Entry door clearances, landings and the approach

Almost every dimension at a front door is measured to a face that is not the one people put a tape on. Clear width is not the leaf. Landing depth is not the slab. Threshold height is not the sill. Get the datum right and the code numbers turn out to be a coherent set that describes one thing: a person arriving with their hands full, in the rain, in the dark.

The four faces the numbers are measured from#

Clear width is measured with the door standing open at 90 degrees, from the face of the open leaf to the stop on the opposite jamb. It is not the leaf width, it is not the rough opening, and it is not the gap between the jambs.

Clear height is measured from the finished floor to the underside of the head stop.

Landing depth is measured in the direction of travel, so at a door in a straight wall it is the distance you walk away from the closed door face, not the width of the stoop across the opening.

Threshold height is measured from the top of the threshold, its highest point, down to the landing surface. Not to the top of the sill pan, not to the slab before the tiles went on.

Those four sentences resolve most of the arguments about entry doors. What is left is what happens when the numbers collide.

Why the code number is 32 in and the door is 36 in#

IRC R311.2 requires at least one side-hinged egress door with a clear width of not less than 32 in (813 mm) and a clear height of not less than 78 in (1,981 mm). It does not say the leaf must be 36 in wide. The leaf ends up 36 in because of subtraction.

Take a nominal 36 in leaf in a standard frame:

• Between the rebates the opening is about 35.5 in (902 mm), the leaf less the fitting gap.
• The leaf itself is 1.75 in (44 mm) thick on an exterior door, and when it stands open at 90 degrees that thickness sits inside the opening.
• The stop on the far jamb projects a further 1/2 in (13 mm).

35.5 less 1.75 less 0.5 gives 33.25 to 33.5 in (about 85 cm) of clear width. That clears the 32 in minimum by an inch and a half, and it is the only common stock leaf that does. Run the same subtraction on a 32 in leaf and you get 29.5 in (75 cm), which fails, and on a 34 in leaf you get 31.5 in (80 cm), which also fails by half an inch. Every leaf size and its rough opening is set out in exterior door sizes and standards, and the allowance over the unit is covered in rough opening sizes: a 36 x 80 in prehung exterior unit normally wants a 38 x 82.5 in (965 x 2,096 mm) opening.

The height works the same way. An 80 in leaf in a frame with a threshold gives roughly 79 in (201 cm) of clear height, one inch over the 78 in minimum. That single inch is why raising a finished floor by more than about 3/4 in (19 mm) at an existing entry door becomes a code question and not just a trimming question.

Landings, inside and out#

IRC R311.3 requires a floor or landing on each side of each exterior door. The landing must be not less than the width of the door served and must have a minimum dimension of 36 in (914 mm) measured in the direction of travel. Exterior landings may slope, but not more than 2 per cent, which is 1/4 in per foot, and the fall runs away from the door.

The 1,200 mm square in Approved Document M is the one to build to whichever country you are in. It comes out at 15.5 sq ft (1.44 m2), roughly the space a person needs to stand still, set a bag down and pull a door towards themselves. The IRC minimum of 36 in deep by 36 in wide is 9 sq ft (0.84 m2), which is a person and nothing else. Landings at internal doors and at the head of a flight follow different rules, set out in entry hall and landing sizes.

The swing arc, counted as floor area#

A door that opens at 90 degrees sweeps a quarter circle whose radius is the leaf width. For a 36 in leaf that is 3.1416 x 36 x 36 divided by four, which is 1,018 sq in, or 7.1 sq ft (0.66 m2). A 32 in leaf sweeps 5.6 sq ft (0.52 m2), and a 30 in interior door 4.9 sq ft (0.46 m2).

