Accessibility and visitability are related ideas, but a familiar feature such as a step-free entrance may be a mandatory building-code requirement, a zoning or planning condition, a program requirement, or a voluntary design choice. The legal source and trigger matter. Do not assume that a requirement for an apartment building also applies to a detached ADU or a secondary suite in a house.
Identify the rule and its trigger
Ask the building official or planning authority to identify the adopted provision and whether it is triggered by the building type, number of units, storey, building area, project scope, permit date, planning permission, or a material change of use. Check whether it concerns a route into the building, interior clearances, an adaptable unit, an accessible unit, or a particular shared space. Those are not interchangeable requirements.
Jurisdiction-specific examples
In England, Approved Document M Volume 1 describes Category 1 visitable dwellings as the baseline for new dwellings unless an optional Category 2 or 3 requirement applies. The latter categories apply when the planning permission requires them. The project still needs its English building-control classification and the relevant edition; this framework does not establish a rule for Wales, Scotland, Northern Ireland, or another country. See the official Approved Document M page.
British Columbia’s adaptable-dwelling provisions illustrate why the building type and entry arrangement matter. The Province describes a one-in-five adaptability requirement in specified apartment and condominium contexts and lists exclusions such as a separate exterior entrance. That summary does not show that a detached ADU or secondary suite falls within those contexts. Confirm the current code, transition, local authority, and classification with the Province and municipality.
Ontario likewise distinguishes houses from multi-unit residential buildings in its accessibility summary. It describes a 15% basic-accessibility provision for suites in certain multi-unit buildings; that percentage should not be applied to a secondary dwelling merely because it is an additional unit. Check the current Ontario accessibility guidance and adopted code with the building department.
Visitability can also be established through zoning rather than technical code. Portland’s ADU zoning page says the condition applies on a lot with a house and two ADUs, or a lot with a duplex and one ADU: at least one unit must allow for visitors in wheelchairs. The listed features include zero-step access and entrances, bathrooms, living area, and doors. This is a local land-use example, not a universal accessibility standard; keep Portland’s zoning condition distinct from the building-code review. See Portland’s ADU zoning requirements.
Existing buildings and alternative methods
An existing-building or alternative-compliance route is not an automatic exemption. Determine whether the work is legally an alteration, conversion, extension, or new dwelling. Then ask which existing-building provisions are available, what equivalent outcome or evidence is required, and who can approve the proposed method. A conversion may trigger broader requirements than a like-for-like alteration. The reviewing authority may require drawings, a professional assessment, or inspection evidence.
What to verify before design or purchase
Record the governing code and local planning condition; the unit and building classifications; the work and permit dates; any required accessible route or adaptable-unit features; the scope of an existing-building alternative; and the professional or authority evidence needed. If a source lists an exclusion or percentage for a particular type of building, do not extend it to another type without confirmation. This page describes how to locate the applicable rule, not whether a specific design satisfies it.