By: Barry Stone
Dear Barry,
Your Web site lists the 12 most common defects in homes. One of these involves firewall violations in a garage. How does a home inspector determine that the right material was used to build a firewall? -- Gary, Tennessee
Dear Gary,
In modern homes, where drywall is used for interior surfaces, a garage firewall should consist of 5/8 inch type X drywall. In older homes, a firewall will be finished in plaster. In many garages it is not possible to verify the thickness of drywall without cutting a hole in the material, and this would certainly not be permissible during a home inspection. If the firewall is physically damaged or has holes, these openings enable an evaluation of the drywall thickness. Where there are electrical outlets or switches in a firewall, the thickness of drywall can sometimes be determined by removing a cover plate.
In many instances, inspectors must assume that 5/8-inch drywall was used, trusting that the building code was properly enforced at the time of construction. If the garage attic is not separated from the house attic by an attic firewall, then the garage ceiling will be part of the firewall assembly. In that case, an inspector can verify the thickness of the drywall by reading the manufacturer's label on the attic side of the drywall.
Apart from determining that approved material was used for the firewall, a home inspector checks for unapproved type openings, such as windows, doors that are not fire-rated and self-closing, or plastic ducts that penetrate the firewall.
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