These kinds of things are different everywhere. I can comment on the termite pretreatment, though. (We are pest control operators with experience in CA and OR). They are normally optional and I find contractors woefully ignorant on this issue; it's not even on their radar.

Are you saying he built your addition on top of an existing slab? Then, yes, you can't treat your sub area, but you are also less likely to have a problem as long as you don't have a moisture issue. Treatment for subterranean termites can be done by injection on a slab patio/pathway around the outside of your addition, or by trenching. I would not drill into your foundation.

What is the clearance? Here, clearance should be about 18" from bottom of floor joist to ground or 12" from bottom of girder to ground. There should be some kind of access available to get in there and there should be vents. Any laundry venting should be outside the building. Please make them build you an access, and I'd also consider crawlspace encapsulation at some point.

Lots of things have been done wrong @krismays... It's not exactly a slab, but it's an old slab and stone patio that was cracked and had moss in it, and he poured concrete on top of the parts that had moss, grass or dirt. So we THINK it's only concrete under there. The one expert is saying that termites can find their way in the cracks of concrete and that the area is going to get humid... There's no venting to the outside, though there's venting into our basement. There's only a couple inches between the base of the floor joist and the concrete so you can access anything other than tearing up the hardwood floors of our addition... he even left in the wood forms, even after I asked several times if they should be removed. And the city inspectors had no problem with it since "it's all concrete..." I feel like we're just asking for trouble...

Will see if they can get under the addition w/out drilling? My hubby is really worried about drilling into the foundation... Thanks for the info!

This is a link to the IRC pertaining to additions. https://www.iccsafe.org/cs/codes/Documents/2007-08cycle/FAA/IRC-RB2-RB105.pdf

With attention to Table R302.1 in your particular instance http://publicecodes.cyberregs.com/st/ca/st/b400v10/st_ca_st_b400v10_3_sec003.htm

As a note in a high humidity location such as Ga. vents actually cause more of an issue in a crawlspace. Encapsulation is used to reduce the relative humidity in the space. http://www.energyvanguard.com/crawl-space-encapsulation-features

If you are running dryer vents. heating,air or plumbing through this area there should be interior floor access. Traditionally this is built into a closet in the new structure.

Are there any particular codes in IRC that talk about having access to vents and plumbing? (I know it's common sense, but my contractor didn't think so...)

From SECTION R408 UNDER-FLOOR SPACE

R408.3 Unvented crawl space. Ventilation openings in under-floor spaces specified in Sections R408.1 and R408.2 shall not be required where:

1.
Exposed earth is covered with a continuous Class I vapor retarder.
Joints of the vapor retarder shall overlap by 6 inches (152 mm) and
shall be sealed or taped. The edges of the vapor retarder shall extend
at least 6 inches (152 mm) up the stem wall and shall be attached and
sealed to the stem wall; and2. One of the following is provided for the under-floor space:2.1.
Continuously operated mechanical exhaust ventilation at a rate equal to
1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7m2)
of crawlspace floor area, including an air pathway to the common area
(such as a duct or transfer grille), and perimeter walls insulated in
accordance with Section N1102.2.9;2.2. Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2)
of under-floor area, including a return air pathway to the common area
(such as a duct or transfer grille), and perimeter walls insulated in
accordance with Section N1102.2.9;2.3. Plenum in existing structures complying with Section M1601.5, if under-floor space is used as a plenum.

R408.4 Access.
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
by 610 mm). Openings through a perimeter wall shall be not less than 16
inches by 24 inches (407 mm by 610 mm). When any portion of the
through-wall access is below grade, an areaway not less than 16
inches by 24 inches (407 mm by 610 mm) 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 Section M1305.1.4 for access requirements where mechanical equipment is located under floors.

Is there anything in relation to an inaccessible space that isn't above earth? They (contractor and city and contractor's hired "expert") say that since it's above concrete (we think there's no exposed dirt...) that it's not covered under that code... But seems crazy to have water, a drain and ductwork where it can't be reached w/out tearing out the floor. But I can't find anything about an inaccessible space that is above cement...would be like a crawl space, but you can't crawl in there... You can look in the space from our basement, but there's maybe 2 inches between the floor and the floor joists...

R408.5 Removal of debris.

The under-floor grade shall be cleaned of all vegetation and organic material. All wood forms used for placing concrete shall be removed before a building is occupied or used for any purpose. All construction materials shall be removed before a building is occupied or used for any purpose.

Here is the link.

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_4_sec008.htm

Here is the entire 2012 IRC. There really are not many significant changes from year to year, so if you are going by another year's code, you can usually assume it is the same. (Checked, GA is 2012)

http://publicecodes.cyberregs.com/icod/irc/2012/index.htm

You may want to contact this person.

GA Dept of Community Affairs:

Office of Construction Codes

Ted Miltiades, Director

60 Executive Park South, N.E.

Atlanta, GA 30329-2231

Phone: (404) 679-3106

Ted.Miltiades@dca.ga.gov

More GA info

https://www.iccsafe.org/about-icc/government-relations/map/georgia/

thanks so much Fred S!