How to Measure Clear Width and Gain It Without Widening

Why this matters

"The door is 32 inches, so the wheelchair fits" is the most common wrong measurement in accessibility work. The 32 inches is the slab. The wheelchair cares about the space between the open door and the far stop, which is usually about 2 inches less, and about whether the chair can make the turn to reach the door in the first place. Get it wrong one way and the shop quotes a wall-and-header job the house did not need. Get it wrong the other way and the person's knuckles take the paint off the jamb every day, or they cannot get into the bathroom at all.

Clear width versus slab width

• Slab width is the door's nominal size: a "2/8" door is a 32-inch slab, a "3/0" is 36 inches.
• Clear width is what a person passes through. The 2010 ADA Standards use a minimum of 32 inches of clear width (404.2.3), measured with a swinging door open 90 degrees, from the face of the door to the stop on the opposite jamb. In a private home that number is a reference, not a requirement; the right number is set by the person's mobility aid.

The same section allows door hardware between 34 and 80 inches above the floor to project up to 4 inches into the clear width, and allows no projection below 34 inches, which is the zone wheels and hands use.

  PLAN VIEW, LOOKING DOWN, DOOR OPEN 90 DEG

  wall ====+                          +==== wall
      hinge|                     stop |latch
      jamb |##                      ] |jamb
           |##<--- clear width ---->] |
           |##                      ] |
           +##                        +
            ##  door slab, open, its
            ##  thickness sits inside
            ##  the opening

What eats the difference between slab and clear: the door's own thickness and hinge knuckle on one side, the stop on the other. That is why a 32-inch slab typically gives about 30 inches clear, and why the options below work by moving the door out of the opening or taking the stop away.

The steps

1. Measure the person's aid, in use. Measure the wheelchair, walker or scooter at its widest point, then watch the person go through a doorway they already use. A self-propelled manual chair user's hands sit outside the wheels; measure from knuckle to knuckle while they push, not the chair alone. Skip this and you size to a brochure number, and the person's hands find the jamb.

2. Measure clear width the way the reference does. Open the door to 90 degrees, hold it there, and measure from the door face to the stop on the latch side, at about 30 inches above the floor where the hand rim sits, and again at the narrowest point if the jamb is out of plumb. Record the slab width and the jamb's inside width too. Skip this and the quote is built on the slab number, which flatters every door by about 2 inches.

3. Check how the person reaches the door. A head-on approach needs the least width. A door off the side of a hallway needs the chair to turn 90 degrees between walls, and that turn often decides the job, not the door. The 2010 ADA Standards use a 36-inch clear width for an accessible route (403.5.1) and add maneuvering clearance at the door, including 18 inches beside the latch on the pull side (404.2.4) - all reference numbers in a home. The useful test is a mock-up: tape the door opening's width on the floor of an open room, tape the hallway walls, and have the person try the turn at their own pace with someone walking beside them, stopping at the first contact. Skip this and a door that measures right still cannot be reached.

4. Pick the least invasive option that delivers the width. Work down this list and stop at the first one that gets the measured need:

• Offset hinges (also called swing-clear hinges) replace the standard hinges and swing the door out past the hinge jamb as it opens, so the slab no longer sits in the opening. The gain is roughly the door's thickness plus the knuckle, commonly 1.5 to 2 inches; measure after. The door needs room to open past 90 degrees without hitting a wall.
• Removing a stop gains the stop's thickness, often about half an inch, where the stop is the limiting element. With offset hinges fitted, the stops on both jambs may now be the limits. A door needs a stop to close against, so this usually means a thinner stop rather than none.
• Removing the door entirely gives jamb-to-jamb width and ends the swing in a tight room. It costs privacy and sound, which a curtain or a surface-mounted panel can partly restore.
• A surface-mounted sliding (barn-style) door hangs on a track over the wall beside the opening. Clear width is close to the full opening, nothing goes into the wall, and it needs a stretch of clear wall beside the opening as wide as the door. It does not seal well for sound or smell.
• A pocket door slides into the wall and gives nearly full opening width, but it means opening the wall beside the door, which must be free of wires, pipes and ducts and, if the wall is bearing, needs a header. Its flush pulls need a pinch grip, which defeats the purpose for many users; fit a pull a closed hand can work (see related: Lever Handles and Controls a Hand Can Work).
• Reversing the swing does not add clear width, but a bathroom door that swings out frees the floor space a chair needs inside the room.

