ICC Subscriptions

R601.1 Application.
The provisions of this chapter shall control the design and construction of all walls and partitions for all buildings.

R601.2 Requirements.
Wall construction shall be capable of accommodating all loads imposed according to Section R301 and of transmitting the resulting loads to the supporting structural elements.

R601.2.1 Compressible floor-covering materials. Compressible floor-covering materials that compress more than 1/32 inch (0.8 mm) when subjected to 50 pounds (23 kg) applied over 1 inch square (645 mm) of material and are greater than 1/8 inch (3 mm) in thickness in the uncompressed state shall not extend beneath walls, partitions or columns, which are fastened to the floor.
R601.3 Vapor retarders. Class I or II vapor retarders are required on the interior side of frame walls in Zones 14 and 16. See Title 24, Part 6, Figure 101-A -California Climate Zones.


1. Basement walls.
2. Below grade portion of any wall.
3. Construction where moisture or its freezing will not damage the materials.
R601.3.1 Class III vapor retarders. Class III vapor retarders shall be permitted where any one of the following materials are used. The material options include vented cladding over fiberboard, vented cladding over gypsum, or insulated sheathing with an R value equal to or greater than R-4. If insulated sheathing is used the R-value shall be included as part of the compliance toward Title 24, Part 6 Building Energy Efficiency Standards.

Spray foam with a minimum density of 2 lb/ft3 applied to the interior cavity side of OSB, plywood, fiberboard, insulated sheathing or gypsum is deemed to meet the insulated sheathing requirement where the spray foam R-value meets or exceeds the specified insulated sheathing R-value.
R601.3.2 Material vapor retarder class. The vapor retarder class shall be based on the manufacturer's certified testing or a tested assembly.

The following shall be deemed to meet the class specified:

Class I: Sheet polyethylene, unperforated aluminum foil.

Class II: Kraft-faced fiberglass batts.

Class III: Latex or enamel paint.
R601.3.3 Minimum clear air spaces and vented openings for vented cladding. For the purposes of this section, vented cladding shall include the following minimum clear air spaces. Other openings with the equivalent vent area shall be permitted.
1. Vinyl lap or horizontal aluminum siding applied over a weather resistive barrier as specified in Table R703.4.
2. Brick veneer with a clear airspace as specified in Section R703.7.4.2.
3. Other approved vented claddings.