3.1402.5 Closed Crawl Spaces—Attached Crawl Spaces Under Unconditioned Spaces

Topic: 
Basements and Crawl Spaces
Subtopic: 
Crawl Spaces
Desired Outcome: 
Closed, attached crawl spaces sealed but accessible
TitleSpecification(s)Objective(s)
3.1402.5a
Separate crawl spaces

A continuous air and vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1 between the attached crawl space under unconditioned spaces and the closed crawl space Closed crawl space A foundation without wall vents that uses air-sealed walls, ground and foundation moisture control, and mechanical drying methods to control crawl space moisture. Insulation may be located at the conditioned floor level or on the exterior walls. Return pathways are not allowed from the crawl space to the living space will be maintained

Prevent air and moisture penetration

3.1402.5b
Entry point

When adding access to a crawl space:

Access openings through the floor will be a minimum of 18 inches by 24 inches or as constrained by existing framing members

Openings through a perimeter wall will be not less than 16 inches by 24 inches or as constrained by existing framing members

When any portion of the through-wall access is below grade, an area way not less than 16 inches by 24 inches will be provided

Under-floor spaces containing appliances will be provided with an unobstructed access large enough to remove the largest appliance but not less than 30 inches high and 22 inches wide or more than 20 feet long measured along the center line of the passageway from the opening to the appliance

A level service space at least 30 inches deep and 30 inches wide will be present at the front or service side of the appliance

If the depth of the passageway or the service space exceeds 12 inches below the adjoining grade, the walls of the passageway will be lined with concrete or masonry extending 4 inches above the adjoining grade in accordance with Chapter 4 IRC IRC International Residential Code

The rough-framed access opening dimensions will be a minimum of 22 inches by 30 inches and large enough to remove the largest appliance

Provide access to attached crawl space for inspections