Doorway clear width, thresholds and turning space: measuring a home for a mobility aid

Which standards give the figures, and do they apply to a private home?

Four Canadian documents supply the numbers in this article, and each was written for a different kind of building. The National Building Code of Canada 2020 (NBC) sets barrier-free requirements in Section 3.8 for buildings that fall under Part 3, which means public, commercial and larger residential buildings; the provinces and territories adopt it with amendments, and Ontario, British Columbia, Alberta and Quebec publish their own editions (source 1). CSA/ASC B651:23, Accessible design for the built environment, published in January 2023, is the national standard most codes point to for the details, and it covers buildings and exterior spaces rather than houses (source 2). CSA/ASC B652:23, Accessible dwellings, also from January 2023, is the first national standard written for the design of new homes and for alterations to existing housing, and its figures are the closest thing an OT has to a residential reference (source 3). CAN/ASC-2.8:2025, Accessible-Ready Housing, published by Accessibility Standards Canada in May 2025, describes a home built so that it can be adapted later with little structural work; it leans on B652 for door widths and repeats the same clearance figures (source 4).

Houses and small buildings are governed by Part 9 of the code, which has never required a barrier-free path of travel inside a dwelling. A proposed change to NBC 2020 (change 1884, under public review in 2024) would add a minimum set of accessibility features to Part 9 dwellings for the first time: doorways with a clear width of at least 850 mm, thresholds no higher than 13 mm and bevelled, and a path of travel at least 1000 mm wide from the entrance to the living, dining and washroom areas on the entrance level (source 5). Until a province adopts something like it, the standards remain voluntary for a private home. What they offer the OT is a defensible number: when a report says a bathroom door has a clear width of 700 mm against a residential reference of 860 mm, the contractor knows how much has to change and the funder knows why.

The need is not small. Statistics Canada's 2022 survey found that 10.6% of Canadians aged 15 and over, more than 3.1 million people, had a mobility disability, and that 52% of them used adapted features in their home, most often bathroom aids (38%), walk-in tubs or showers (20%), and ramps, ground-level entrances or lifts (9% each) (source 6). Every one of those features begins with a measurement that someone had to take correctly.

How wide does a doorway need to be for a wheelchair?

The code figure is 850 mm. NBC 2020 article 3.8.3.6(2) reads: "Doorways in a barrier-free path of travel shall have a clear width not less than 850 mm when the door is in the open position" (source 1). That is an increase from the 800 mm in NBC 2015, made "to limit the probability that persons using a wheeled mobility device will have difficulty in negotiating through the door opening without hitting the frame" (source 7). The residential standard asks for slightly more: B652 clause 5.7.1 sets a minimum clear opening of 860 mm for a swinging door measured at the 90 degree open position, and the same 860 mm for a sliding door (source 3). CMHC's visitability fact sheet, which is older and aimed at builders, gives 810 mm as the minimum, 860 mm as preferable and a 915 mm door as the comfortable standard (source 8). For clients in the United States, the ADA Standards set 815 mm (32 in.) at section 404.2.3 (source 9).

The figure that matters is clear width, and clear width is smaller than any number printed on a door or a frame. It is measured with the door open to 90 degrees, from the face of the door to the stop on the opposite jamb (source 7, source 9). The door slab, its hinges and the stop all take space out of the opening, so a frame that reads 810 mm between the jambs will not give 810 mm of passage. Measure at the narrowest point, which is usually at the height of the door handle rather than the floor, and record the swing direction and which side the hinges are on, because the fix depends on both.

When a doorway is short of the reference, the report should say by how much, since the remedies are graded. A door that is a few centimetres short can often be brought within range by swing-clear (offset) hinges, which carry the open door out of the opening, or by removing the door and the stop where privacy allows. Anything larger means the frame moves, which is contractor work and, in a load-bearing wall, engineering work. The funding programs guide covers which payers accept a doorway widening and what they want to see on the form.

How high can a threshold be?

Thirteen millimetres, and the shape of the edge matters as much as the height. NBC 2020 article 3.8.3.6(5) states that the threshold for a doorway in a barrier-free path of travel "shall not be more than 13 mm high" (source 1). CSA B651 (Table 4) and B652 (Table 2) grade the edge: a change in level up to 6 mm may be vertical; between 7 mm and 13 mm it must be bevelled at a slope no steeper than 1:2; above 13 mm the standards treat it as a ramp, at no steeper than 1:12, and B652 stops that allowance at 50 mm (source 2, source 3). The ADA rule is the same shape in inches: a half inch maximum, bevelled above a quarter inch (source 9). The change proposed for Part 9 dwellings expects the 13 mm limit to add nothing measurable to construction cost while removing a trip hazard (source 5).

Measure the height of the threshold from the finished floor on each side of the door, because they are rarely the same, and note the material of the floor the wheel lands on. An exterior door often has a raised sill that the client steps over without noticing until the walker catches it, and a sliding patio door has a track that a manual chair cannot cross in either direction. Inside the home the usual offenders are the transition strips between flooring types and the raised lip at a bathroom door. A threshold ramp is a small purchase that many programs will fund on the strength of one measurement, provided the report gives the height and the width of the opening it has to span.

How much room does a wheelchair need to turn?

