Diagonal Parking Dimensions

Diagonal striped accessible parking stall.In order for a parking stall to be considered “accessible”, it must meet a few specific requirements. The main requirements include the length, width, surface slope, striping, width of access aisle and signage. No matter the configuration of the stall, the angle of the stall in relation to the drive aisle, all of the same requirements must be met. Being compliant is fairly straightforward (pun intended) if the stall are at 90-degrees. When the stalls are provided at an angle, we call them “diagonal stalls”, the minimum requirements of dimensions get very hard to meet.

Dimensions for van accessible parking stall

Minimum Accessible Stall Dimensions

Here is a sketch of the most basic, “straight in” or “perpendicular” accessible stall. The current CBC code requires the length of the stall to be 18-feet long (216 inches) and 9-feet (108 inches) wide (CBC 11B-502.2). The code requires an access aisle immediately adjacent to the stall and for ADA, “the length of the access aisle must be the same length as the stall”, and for CBC, “it must be the same length and no less than 18-feet.”Let’s “group” the stall and access aisle together into one big rectangle that is a minimum of 18-feet long and 13-feet wide. If you’re dealing with a “Van” stall, the rectangle would need to be 18-feet long and 17-feet wide. This large rectangle (shown in a red outline) is technically what will need to meet the surface slope requirement.

Dimensions for van stall including access aisle

Stall and Access Aisle Together

Let’s “group” the stall and access aisle together into one big rectangle that is a minimum of 18-feet long and 13-feet wide. If you’re dealing with a “Van” stall, the rectangle would need to be 18-feet long and 17-feet wide. This large rectangle (shown in a red outline) is technically what will need to provided, no matter the orientation, at a surface slope less than 2% (1:48).

In existing parking lots with diagonal stalls, most standard stalls are 19 feet long.  This is typically measured from the end of one stripe to the end of the adjacent stripe.  This layout provides a standard parking stall with a minimum length of 19 feet, even in the diagonal configuration.  If an accessible van stall is included in this standard configuration, you can see that the provided rectangle including the stall and access aisle is effectively only 14.4 feet long, much less than the 18 feet required.Van stall rotated 30 degrees

Here are sketches showing the “progression” from a 90-degree stall to a 45-degree diagonal stall, with our minimum rectangle needed to be accessible.

Correct dimensions for 60 degree van stall

Correct dimensions for 45 degree rotated van stall

For parking lot designers, the equivalent depth from the curb to the edge of the drive aisle typically drives (another awesome pun) the design to meet site requirements.  Each local building department may have it’s own minimum requirements for drive aisles based on the angle of parking stalls.  For our example, let’s say that if the parking stalls are at 90-degrees, the minimum required drive aisle between stall striping on both sides is 27-feet.  Furthermore, if the parking stalls are at 45-degrees, the minimum width will be 12-feet to allow one-way circulation.

For parking lot designers, the equivalent depth from the curb to the edge of the drive aisle typically drives (another awesome pun) the design to meet site requirements.  Each local building department may have it’s own minimum requirements for drive aisles based on the angle of parking stalls.  For our example, let’s say that if the parking stalls are at 90-degrees, the minimum required drive aisle between stall striping on both sides is 27-feet.  Furthermore, if the parking stalls are at 45-degrees, the minimum width will be 12-feet to allow one-way circulation.

Once we start designing diagonal parking stalls and incorporate accessible stalls at a diagonal, the dimensions don’t work out so well.  Remember, we need to keep our “accessible rectangle” free of any obstructions and out of the drive aisle.  Here is how diagonal stalls would look on our site with an accessible van stall.  After we rotate our accessible rectangle 45-degrees, the effective depth of the stalls from the curb face to the end of striping will be 24.75 feet, this reduces the drive aisle from 12 feet to just over 7 feet wide!

reduced aisle width with 45 degree rotated van stall

Due to the requirement for the stall and the access aisle to be adjacent for the full length, diagonal stalls cause a large challenge to designing a parking lot.  If you have an existing parking lot with diagonal stalls, and are looking to improve your accessible stalls to meet current codes, you will most likely not have the physical room to upgrade your stall.

David HornDiagonal Parking Dimensions