A general guideline, reinforced by the Washington State Department of Agriculture, is that substructure lumber must have minimum clearances from soil. The clearances are defined as 12" from grade to the bottom of beams and 18" from grade to the bottom of joists (they rest on top of the beams.)

These clearances were not dreamed up to be mean, or to give inspectors an easy excuse to duck going in the crawl space. The fact of the matter is that, if wood is much lower than that, it is extremely difficult for workers to do any jobs in the crawl space -- plumbing, HVAC, electrical. And when wood to soil is not in the ballpark as far as clearances, it reduces potential ventilation and proper air circulation.

There is another side to it as well: If the home inspector or structural pest inspector is tenacious and tries to do the job, as best as is possible, even when clearances are tight, it can lead to pretty uncomfortable crawling.

Here is a photo of a friend, average size man, who is, like me, trying to do the best job possible in a crawl space where joists are, at no point, higher than 12" over grade and in some locations they drop down to 7" over grade.

All of this crawl space was difficult access and half of it was inaccessible -- no way to get around safely. Getting stuck is not an option.

Thanks for stopping by,

Steven L. Smith