The code asks for a circle 1700 mm across, or a T-shaped space of equivalent reach, wherever a barrier-free path ends in a confined width (NBC 2020 article 3.8.3.2, source 1). The residential standard asks for 1800 mm in new construction, with a T-turn of 1800 mm by 1200 mm by 1200 mm as the alternative, and requires an 1800 mm turning space in the bathroom (B652 clauses 4.4.2 and 5.9.2, source 3). CAN/ASC-2.8 repeats the 1800 mm diameter and the same T-turn (source 4). B651 gives 2100 mm by 2100 mm for a U-turn by a larger powered chair, and B652 notes that a scooter may need a diameter of 3150 mm (source 2, source 3). CMHC's older figures for a bathroom are a 1500 mm by 1500 mm turning circle for a manual chair and 1800 mm by 1800 mm for a power wheelchair or scooter, with 750 mm by 1200 mm of manoeuvring space in front of or beside every fixture (source 8).

Two other clearances go with the turning circle. The first is the clear floor space for a wheelchair that is stationary, which is 820 mm by 1390 mm in B651, B652 and CAN/ASC-2.8 alike, and is the space a client needs beside a bed, in front of a sink or at a transfer point (source 2, source 3, source 4). The second is headroom, which is rarely a problem above ground but is set at 2030 mm along a path of travel in a basement by CAN/ASC-2.8 (source 4).

Turning space is the measurement most often left out of a home assessment report, partly because a tape measure gives a line and the standard asks for a circle. The working method is to measure the largest clear rectangle in the room at floor level, with the door in the position the client will use it, and then to name what intrudes: the toilet bowl, the vanity, the radiator, the swing of the door. A bathroom that is 1500 mm wide between the tub and the vanity has no 1700 mm circle whatever its length, and the report should say so plainly rather than list the dimensions and leave the reader to work it out. Knee space under a sink counts toward a forward approach but not toward a turn, so record it separately.

What about hallways, landings and the space beside the door?

A doorway is only usable if the client can get to it and open it. The code's unobstructed width for a barrier-free path of travel is 1000 mm outside of doorways (NBC 2020 article 3.8.3.2, source 1). B652 sets interior paths at 1200 mm and exterior paths at 1500 mm for new homes, and allows 1000 mm for alterations to an existing one (source 3). CAN/ASC-2.8 uses the same 1200 mm and 1500 mm and allows a short pinch of up to 600 mm in length to narrow to 860 mm (source 4). CMHC's visitability figure for a hallway is 1100 mm (source 8). Measure the narrowest point of every corridor the client uses, not the nominal width, and note what makes it narrow; a hall table and a radiator are cheaper to move than a wall.

Beside the door, a person in a wheelchair needs room to reach the handle and pull the door past the footrests. NBC 2020 article 3.8.3.6(11) requires a clear space on the latch side of at least 600 mm beyond the edge of the opening where the door swings toward the person, and 300 mm where it swings away (source 1). CAN/ASC-2.8 repeats those figures and adds 300 mm on each side of a sliding door, with the manoeuvring area at least 1200 mm deep inside and 1500 mm outside (source 4). The ADA figures are 18 in. and 12 in. respectively (source 9). At the front door, CMHC recommends a landing of at least 1500 mm by 1500 mm, and the code sets the ramp slope at no steeper than 1:12 (NBC 2020 article 3.8.3.5), which is why the total rise of the entrance steps is the number that decides whether a ramp will fit on the lot (source 1, source 8).

How should the measurements appear in the report?

Each measurement needs a location, a number, a unit and the reference it was checked against, in that order, and the report should use one unit throughout. "Main bathroom door, clear width 690 mm with the door open to 90 degrees, hinges on the right, swings out; residential reference 860 mm (CSA/ASC B652)" tells the contractor what to build and tells the funder that the recommendation rests on a standard rather than a preference. A photograph of each doorway and threshold, taken square on with the tape in frame, saves the return visit that a missing number usually causes. The report writing guide has the full room-by-room list; this article covers the four measurements that most often decide whether a client stays home.

Say which figure you used and why. A manual chair user with good upper-body strength may manage a doorway at 800 mm; a power chair or scooter user will not manage the 1500 mm bathroom circle that CMHC once described as basic. The standard supplies the ceiling and the floor, and the OT's assessment of this client, this chair and this home supplies the recommendation. That is the clinical decision, and the report should read as one.

The four measurements, in one list

1. Every doorway on the client's route: clear width with the door open to 90 degrees, from the face of the door to the stop; swing direction; hinge side. Reference 850 mm (NBC 2020) or 860 mm (CSA/ASC B652).
2. Every threshold and change in floor level: height from the finished floor on each side; whether the edge is vertical, bevelled or ramped. Reference 13 mm, bevelled above 6 mm.
3. Latch-side clearance at each door: 600 mm where the door swings toward the client, 300 mm where it swings away; 300 mm each side of a sliding door.
4. Every hallway: width at the narrowest point and what makes it narrow. Reference 1000 mm (NBC 2020), 1100 mm (CMHC), 1200 mm (CSA/ASC B652 new construction).
5. Bathroom, bedroom and kitchen: the largest clear rectangle at floor level and whether a 1700 mm or 1800 mm circle fits; 820 mm by 1390 mm beside the bed and in front of the sink and toilet; what intrudes.
6. Entrance: number of steps and total rise, landing size (reference 1500 mm by 1500 mm), sill height, handrails.

Common questions