Chapter 5 of the IRC® 2018 is adopted with the following modifications:

1. (1) Section R506.2.1 Fill. This section has been modified to provide fill lift measurements. This section has been modified to read: R506.2.1 Fill. Fill material shall be free of vegetation and foreign material. The fill shall be compacted in 8 to 12 inch (203 mm to 305 mm) lifts to ensure uniform support of the slab, and except where approved, the fill depths shall not exceed 48 inches (1220 mm) for clean sand or gravel and 8 inches (203 mm) for earth.

2. (2) Section R506.2.3 Vapor retarder. This section has been modified to allow for other industry accepted vapor retarders installed according to the manufacturer's specifications. This section has been modified to read: R506.2.3 Vapor retarder. A 6 mil (0.006 inch; 152 micrometers) polyethylene sheeting, other industry accepted vapor retarder products installed per manufacturer specifications or approved vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the concrete floor slab and the base course or the prepared subgrade where no base course exists. Exception: The vapor retarder is not required for the following:

   1. (A) Item 1. Garages, utility buildings and other unheated accessory structures.
   2. (B) Item 2. For unheated storage rooms having an area less than 70 square feet (6.5 square meters) and carports.
   3. (C) Item 3. Driveways, walks, patios and other flatwork not likely to be enclosed and heated at a later date.
   4. (D) Item 4. Where approved by the building official, based on local site conditions.

Amended and renumbered from 748:20-5-8 at 39 Ok Reg 2364, eff 9-14-22