quote from the “structural issues for home inspectors course” regarding clearances of joists and beams under a crawlspace.
“The grade (soil) should be at least 18 inches below the bottom of the floor joists, and 12 inches below beams. However, some codes require 24 inches below the bottom of the floor joists and 18 inches below the beams so that inspectors and contractors can enter. Most codes require 18-inch-high access openings. So, if a beam is lower than that, the inspector should note it in his report as a restriction. Columns and posts must be constrained to their footings, must be a minimum of 4x4, must be connected to girders with approved hardware,…”
according to the first sentence, a joist should be 18in above grade and a beam 12in above grade. Then later in the paragraph it says any beam below 18in should be reported. Which is the correct measurement? if it is 18in then why even mention 12in?!
and if the correct measurement is 18in for beams, then should i look for 24in high joists?
Additionally, it mentions that columns must be attached to their girders; are girders the same as beams? most columns i see in pictures are supporting a beam running parallel to floor joists. Some clarification on this would be awesome, thanks!
Definitely a poorly worded section IMO. The crawl space opening dimension is also incorrect. 18" X 24" is for floor openings. 16"X24" is minimum for vertical openings (like a window into the crawl space).
The problem with a lot of these definite lengths, etc. is most of this is new code and you’ll find houses built across the last 125+ years. Then, factor in regional differences and it’s virtually impossible to apply a “one-size-fits-all” system. Historically, for things like FHA/VA loans I’ve heard the 18" under joists, 12" under beams thing and that is generally what I inspect to. But I also call it out when mechanical items restrict access. It’s super common in my area to have rigid heating ducts that are just beat to hell from every telephone repairman and cable guy that has forced their was through the crawl space. Then someone has the bright idea to insulate everything and you’ll never get into the space.
Obviously for the test you need numbers and I’d go with 18" and 12". In practice there’s a lot more to it than just using a ruler.
Here is a graphic. I pretty much follow this regardless if the beam is wood or steel. I am not a code inspector, therefore I use “best practice” and recommend correction where applicable.