Two consequences follow. In a 6 x 8 ft entry hall of 48 sq ft (4.5 m2), the front door alone claims 15 per cent of the floor and a coat closet door opposite claims another 10 per cent. And that area is not merely unfurnishable, it must be clear to the floor: a rug edge, a boot tray or a floor register inside the arc will all be found by the door. The full geometry, including doors that conflict with each other, is in door swing, clearance and approach space, and the runner sizes that survive an in-swinging door are in doormat and entry runner sizes.

Manoeuvring space by approach direction#

Clear width tells you whether a body fits through. It says nothing about whether that body can get the door open. The ADA 2010 Standards handle this with manoeuvring clearances that change with the direction of approach, and they are worth applying in a private house even where they are not enforced, because they describe what it takes to open a door while holding something.

The 18 in of latch-side clearance on the pull side is the figure that gets missed, because it is not a code minimum in a house and nothing on a drawing makes its absence obvious. It is the room for your body to stand beside the door while the leaf comes past you. Put a console table, a radiator or a wall return inside that 18 in and you will back into the wall every time you come home, whatever the clear width says. The full set is in accessible door widths, hardware and approach, and the codes each figure comes from are indexed in the standards and sources reference.

The threshold and the drop to the landing#

At the required egress door, IRC R311.3.1 puts the landing not more than 1.5 in (38 mm) below the top of the threshold. At other exterior doors, R311.3.2 allows up to 7.75 in (196 mm), which is not a coincidence: it is the maximum stair riser, so a back door may effectively open onto one step, as long as the door does not swing out over it.

Accessibility standards are far tighter. The ADA caps a threshold at 1/2 in (13 mm), with anything over 1/4 in (6.4 mm) bevelled at 1:2 or shallower, and Approved Document M asks for a chamfered upstand no greater than 15 mm (5/8 in) in total. Those are the numbers to build to if the house is meant to still work in thirty years, as ageing in place dimensions argues. The profiles that achieve them are in floor transitions and threshold heights.

What changes the numbers#

Outward swinging doors. The IRC allows a landing to sit up to 7.75 in below the threshold only where the door does not swing over it. Swing the door out, common in Australia and in hurricane zones, and that concession disappears.

Storm and screen doors. These swing outwards and stack their own frame into the opening, taking about 1 in (25 mm) off the clear width. A 36 in opening that gave 33.5 in clear now gives 32.5 in, still legal with almost nothing left, and the landing has to clear the storm door's arc as well.

Sidelights and transoms. A sidelight adds 12 or 14 in (305 or 356 mm) per side to the structural opening and nothing at all to the clear width, because the fixed panel does not open. The sizes are in front door sizes and standards.

Country. A British 838 x 1,981 mm (33 x 78 in) external leaf gives roughly 780 mm (30.7 in) clear, which passes the 775 mm in Approved Document M by 5 mm and would fail the American 32 in outright. Each standard was tuned to the leaf sizes its own joinery industry already made.

Steps beyond the landing. Outdoor risers are shallower than indoor ones: 5.5 to 6.5 in (140 to 165 mm) of rise against a 13 to 15 in (330 to 380 mm) tread, as set out in garden path widths and outdoor step dimensions. The stair rise and run calculator will divide a given total drop into equal risers.

Sizing the whole approach#

Read the approach as a sequence and give each part its number.

• Path or walk: 36 in (91 cm) minimum, 48 in (122 cm) for two abreast.
• Steps: at least two risers, never one, with a handrail at four or more.
• Landing: 48 x 60 in (122 x 152 cm) is this site's working recommendation, against a 36 x 36 in code minimum and a 1,200 mm square under Part M.
• Covered head height: 80 in (203 cm) under a porch beam or a light.
• Door: 36 in leaf, 33.5 in clear.
• Inside: 18 in (46 cm) of clear wall on the latch side, and the 7.1 sq ft swing arc kept empty to the floor.

Add the inside landing to the swing arc and an entry hall needs about 30 sq ft (2.8 m2) before a single hook goes on a wall. That is why so much of entryway and mudroom planning turns out to be door geometry wearing a coat.