Crawl Spaces
From NachiWiki
The following is from the IRC as a guide ...
| R408.3 Access (for "Under-Floor Space") Access shall be provided to all under-floor spaces. Access openings through the floor shall be a minimum of 18 inches by 24 inches (457 mm x 610 mm). Openings through a perimeter wall shall be 16 inches by 24 inches (407 mm x 610 mm). When any portion of the through wall access is below grade, an areaway of not less than 16 inches by 24 inches shall be provided. The bottom of the areaway shall be below the threshold of the access opening. Through wall access openings shall not be located under a door to the residence. See M1305.1.4 for access requirements where mechanical equipment is located under floors. |
Therefore, I look for 16" of clearance from grade to framing as a minimum to enter a crawl space.
But if you don't go in you better clearly flag you didn't fully inspect the crawl space and the potential for defects, as it's usually a common problem area ... and perhaps even recommend they budget for addressing common crawl space issues until it can be fully inspected.
My general rule of thumb is that if I can fit without removing my respirator, it gets inspected.
The vast majority of modern CA homes are built on slabs - unless, of course, they're a hillside home. Most crawl spaces in CA date back to the mid '60's and earlier. That's many years of pesticide build-up, not to mention the potential for asbestos building materials.
Ventilation
The need for ventilation of crawl spaces varies widely depending on local conditions.
I personally live in a house that is 140 years old with a limestone/brick foundation basement and a 1971 addition with a crawl space with CMU. foundation. The crawl space is does not have a vapor barrier and is not ventilated. After 35 years, this non-ventilated and non vapor barriered crawl space has no evidence of excess moisture or WDO. The adjacent basement does show evidence of dryrot and sistered floor joists. The "floor" also does not have a vapor barrier and was no insulation until appx 10 years ago when I purchased it.
So what's the point? Your milage may vary with regard to ventilation requirements you are exposed to on this board. Critical factors are - local building codes, foundation drainage, soil conditions, local weather conditions etc. Be aware of what is needed where you inspect.
Here are some resources to increase your knowledge. An AIA document(PDF) which is a summarry and contains excerpts from a 88 page PATH/HUD document(link below).
Ventilation AIA 18-22-01.pdf
http://www.huduser.org/publications/..._by_design.pdf
This article was originally based on posts by Michael Larson, Jeffery R. Pope, and Robert J. O'Connor on the NACHI message board.
