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Matthew Steger WIN Elizabethtown

Garage Fire Separation (Firewalls)

Garage Fire Separation - The Hidden Hazards

Modern construction standards require “fire separation" (sometimes called a “firewall”) in an attached garage to separate the garage from living space and/or an attic. Its function is not to stop a fire, however it is designed to help slow a garage fire’s spread into the home (either directly into the living space or through an attic, crawl space, etc. located near the garage) in order to give occupants sufficient time to evacuate. In most cases, proper fire separation would consist of 1/2” or thicker drywall mudded and taped as well as the mandoor from the garage into the home being fire-rated. If living space exists above the garage, the fire separation should be at least 5/8” thick Type –X drywall which has a longer (60 minute) burn time. A concrete block wall between the home and garage will also help slow down a fire’s spread to the home assuming the block wall extends fully to the roof and is fully intact (has no openings).

Fire separation walls/ceilings also are designed to help prevent dangerous exhaust fumes, such as carbon monoxide, from entering living space. That is why any openings in the garage walls or ceilings common with living space or an attic where wiring, plumbing, or ductwork penetrates or any other holes should be properly sealed, such as with fire-caulking (a high temperature-rated sealant). The drywall doesn’t need to be painted, but at least properly mudded and taped.

A common defect I that run across, sometimes even in newer homes, is when there is attic space above the garage and the access cover from the garage consists only of a piece of particle board, OSB, or plywood. Each of these materials is combustible, so having a wooden access cover separating an attic and garage compromises the fire separation. Even if the rest of the garage ceiling or walls are drywalled, any unsealed opening or combustible material can compromise the fire separation. Replacing a wooden access panel (also known as a scuttle) cover with an appropriately-sized piece of drywall is a proper repair, however, and a recommendation that I regularly make during home inspections when I find wooden access covers in garages.

Another common defect pertains to pulldown ladders installed in garage ceilings. These covers are almost always wooden (and therefore combustible) which will compromise the garage fire separation since, again, the pulldown ladder's wooden cover will likely quickly burn and allow a fire to quickly spread. Pulldown ladders with steel covers do exist and should help provide better fire separation, however I have only seen a 1 or 2 of these steel ladders in many years inspecting homes. Simply installing a piece of drywall or steel over the pulldown ladder’s wooden cover doesn’t provide the needed protection barrier since there will still be unsealed seams along the edges for fire or carbon monoxide to penetrate through. Also, the added weight of a piece of steel or drywall will likely cause the ladder assembly to hang down slightly preventing a tight seal.

The above photo shows an installed pulldown ladder; the wooden cover is combustible and will allow a garage fire to quickly burn through this wooden cover and enter an attic or nearby living space. The amount of time that properly fire separation garage ceiling may provide for emergency egress versus one that is compromised by a pulldown ladder with a wooden cover may mean the difference between getting out safely and being a casualty.


The wall common in the above photo between an attached garage and the home has several issues: (1.) plywood separates the garage and the kitchen (plywood is combustible), (2.) white ventilation grate at the the bottom of the plywood (installed to allow the refrigerator to vent to the garage), and (3.) the window between the garage and the home could shatter into the home due to a garage fire. Carbon monoxide from the garage could also readily enter the home at these areas as well.

Of course, a home inspection is not a code compliance inspection, however I have inspected several new or recently-built homes that have passed the township or borough code inspection only to find an improper garage attic access cover (such as plywood, OSB, or particle board) installed. A few times, I was able to find who performed the code compliance inspection of the property and inquire as to why the void in the fire separation wall or ceiling passed their inspection. Each time, I was able to determine that the issue was something overlooked (aka "missed") by the code official that should have been caught and repaired prior to occupancy. This is a good example of why even brand new homes should have a professional home inspection performed.

The mandoor from the garage into the home should also provide proper be fire separation. This should be a solid core wooden door (1 3/8" minimum thickness) or a steel fire-rated door, unlike the thin hollow wooden door in the photo below. A metal fire-rated door often will have a sticker on it indicating that it meets a specific fire code; sometimes the sticker has been removed or painted over. This garage mandoor should not have a window (unless the window glass is explicitly labeled as being fire-rated) nor should it have any other openings, such as a pet door. Standard glass will not withstand a fire and may shatter into the home, although there are some mandoors available that have fire-resistant tempered glass in them, although these seem to be very rare. Pet doors present issues similar because they are not air tight plus these doors are often a combustible material (such as plastic). Again, carbon monoxide and/or fire can easily spread into the home at these pet doors. Some homes also have firewood pass-through doors which allow firewood to be brought into the home directly from the garage; all of these that I have run across have wooden covers which are combustible and will void the garage fire separation requirement.

