Does the garage to house door need a fire rating?

In the US the door between an attached garage and the house does not have to be fire rated. It has to be solid and at least 1 3/8 in (35 mm) thick, or carry a 20-minute rating, and in every case it has to latch itself and close itself. The step down to the garage is governed by the stair rules, not the exterior door rules, which allows a single 7 3/4 in (196 mm) riser with no landing as long as the door swings into the house. England wants a tested 30-minute door with smoke seals, and a step with a minimum rather than a maximum. The vehicle door is a separate subject, on garage door sizes and headroom.

Three doors the IRC accepts, and only one of them is rated#

The 2021 International Residential Code, Section R302.5.1, reads in full on the door: openings between the garage and residence "shall be equipped with solid wood doors not less than 1 3/8 inches (35 mm) in thickness, solid or honeycomb-core steel doors not less than 1 3/8 inches (35 mm) thick, or 20-minute fire-rated doors. Doors shall be self-latching and equipped with a self-closing or automatic-closing device."

Three routes, and two involve no fire test.

The same section opens with an absolute: no openings from a private garage directly into a room used for sleeping purposes. No door cures it, so the garage opens into a hall, a utility room or a mudroom.

The rest of R302.5 and R302.6 covers the wall around the door: at least 1/2 in (12.7 mm) gypsum board on the garage side, 5/8 in (15.9 mm) Type X under habitable rooms above, and any duct in the garage or through the separation of No. 26 gage (0.48 mm) sheet steel with no openings into the garage. A compliant door beside a supply grille cut through the wall has not achieved the separation.

Why "fire rated" is the answer people remember#

Summaries say "fire-rated door" because the 20-minute option is the one with a name. In the sentence itself the rating is the third of three alternatives, joined by "or", and a 1 3/8 in solid-core door with a closer complies without ever having been tested. The rated door persists as the answer because a label proves itself to an inspector, while a painted solid wood door has to be shown to be solid.

Self-closing, automatic-closing and the latch#

Before 2018 the IRC required a self-closing door, which the I Dig Hardware summary describes as equipped with a closer or spring hinges. The 2018 edition added "or automatic-closing device", and the 2021 wording adds self-latching.

An automatic-closing device, in the NFPA 80 definition the article quotes, causes the door to close when activated by a fusible link or detector. That makes a hold-open closer released by a smoke detector a compliant way to leave the door open in daily use.

A spring hinge that swings the leaf to within an inch of the frame and stops has not met the rule, which asks for closing and latching. The test is whether the door, released from fully open, closes and latches without help; the Oakwood Doors guide puts the English version as closing the door fully into the frame from any normal open position.

The step is a stair, so the 7 3/4 in riser governs#

The IRC defines a stair as a change in elevation of one or more risers, so one step into the garage is a stairway and takes the stairway numbers: a maximum riser of 7 3/4 in (196 mm), measured vertically between the leading edges of adjacent treads, a minimum tread of 10 in (254 mm) where there is more than one riser, and no more than 3/8 in (9.5 mm) between the tallest and the shortest riser in a flight. Those figures are derived on stair dimensions.

Measure from the finished surface at the top of the step to the finished garage slab where your foot lands, not from subfloor to rough slab. The garage floor is laid to fall, so the height changes along the wall, and a floor finish changes it again: rubber of the kind in gym flooring thickness and sizes is 1/4 to 3/4 in (6 to 19 mm) thick and comes straight off the step. On a flight, a 3/4 in mat at the bottom alone breaks the 3/8 in (9.5 mm) limit on variation between risers.

The landing is where the door swing decides everything. Section R311.7.6 wants a floor or landing at the top and bottom of every stairway, at least as wide as the flight and 36 in (914 mm) deep in the direction of travel for a straight run. Its exception reads: a floor or landing "is not required at the top of an interior flight of stairs, including stairs in an enclosed garage, provided that a door does not swing over the stairs."

