The door into the house
This is the walk-through door, not the overhead car door. The Fire Administration recommends a 20-minute fire-rated door that closes and latches by itself. The Building America Solution Center's door guide lists what the 2021 International Residential Code model code accepts for that opening:
- A solid wood door at least 1-3/8 inches thick.
- A solid or honeycomb-core steel door at least 1-3/8 inches thick.
- A door with a 20-minute fire rating.
The same guide says the door must also be self-closing and self-latching. A hollow-core interior door isn't on the list. To check yours, open it partway and let go. It should swing shut and latch without a push. If the closer is broken or disconnected, get it fixed, and don't prop the door open.
Here's the local catch. The City's building permit page says replacing doors in a one- or two-family home often doesn't need a permit, as long as the property isn't on the Philadelphia Historic Registry. That means nobody from L&I may look at a replacement garage door before it goes in. Ask the installer, in writing, which of the options above the new door meets, and whether a closer is included.
The shared wall and the ceiling
The Fire Administration calls for 1/2-inch gypsum board, or the equivalent, on a wall that attaches the garage to the house. If there's living space above the garage, it calls for a ceiling of 5/8-inch Type X gypsum board, or the equivalent, and a cover on any attic hatch in the garage. Those are reference points. Your town's adopted code and any local amendments decide what applies to your house.
Look for open holes, missing pieces of wallboard, and joints that were never taped along the shared wall and ceiling. Don't cut into anything to check what's behind it.
Holes for wires, pipes and ducts
Every opening is a path for smoke and for car exhaust. The Building America Solution Center's air sealing guide warns that open joist bays running from above the garage into living space carry carbon monoxide into the house. It also says gypsum board on those surfaces is not the same as air sealing, and that every wall and ceiling penetration needs an appropriate sealant. Its suggested checks are ones you can do with a flashlight:
- Look for cracks along the base of garage walls that adjoin the house.
- Check that every pipe, wire and duct passing through the shared wall or the ceiling below living space is sealed.
- Check whether the connecting door seals tightly when closed.
The same guide says best practice is not to put heating or cooling equipment in the garage at all. If your furnace or air handler is there, ask an HVAC contractor how its ducts and cabinet are sealed from garage air.
When an upgrade can break the separation
Insulating the shared wall can mean cutting into the protective layer. BASC's rigid foam retrofit guide starts by removing gypsum board or plaster where the garage walls and ceiling meet the shared wall, then installs a new interior finish over the foam. Before work like that starts, the written scope should say what board goes back, at what thickness, and how joints and openings will be finished.
Philadelphia generally requires a building permit for work that changes the interior of a structure or is a major repair beyond regular maintenance, while gypsum board installed over existing walls and ceilings in a one- or two-family home often doesn't need one. If you're cutting a new opening, moving a wall, or turning the garage into living space, also read our guide to zoning and building permits. New circuits or outlets in the garage are covered in our electrical permit guide.
Two cheap fixes worth doing now
The Fire Administration recommends a heat alarm, not a smoke alarm, in the garage. It sounds if the temperature rises too high. It also says to store gasoline, oil, paint, propane and varnish in a shed away from the house rather than in an attached garage. If the garage floor itself is cracking or heaving, that's a separate issue, covered in our garage floor guide.