Crawl Space
Crawl Space https://codes.iccsafe.org/content/NCRC2018/chapter-4-foundations
Crawl spaces can be vented or unvented. Vented crawl spaces are less like to have mold and mildew problems; therefore we will have a vented crawl space.
Even though we will be following the regulations for a vented crawl space, we are allowed to use vent covers at our discretion, for example in the winter time. Because at times our crawl space may be functionally non-vented, we will provide an electrical outlet in the crawl space for a dehumidifier.
A vapor barrier will be placed on the ground as that reduces the required amount of venting that is required.
R408.1 Crawl Space Ventilation
A square foot of ventilation opening is required for every 1500 square feet if a class 1 vapor barrier is used. The typical foundation vent is 16”x8”, the size of a cement block, thus requiring at least a square ft of total venting is not a problem, as long as a ground vapor barrier is used.
One vent opening shall be within 3 ft of each corner. Thus at least 8 vents are required which greatly exceeds the requirement for vent size. We will use 8 vents.
To prevent pests from entering through a vent, the vent holes must not exceed 1/4” in any direction. Grills or other vent overs may be used if the vent itself has openings that are too large.
No drain, for example from a heat pump, may discharge into the crawl space.
R480.2 Ground vapor barrier
Rake surface smooth for easier installation
Use at least 6 mil thick vapor barrier
Cover all exposed earth Overlap the vapor barrier edges by at least 12”
The NC requirements do not mention taping the seams (I think the international requirements do). We will not tape the seams.
Home Depot $148 20 ft. x 100 ft. Black 6 mil Plastic Sheeting
Model #CFHD0620B
R408.3 Wall Damp Proofing
Where the finished grade is higher than the inside grade, the exterior walls must be damp-proofed from the top of the footing to the finished grade.
R408.8 Access
Minimum size access panel is 18” x 24”. Since our floor joints will be 16” on center this requires us to create a space using headers that will be approximately 32” wide.
R408.9 Removal of debris
“The crawl space floor shall be cleaned of all vegetation and organic material”. TBD - verify that we is OK to cover grass with the plastic vapor barrier. The intent of the above requirement is probably to make sure leaves, pieces of wood, etc are not left in the crawlspace to attracter termites.
R408.10 Finished grade.
Since our site is dry, the finished grade of the crawl space can be at the bottom of the footings.