Why 1 1/2 in is quoted, and why it is the wrong rule#

The other number in circulation, 1 1/2 in (38 mm), comes from Section R311.3.1: the drop at the required egress door, or 7 3/4 in where the door does not swing over the landing. R311.3.2 allows 7 3/4 in at other exterior doors and drops the top landing for two risers or fewer outside. Both are exterior door rules, the ones dimensioned in entry door and approach clearances.

The garage door is not an exterior door. It sits between two enclosed parts of one building, and the stair section says as much by naming "stairs in an enclosed garage" in its own exception. So neither the 1 1/2 in limit nor the two-riser limit in R311.3.2 applies to it. Both sets of rules land on 7 3/4 in, which is why they are merged, and they diverge the moment a door swings the wrong way or the drop needs more than two risers.

States also edit these sections. Minnesota rewrote R311.3.2 so that no landing is needed where an exterior stairway is under 30 in (762 mm) high and the door does not swing over it. The code your building department adopted is the one that counts; the standards and codes reference lists editions.

How much garage depth the step and the swing cost#

Combine the riser and landing rules and one variable remains: the hinge side.

The treads are minimums, and the handrail becomes mandatory at four risers, so with the door swinging into the house 23 1/4 in (591 mm) is the largest drop that needs neither a landing nor a rail. Splitting a drop into equal risers is the job of the stair rise and run calculator.

Now set those depths against the garage. The planning figures on garage sizes: single, double and triple allow 24 in (61 cm) behind a car and 36 in (91 cm) in front of it, the walkway figure derived on car parking space dimensions. A door swinging into the garage over a single step spends 36 in on a raised platform before anyone has parked, and the bottom of the stair needs its own 36 in of floor, which the slab provides only while nothing is parked on it. The same hinge on the other side costs nothing: on a tight garage, reversing the door is worth a full walkway. The price moves indoors, where a 32 in (813 mm) leaf sweeps a quarter circle of that radius; clear widths per leaf are on doorway sizes.

England: E 30 Sa, a closer and a 100 mm upstand#

Approved Document B, Volume 1, sets out the English guidance. Paragraph 5.6 separates an attached or integral garage from the house with fire-resisting construction of at least REI 30. Diagram 5.1 and Table C1 ask for the door between them to achieve E 30 Sa, given in the same table as FD30S under the national BS 476-22 test: 30 minutes of integrity plus restricted smoke leakage at ambient temperature, with a self-closing device. Paragraph C5 repeats that every fire doorset between a dwellinghouse and an integral garage should be self-closing.

The step works the other way round from the US. Paragraph 5.7 says a door between the house and the garage should meet one of two conditions: the garage floor laid to fall away from the door to the outside, so fuel spills flow away, or the door opening at least 100 mm (4 in) above the garage floor. That is a minimum, set to keep liquid out, where the IRC figure is a maximum set to keep people from falling.

An FD30S rating belongs to the doorset, not the leaf. The Oakwood guide lists what makes it up: intumescent seals that expand with heat, ambient smoke seals, and the closer, installed as one assembly. A fire-rated leaf hung in an old frame with no seals has lost the rating that justified buying it. UK and US leaf sizes are compared on front door sizes and standards.

Approved Document B describes one way to comply with the Building Regulations 2010 in England, and its introduction says other ways may be agreed with building control. Rules that change at a border are collected on interior sizes by country.

When these numbers stop applying#

The IRC figures are the 2021 text as published on UpCodes from a state adoption. The 2015 edition and earlier lack the automatic-closing option, the 2018 wording quoted by I Dig Hardware has no self-latching sentence, and any state can amend the landing and riser sections. The English figures are the 2019 edition of Approved Document B with its amendments, and a house approved under an earlier edition was approved to the rules of its day. Nothing here covers glazing or openings cut into the leaf.

The hall on the house side is dimensioned in entry hall and landing dimensions, the rest of the garage numbers sit on the garage and workshop dimensions hub, and the interior unit converter checks any conversion here.