GuidelineRecommended
Floor surface vertical changes: 1/4 inch max vertical; 1/2 inch max with 1:2 bevel
HUD FHA Design Manual Chapter Four §4.2Description
Changes in level along an accessible route shall be limited to 1/4 inch maximum without edge treatment, or 1/2 inch maximum with a beveled edge of 1:2 slope. Greater changes require a ramp.
Why this exists
Prevents trips + wheelchair hangups. Common construction interface where door thresholds, flooring transitions, or carpet pads meet.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
maxVerticalNoBevel | max | 0.25 | in | Max vertical change without edge treatment |
maxVerticalWithBevel | max | 0.5 | in | Max vertical change with 1:2 bevel |
Categories
AccessibilityLife safety
Applies to
- When:
- aspires to visitability / universal design
Source
HUD (US Department of Housing and Urban Development)no manifest entry
Fair Housing Act Design Manual (1998 revised)
Section: Chapter Four §4.2
Published 1998-08-01 · last verified 2026-05-10
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Universal-design wider doorways · HUD UD §3.2
- Universal design features encouraged for residential accessibility under Section R320.3 · Virginia USBC 2021 Amendment 33 (IRC R320.3)
- Covered multifamily dwellings: at least one building entrance on an accessible route · HUD FHA Design Manual Requirement 1 (Chapter One)
- Public and common use areas must be readily accessible to and usable by people with disabilities · HUD FHA Design Manual Requirement 2 (Chapter Two)
- All doors must provide a clear opening of at least 32 inches when open 90 degrees · HUD FHA Design Manual Requirement 3 (Chapter Three)
Last reviewed 2026-05-10.