strips are then covered with plaster containing cement. While lath and plaster walls are not officially fire-rated, the cement used in this plaster would most likely meet modern fire rating standards.

While this doesn’t constitute a modern-day firewall it might give you more peace of mind if you own this type of home. If on the other hand, you’d like to take that extra step further you could seal any voids in the existing wall between the garage and living spaces. Of course, you could also just go ahead and install a modern firewall as well.

Home Inspection Issues around a Firewall

When buying or selling a home, you will most likely need to deal with a home inspection. Any certified home inspector will inspect an attached garage for the appropriate firewall. They will check to make sure the correct materials were used on the wall itself as well as any doors or vents that go through the wall. Additionally, they will check for any breaks in the sheetrock or voids in the wall.

If the home is an older home that does not have the appropriate firewall in place between the garage and living areas, the inspector will most likely put this on the report. The inspector is concerned with health and safety issues. The fact that the property might be grandfathered as far as building code is concerned is less important than any health and safety concerns for the inspector.

The inspector will also look at other issues not directly related to the building code but related to the occupant’s general safety.

  • It’s good to have at least one step leading up to the door from the garage. Gasoline fumes and other explosive gases are heavier than air, and they will accumulate at ground level. Their entry into the property underneath the door will be slowed by an elevation increase.
  • Any doors that provide access through the firewall should be tightly sealed in order to prevent fumes from seeping into the living areas of the house.
  • Carbon monoxide has the same approximate density as air (and often warmer than the surrounding air), and can easily rise above the base of an elevated door and leak through unsealed voids.
  • Any doors should be self-closing. Homeowners often find these doors inconvenient, but they are safer than doors that can be left ajar. While this requirement is no longer listed in the IRC, it is still a valuable recommendation.
  • If doors have windows, that glass should be fire-rated.
  • Pet doors should not be installed in fire-rated doors. This compromises the integrity of the fire barrier.

In Conclusion

A firewall is an important safety feature in any home that has an attached garage. The construction and maintenance of a firewall are really very basic but often overlooked and like most safety precautions, you don’t really appreciate it until you need it.

If you live in a home that has an attached garage, make sure your firewall is intact, this means any hole, cracks or voids should be sealed or repaired. In the event of a garage fire, your firewall just might save your life.

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