Firewall Home Inspection Concerns

The way home inspection standards address firewalls is somewhat complicated. While home inspection concerns and building code concerns regarding firewalls aren’t really contradictory, they aren’t perfectly in sync either. A firewall is an implementation designed to satisfy a double wish.

The motivation behind the Firewall Home Inspection Practice Standards is not to verify that the building code has been followed as much, but rather to determine if the dual wish is true. The first part of this desire is to prevent exhaust gases, particularly carbon monoxide, that originate in the garage from entering the living areas of a residence. The second part is based on the assumption that house fires are more likely to start in the garage; if this occurs, the desire is to isolate the fire to the garage or at least delay its spread to the house itself long enough to give its occupants, especially children, enough time to evacuate.

The abstract concept of firewall, then, is something that fulfills both parts of the protective desire. Building codes govern how the abstract idea materializes, and years of putting the codes into practice determine whether the intended goals are achieved.

Home inspection standards essentially bypass building codes and go straight to the question at hand. They stipulated that the home inspector must inspect the fire partition between the house and the (attached) garage. The accepted interpretation of “fire separation” is that a fire started in one space will spread to the other space only after a delay of at least one to two hours. Also, the time delay must be maintained for all possible paths, both directly through windows and doors and indirectly through roofs and attics.

Obviously, during the course of a home inspection it is impossible to measure fire penetration delay. Therefore, the home inspector must move a little further away from the abstract idea and use guidelines that translate the implementation of certain construction practices and materials into an expected penetration delay. What this pretty much boils down to for inspectors are concerns about the pass doors between the garage and the house and concerns about the thickness of the drywall.

Home inspectors verify that the pass door(s) have a solid core and are fire resistant. A fire-rated door usually has a label identifying it as such on the side of the door where the hinges mount. Inspection standards waive the fire rating determination requirement when the label does not exist. In any case, the solid core and fire resistance rating give a satisfactory expected penetration retardation.

It has been empirically determined that the appropriate thickness of drywall for both walls and ceilings is one-half inch. Home inspectors can’t really measure this reliably, although drywall edges are sometimes exposed in unfinished spaces and attic hatches. Here, building codes and inspection standards match, so that if a home’s construction has gone through the proper channels, the inspector can be reasonably sure that the building inspectors have checked the thickness of the drywall. .

Codes for commercial buildings and multi-family dwellings stipulate the additional requirement that the walls between units must continue through the attic to the roof. This requirement does not apply to single-family residences, even between the garage and the house. Garages typically have no attic or have an attic isolated from the attic of the house, but the author has witnessed a continuous gap over both areas.