On a home inspection last week, I encountered an attic above the garage that was not separated in any way from the attic space above the house. Because home inspections require examination of proper fire separation between house and garage, this raised a red flag. However, this condition didn’t specifically violate anything on the standard checklist generally used by the home Inspection services.
For other home inspections, I have seen either no attic over the garage or two separate attic spaces, one over the house and the other over the garage, with separate access hatches. But just because a practice differs from what occurs in a typical home inspection does not necessarily imply it is wrong. After all, this was a newly built home and presumably passed county building inspections, so further investigation was warranted.
Home Inspection Requirements
Home inspection standards in Austin, TX mandate that the home inspector should inspect fire separation between the house and garage when applicable. The ‘when applicable’ part means attached garages only. The ‘fire separation’ part of the home inspection standard means that a fire started in one space will not spread into the other space for at least a certain duration, typically one or two hours.
Because the potential for flammable vapors to ignite is higher in the garage than in the house, fire separation is a safety precaution primarily intended to keep the garage fires from spreading quickly into the house, thereby, allowing the occupants sufficient time to vacate the house. This time delay must be achieved through all possible paths, both direct, walls and doors, and indirect, ceilings and attics.
Implications for the Home Inspection
Unfortunately, one can’t measure delay of fire penetration during a home inspection. But guidelines translate the delay requirement into measurable construction practices.
The most straightforward practice to check is for a solid-core, fire-rated pedestrian door between garage and dwelling. Such doors usually display a fire-rated label on the edge where the hinges mount. Home inspection standards do not require the home inspector to determine if unlabeled solid-core doors are fire-rated.
Practice for walls and ceilings is for at least 1/2″-thick drywall. This is more difficult to verify on a home inspection, although attic hatches often provide a way to check drywall thickness, at least for the ceiling.
In case of the open attic space between house and garage, it turns out that, although building codes require walls to continue through attics to the roof in commercial and multifamily dwellings, such separation in residences is not necessary so long as the ceiling drywall thickness condition is met.