I’m building a new detached garage/workshop. One half will have a concrete floor and the other half will have a wood floor over a 24″ deep crawlspace. I’ve poured a concrete footing below frostline and laid up four courses of concrete block. The exterior of the block foundation has been coated with waterproofing sealer up to the grade line.
My question for more experienced builders is this.. Can I leave the exposed ground in the crawl space without experiencing moisture problems? This area will be below my workshop filled with tools, equipment and other toys. I don’t want to waste money nor do I want to live with a bad decision. Any advice is greatly appreciated.
Replies
No. Vapor barrier (8 mil min.) + crushed stone, minimum, 4" slab on top better.
T. Jeffery Clarke
You'll also want to consider the ventilation issue for the crawl space. The answer depends on your climate and soils and heating system.
In my area (NW Ohio) conditioned crawlspaces (vapor retarder on soil, insulated walls and a forced air heat register) seem to be the best avenue to a dry and mold free crawl space (and mold free attic, as well!.)
Differernt regions have different needs.
By the book
1) perimeter drain if crawl grade is more than 1' below exterior grade, drain is not required when foundation is on well drained soil ( group I soils )
2) exterior grade falls 6" in 10' away from bldg or 3" in 6' if site conditions are tight
3) grade crawl to drain that penetrates foundation wall or to bottom of access door
4) (if no vapor barrier) min 1 sqft ventilation opening for every 150 sqft of under floor space,one such vent opening to be within 3' of each corner
5) (if 6 mil vapor barrier) may reduce openings to 1 sqft opening to 1500 sqft of under floor space
While this is code, the bottom line is moisture content in soil varies from site to site. You will have to see if it will be dry enough for storage.