A parking space can have a gentle overall slope and still contain a steeper area where someone needs to get out of a vehicle. For an accessible parking retrofit, the important question is not just how much the pavement drops from one end to the other. It is what happens within the space and its adjoining access aisle.
The federal accessibility standards allow slopes no steeper than 1:48 for parking spaces and access aisles. The U.S. Access Board explains that aisles need to be nearly level in all directions for wheelchair transfers, while allowing sufficient slope for drainage. A localized measurement plan addresses that concern better than a single overall slope.
The slope limit is not an average-slope allowance
An access aisle is the designated area beside an accessible parking space where people using wheelchairs or other mobility devices get into and out of vehicles. ADA.gov describes the parking-space slope limit as 1:48, approximately 2.08%, in all directions. The Access Board also requires access aisles to be at the same level as the parking spaces they serve, with changes in level prohibited.
Those provisions are not an invitation to average a steep area together with a flatter one. A favorable end-to-end result alone does not establish that the intervening surface meets the limit in all directions.
This is general federal guidance, not a property-specific compliance determination. Requirements vary by state and jurisdiction. Before finalizing a retrofit, confirm applicable state and local requirements with your county or other permitting authority and a licensed professional familiar with accessibility requirements.
An illustrative retrofit: a rise hidden by the average
Imagine an owner planning to relocate an accessible space near a building entrance. This is a hypothetical example, not a surveyed property. The proposed parking area looks fairly flat, and a comparison between its far ends suggests a gentle slope.
Now suppose a localized rise crosses part of the proposed access aisle. The pavement climbs toward that rise and then falls away. Comparing only the distant endpoints would not describe either side of it. The overall result could look acceptable while a shorter section is steeper than the permitted slope.
To examine that possibility, request spot elevations—pavement heights measured at identified locations—within the proposed layout. Ask for nearby measurements around the rise rather than relying only on the outside corners. The review question becomes specific: what slopes occur where the proposed space and aisle will actually sit?
Include the connection to the entrance
ADA guidance says that accessible spaces added to an existing lot should be on the most level ground close to the accessible entrance, and an accessible route must connect the parking to that entrance. A convenient parking location therefore needs more than a favorable slope result inside the painted lines.
The Access Board specifically explains that built-up curb ramps cannot project into parking spaces or access aisles because they would create slopes greater than 1:48. Include that connection in the review rather than leaving it as a separate problem to solve after striping.
What to request before review or repair pricing
Ask for a measurement proposal that addresses the proposed layout, not simply a general description of the lot. The following is a suggested project scope, not a federally prescribed measurement procedure:
- Show the proposed boundaries. Identify the parking space, access aisle, and connection to the entrance route on the same drawing.
- Use a common elevation reference. Request identified pavement heights referenced consistently so the reviewer can compare nearby points.
- Include interior measurements. Ask the measurement professional to address visible rises, depressions, and changes in pavement slope within the space and aisle, not only their corners.
- Show localized slope checks. Request the locations and directions of checks, with the elevation differences and distances used, rather than one overall slope label.
- Document limitations. Ask which areas were checked, which could not be measured, and whether additional measurements are recommended before design decisions.
Agree on the measurement approach with the accessibility reviewer before fieldwork. The sources discussed here do not establish a required point spacing or instrument for these checks; ask the professionals involved to define an appropriate scope.
Give the contractor a defined repair question
For the hypothetical aisle with a localized rise, ask the reviewer to identify the area needing further evaluation and the intended relationship to surrounding pavement. Then request pricing against a defined repair scope rather than asking a contractor to “make the accessible parking compliant” without a plan.
Before authorizing striping or pavement work, have the accessibility professional review the proposed layout, localized measurements, and entrance connection together. Resolve the questionable areas before accepting a reassuring average as the answer.
Featured image: Image by MabelAmber from Pixabay (Pixabay Content License)
Footnotes & Sources
- U.S. Access Board – ADA Accessibility Standards, access-board.gov. — Parking-space and access-aisle surface provisions, the 1:48 slope exception, wheelchair-transfer and drainage rationale, and restrictions on projecting built-up curb ramps.
- Accessible Parking Spaces, ADA.gov, July 29, 2026. — Purpose of access aisles and the parking-space slope limit of 1:48, approximately 2.08%, in all directions.
- ADA Compliance Brief: Restriping Parking Spaces, ADA.gov, July 29, 2026. — Guidance to locate added accessible parking on the most level ground near an accessible entrance and provide an accessible route to that entrance.