How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

What are the code requirements for fire separation between an attached garage and the house?

Tuesday, December 4, 2018

There are requirements for the walls and ceiling, door to the house, HVAC ducts, and any other garage/house penetrations. Let’s take them one at a time:

WALLS AND CEILING - The wall between an attached garage and the house living area is required to be minimum 1/2” drywall. Most garages have a ceiling secured to the bottom chord of the roof trusses or rafters, and that has to be 1/2” drywall also. If there is no ceiling and the roof structure is exposed in the garage, then the wall separating the garage from the dwelling must extend up to the underside of the roof sheathing. There is a high incidence of fires started in garages due to the gasoline and other flammable materials often stored there and, either way, the intent is create a 1/2” drywall barrier between the garage and house for fire protection.

    Only common walls between garage and house (not perpendicular walls) must meet this requirement. If a garage is detached, but within 3-feet of the residence, any walls within 3-feet must have 1/2” drywall. When there is a living area (habitable space) above the garage, the ceiling requirement ramps up to 5/8” Type X fire-rated drywall.

      While all of this is intended to create a fire barrier between garage and house, it is not specified as “one-hour rating” or “fire wall” by the Residential Editon of the Florida Building Code (FBC) or the International Residential Code (IRC). It is called a “separation."

    Here’s Table 302.6 from the Residential Edition of the Florida Building Code that spells out these requirements. The International Residential Code table is similar.

DOOR TO HOUSE - This is the only place where any fire rating is specified. If the door is not solid wood or steel/honeycomb and at least 1-3/8” thick, then it must have a 20-minute fire rating. By the way, cutting a hole in the door to install a pet-door flap voids the 20-minute rating. Installing a steel door with a glass panel in it also voids the rating unless the glass is fire-rated too, which is obtainable but very expensive. See our blog post What are the building code requirements for a door from the garage to the house? for more on this.

HVAC DUCTS - Any heating/air conditioning ducts that serve the residence cannot also have registers (vents) in garage. Any register would provide a direct route for a fire to move from the garage to house. A separate HVAC system that serves only the garage is acceptable.   

    Furnaces and air handlers are often installed in the garage, and the code requires the ducts to be either minimum no. 26 gauge sheet steel, or rigid nonmetallic Class 0 or Class 1 board, or other material approved by the AHJ (building department).

     "Class 0" is defined as air ducts and connectors having burning characteristics of zero.  "Class 1" means air ducts and connectors having a flame-spread index of not over 25 without evidence of continued progressive combustion and a smoke-developed index of not over 50. The duct boards are marked with their class rating as an imprint or sticker on the board.

     Any type of register or grille in the ceiling of the garage that opens directly into the attic over the home is not allowed. We occasionally see vents retrofitted to provide ventilation to cool a hot garage in the summer, or to provide combustion air for a gas furnace or water heater in the garage. Shown below is an example of what not to do (a grille cut into pull-down attic ladder), and an example of the right way to add a vent a register in the ceiling of garage that connects directly to a roof vent via a metal duct, viewed from the attic.

    Combustion air (also called “make-up air”) can also  be provided by a vent through the wall. The two photos below show an outside and inside view of an example of this.
OTHER PENETRATIONS - Required by 3.2.11, Item 4, of FBC that any openings around vents, pipes, ducts, cables, and wires at ceiling and floor be sealed with an approved material (approved by AHJ) to resist the free passage of flames and products of combustion. The material filling the annular (ring-shaped) space around the penetration does not have to meet the ASTM E136 standards.

    Also, see our blog post Does an attached garage that is only used for storage or as a workshop, and not for parking a car, still have to comply with building code requirements for a garage?

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Here’s links to a collection of our other blog posts about STRUCTURE AND ROOMS:

Why is the grout cracking and coming loose at my floor tile?

What are the building code requirements for notching and boring holes in a wall stud? 

What causes dark or light "ghost" lines on ceilings and walls?

 Can you access or exit a bedroom through another bedroom?

What is the difference between a carport and a garage? 

What are simple ways to find the cause of a ceiling stain?

What is the minimum size of habitable rooms in a house according to the building code? 

Why is my garage ceiling sagging? 

How can I identify what kind of wood flooring I am looking at?

Why does my concrete floor slab sweat and get slippery?

What is the minimum ceiling height for rooms in a house? 

Why are there score line grooves in the concrete floor of the garage?

How much can I cut out of a floor joist? 

How can I tell if my floors are sloping?

Why do the floors slope in this old house? 

What are the common problems when a homeowner converts a garage to conditioned living space, such as a family room?

• How can I tell if a wall is load-bearing? Which walls can I take out? 

     Visit our STRUCTURE AND ROOMS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces