Planning to drywall my garage wasn’t as simple as throwing some drywall panels on my wall and calling it a day. Even determining what drywall thickness to use meant that I had to navigate several building codes to find the answer.
Fortunately, if you understand these codes, it makes picking the correct type of wall really easy.
Garage walls that connect to your home are required to have a fire separation wall, typically a ½-inch gypsum board. Living areas above the garage will need 5/8-inch Type X boards on the garage ceiling. Additionally, moisture-resistant drywall may be required if you live in a flood-prone or damp area.
Although garage drywalls are governed by Section 302.5 of the International Residential Code, choosing the right drywall is more than just a bureaucratic tick-box process.
There are genuine and practical benefits that come with following the codes that may save your house from burning down in the event of a fire.
Choosing The Right Drywall For Your Garage
Fortunately, there aren’t endless drywall options for a garage, so you can quickly figure out what type you need by considering your garage layout.
Start by answering these questions:
Do you have an attached or built-in garage? If so, is your garage attached to your house next to or at the bottom of the house?
Attached and built-in garages require a fire separation wall to help isolate the garage from the rest of the house.
What Is A Fire Separation Wall?
The typical home garage is a collection of fire hazards, which get worse depending on what you use your garage for. So the intent behind a fire separation wall is to help contain the fire in the garage.
Don’t confuse a fire separation wall with a complete firewall.
A firewall blocks off a fire entirely, while a fire separation wall slows down the fire’s spread, buying time for the fire department to get on the scene.
Typically, a fire separation wall should contain or retard a fire inside that room for an extra 30 to 60 minutes before failing and allowing the fire to burn through.
Fortunately, gypsum drywall boards have a built-in fire resistance level, which means they burn less quickly than you think. This is because there isn’t a lot of flammable material inside them apart from the paper on the surface.
What If Your Garage Is Next To a Living Area?
If your garage is attached to the rest of your house, you must use gypsum boards to create a fire separation wall.
The drywall panels have to be at least ½-inch thick. Otherwise, they won’t withstand the heat from a fire long enough to meet the 20-minute requirement.
The same applies to separating your garage and the attic above it. Ideally, you want to keep a fire from getting into the rafters of your roof. Once the rafters start to burn, the fire can spread between rooms above the walls.
For this reason, it is also a requirement that when you build a fire separation wall, you extend the boards all up to the roof sheathing to slow a fire in the rafters.
What If Your Garage Is Underneath a Living Area?
Remember your childhood science classes when your teacher explained that hot air rises?
Fire acts the same way, burning upward.
If there is a fire in your garage, the ceiling must handle considerably more heat than the walls. If an attic is above the garage, this isn’t necessarily a life-or-death problem.
However, if your house is like mine, the main bedroom is directly above the garage. That becomes a big issue if a fire breaks out in the middle of the night.
That’s why the thickness requirement increases from ½-inch gypsum board to 5/8-inch Type X boards.
Type X drywall was explicitly designed to be even more fire-resistant than the typical gypsum boards by adding a fiberglass core to the board to add resistance.
While they will not completely prevent a fire from burning through them, they offer more time for you to react.
What If You Have a Detached Garage?
If your garage is more than three feet away from your house, you technically no longer need a fire separation wall.
However, since the separate garage has its own supporting walls, the rule for supporting walls is the same as the requirement for fire separation walls.
In other words, you will still need to use a gypsum board at least ½-inch thick.
Consider Adding A Sound Proof Layer To Your Drywall
A final tip for choosing drywall is to consider adding a soundproof layer to your fire separation walls.
This is an excellent idea if your garage doubles as a workshop to help keep at least some of the noise inside the garage and less distracting to the rest of your family.
This is also good if your garage doubles as your getaway family cave. In this case, you can keep the noise of the busy house out of your garage and away from your precious movie or reading time.
There are various options for soundproofing that include different types of drywall boards.
Just ensure that the boards you choose do not interfere with the fire separation boards. In other words, there’s no point in having a fire separation wall if you stick super high fire risk boards on top of it.
Wrapping It Up
According to section 302.5 of the IRC, a garage attached to your house needs a fire separation wall made from gypsum board that is at least ½-inch thick.
However, if the garage is underneath your home, you must use 5/8-inch Type X fire-resistant boards to help prevent a fire from spreading into your house.
