Access

[Energystar]

R807 Attic access has previously been discussed on this site. This code section defines a minimum sized space that must be provided with access. I believe the size of this space has not kept up with our required insulation depth but at least there is a minimum.



When it comes to under-floor spaces, the rules are somehow different. There is no space too small to exclude it from accessibility. “Access shall be provided to all under-floor spaces.”



What if the space between the bottom of the joists and the surface below is only 6” or less? Does one need to provide access to the entire area?

Case in point: A 200 s.f., class V sunroom addition will be constructed over an existing patio. A trench footing will be installed around the perimeter of the patio that will extend 8” above the ground and 4 to 6” above the patio. A vapor barrier will be installed over the patio and the perimeter will be insulated with spray foam. The floor will be oak flooring and the underfloor space will communicate with the existing, finished basement. Code requires that an access opening at least 18”x24” must be provided in the floor since there is no room in the surrounding walls.

My question is, to what end?

 

[Yankee Chronicler]

From the 2021 IRC Commentary:

 

[Paul Sweet]

Ask for a code modification based on (1) not piping or mechanical equipment under the floor and (2) insufficient space for a person to enter.

 

[Sifu]

I think the code sections you reference are only for the openings, not the actual crawlspace. Min. clearances are somewhat specified by IRC 317. I say somewhat because they can be usurped by treated lumber, but in a typical floor frame I think that is rare. In what you describe I don't even think treated lumber would be required with the vapor barrier (I don't treat a slab on bare earth any different than I treat bare earth). The few times I have seen what you describe have been garage finishes with raised floor systems, or similar porch/slab frame-overs. Definitely not optimal, but min. code seldom is.

I would require the access opening, and let them lament their design later (I think that would be the "end" of which you inquire). Hope they NEVER need to fix anything under the floor.

 

[Mr. Inspector]

Would a space under an addition that is on piers be defined as a crawlspace and need the minimum access opening? The floor is just 12" above the ground and it is open between the piers so the required 16 x 24 access opening won't work.

IRC Definition of crawlspace: An underfloor space that is not a basement.