This garage mandoor (above) into the home is a thin wooden door, like you'd see installed into a bedroom. The door would likely burn in a matter of minutes and provides no protection to help slow down a garage fire from spreading into living space. Also, the gap under door will not stop possible carbon monoxide entry into the home. For a door to achieve a 20-minute fire-rating it has to go through testing procedures by Underwriters Laboratories and then it receives its “UL listing” as a fire-rated assembly. All 4 sides of garage mandoors should be properly weather-stripped to prevent air from the garage (possibly containing carbon monoxide) from entering living space. Also, garage mandoors may never connect directly to a bedroom. Some areas require garage mandoors to be self-closing, but I am not aware of any city or township in PA that requires this feature.

This mandoor between an attached garage and living space may provide fire separation if not for the non-fired rated glass. The glass would likely shatter into the home in the event of a garage fire thus allowing fire and/or carbon monoxide to then enter the home.

Since PA didn’t have a uniform construction code until 2004, most homes in the Commonwealth didn’t have to meet any code when they were built. The lack of proper fire separation is not uncommon in homes built prior to 2000. Although homes built prior to a building code would be most likely be grandfathered, I still bring up the issues with my clients to inform them of these potential safety issues that they should be aware of.

In many bi-levels built in the 1990s and before, for example, I often only find exposed insulation and the main level’s floor joists separating the garage from the living space above. In other words, these types of homes often have no fire-separation installed at all. A garage fire could reach the adjacent living space in less than a minute. Unsealed openings, or no fire separation at all, can lead to carbon monoxide infiltrating the home as well.

Openings where ductwork, plumbing, wiring, etc. pass through garage ceilings and common walls should be properly sealed, such as with a fire-caulking. Ductwork in garages that penetrate common walls or ceilings should be a minimum of 26-gage steel. There should be no openings in this ductwork since fire or carbon monoxide can enter. In a few homes I’ve inspected, I’ve seen heating/cooling systems installed in garages that have unsealed openings for an air filter within the garage. Again, a potential location for fire or carbon monoxide entry into the living space.

This is an unsealed opening in a garage ceiling where wiring from a garage door opener passes through. The hole is large enough for carbon monoxide or fire to possibly enter the garage attic and then infiltrate the adjacent living space. A proper fire-caulking can be easily applied at this location to seal off the opening.

Many townhome communities are set up with multiple attached adjacent garages. In this situation, fire separation should be installed on the common walls and ceilings of the home that the garage serves as well as at the wall separating the two garages (including the separation walls in the garage attic). Fire separation may also be required in detached garages if the detached garage building is less than 3’ from the home. In that case, fire separation would most likely be required at the detached garage‘s interior side wall (and possibly the ceiling) on the side towards the home. If the detached garage is not fully detached, for example, it has a breezeway roof attaching it to the home, the fire separation may also be required at the common wall.

In buildings with multiple units (such as duplexes, condos, townhouses, and rowhomes) proper fire-rated assemblies (firewalls) should exist to separate each home from the adjacent home(s) and should run from the basement floor all the way to the roof. These common walls help slow a fire's spread from one unit to the adjacent units. These walls often consist of either concrete block or doubled drywall on both sides of the common wall.

As part of a home inspection, the home inspector should evaluate the installed walls and ceiling of the attached garage. Proper fire-separation should exist, such as confirming continuous mudded and taped drywall is installed at the common wall(s) and ceiling. Any unsealed openings, duct registers, improper attic access panels or covers, etc. should be reported as these can compromise the fire-separation. In a garage that is not vacant, shelving or stored items, appliances, etc. may block the inspector's access to some of the walls.

When I discuss the importance of garage fire separation during my inspections, I add that ‘a fire doesn’t care when a home was built or what code was in force on that day’. In most cases, even if the home predates fire or building codes, proper fire separation can be installed or an access panel or garage mandoor can be replaced with proper fire-rated materials to give you or your family a better chance of surviving a fire. Neither of these tasks will break the bank and the extra minutes of fire separation that a firewall can provide may be just what’s needed to escape should a garage fire occur. Minutes can mean lives.

Short video about garage fire separation (firewalls):

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© 2014 Matthew Steger


Matthew Steger, owner/inspector of WIN Home Inspection, is a Certified Level 1 Infrared Thermographer, an ASHI Certified Inspector (ACI), an electrical engineer, and a US Dept. of Energy Home Energy Score Assessor. He can be reached at: 717-361-9467 or msteger@wini.com.

WIN Home Inspection has provided a wide array of home inspection services in the Lancaster, PA area since 2002. This article was authored by Matthew Steger, ACI - owner of WIN Home Inspection in Lancaster, PA. No article, or portion thereof, may be reproduced or copied without prior written consent of Matthew Steger.