Skip the ordering and you open a wall to gain an inch a pair of hinges would have delivered.

5. Re-measure and test with the person. Measure clear width again after the change, then repeat the step 3 trial at the real door, slowly, with someone beside the person and the door held open. Stop at the first contact and do not push the chair through by hand. Skip this and you deliver a number instead of a doorway.

6. Record what you measured and what you chose. Slab, jamb width, clear width before and after, the aid's width in use, the approach, and the option used. Skip this and the next contractor measures the slab and starts over.

Hazards inside the steps

• Paint on old trim. Pulling stops and casings in a pre-1978 house disturbs paint that may contain lead. Small jobs may fall under the minor-repair exemption in EPA's Renovation, Repair and Painting Rule (40 CFR 745), but mist before prying, do not dry-sand, and HEPA vacuum the debris.
• Lifting doors off hinges. A solid-core slab is heavy and awkward; two people lift it, and the hinge pins come out with the door supported, not hanging.
• Opening a wall for a pocket door. Treat every wall as live until proved otherwise: shut off and lock the circuit, and prove it dead on a known live source before and after (NFPA 70E Article 120 (120.5 in the 2021 edition, renumbered in 2024), with work practices at 29 CFR 1910.333(b)(2)), or hand the electrical part to an electrician. A bearing wall goes to a sibling procedure. See related: How to Widen a Doorway in a Bearing Wall Safely.

Worked example: two doors, two answers

A man who uses a self-propelled manual wheelchair is moving back home. Measured in use, his knuckles while pushing span 27 inches. His bedroom door is at the end of the hallway, approached head-on. His bathroom door opens off the side of a 36-inch hallway.

Bedroom: 32-inch slab. Measured clear width with the door at 90 degrees: 30.0 inches. Against his 27 inches that leaves 1.5 inches each side, which a head-on approach usually handles, but he catches the hinge-side door edge now and then. Offset hinges go on, and the re-measure reads 31.5 inches clear, a gain of 1.5 inches (31.5 minus 30.0). He passes through in the trial without contact. About an hour of work, no wall touched.

Bathroom: 28-inch slab. Measured clear: 26.0 inches, which is 1 inch less than his hands (27 minus 26). Offset hinges would add perhaps 1.5 to 2 inches, so roughly 27.5 to 28 inches. Removing the door entirely gives the jamb's inside width, measured at 28.25 inches. On paper both options just clear 27 inches.

The turn says otherwise. In the taped mock-up of the 36-inch hallway and a 28-inch opening, he cannot swing the chair's front casters into the opening without his footrest striking the far wall line, and he tries three times. A head-on door at 28 inches would work; this one, reached by a 90-degree turn from a 36-inch hall, does not.

The answer. For the bathroom, nothing short of widening delivers what the turn needs. The shop quotes a widened opening for a 36-inch slab with offset hinges, and checks whether the wall is bearing before quoting the method. Meanwhile, as a stopgap while the work is scheduled, the bathroom door comes off and a curtain goes up, which gives him 28.25 inches with no door slab to clear. In the mock-up he manages the turn backing in, which some chair users find easier through a tight turn, though he dislikes it as a daily method.

What would have changed the answer. If the bathroom door had faced down the hallway, the 28.25 inches jamb-to-jamb would have served with no carpentry. If the hallway were 42 inches rather than 36, the turn into a 28-inch opening might have worked; the mock-up decides, not a rule of thumb. If he had used a power chair, which cannot back and fill as easily, even the bedroom answer might need re-testing.

The failure mode. Measuring the bathroom's 28-inch slab against his 27-inch chair, calling it close, and fitting offset hinges. The number would have read about 28 inches, and he still would not have made the turn.

References

• 2010 ADA Standards for Accessible Design, 403.5.1 (clear width of route), 404.2.3 (door clear width) and 404.2.4 (maneuvering clearances), used as a dimensional reference in a private home
• EPA Renovation, Repair and Painting Rule, 40 CFR 745
• NFPA 70E Article 120 (120.5 in the 2021 edition, renumbered in 2024); 29 CFR 1910.333(b)(2)
• See related: How to Widen a Doorway in a Bearing Wall Safely; The Accessibility Walkthrough With the Person Who Lives There; Bathroom Layout for a Wheelchair User