Code Reference - Grade Outside the Building

[CPENG78]

Need help. I'm looking for the building code reference, either CBC, IBC or both from what I recall the requirement for grade outside the building to be a certain height from finish floor. I recall its 6 inches if the finish grade outside is concrete and 8 inches if its dirt. Can someone point me to the code reference?

 

[Ron]

Are you looking for the distance to grade or the slope from the building?

The distance to grade from exterior finish depends on the finish and the substrate. The slope away from the building is required to be at least 5 percent under the IBC.

 

[bimr]

R408.6 Finished grade.
The finished grade of under-floor surface may be located at the bottom of the footings; however, where there is evidence that the groundwater table can rise to within 6 inches (152 mm) of the finished floor at the building perimeter or where there is evidence that the surface water does not readily drain from the building site, the grade in the under-floor space shall be as high as the outside finished grade, unless an approved drainage system is provided.

http://www2.iccsafe.org/states/newjersey/nj_residential/pdfs/nj_res_chapter4.pdf

Generally, it is the siding that should be above the grade, not the finished floor.

R404.1.6 Height above finished grade. (2009)
Concrete and masonry foundation walls shall extend above the finished grade adjacent to the foundation at all points a minimum of 4 inches (102 mm) where masonry veneer is used and a minimum of 6 inches (152 mm) elsewhere.

The second consideration is that the overflow level of building fixtures should be above the level of the sewer manhole in the street unless an overhead sewer is used.

It is good practice to have the building floor level above the level of the street,

 

[CPENG78]

I've definetely come across the grading away from building face, I believe chapter 18 of the IBC.

What I'm looking for is the height from finish floor to adjacent grade outside the building. I have across some references in the IRC (as bimr points out) but nothing in the CBC or IMC. I was under the impression it had been adopted there as well. Again, from past experience in CA, it was a minimum of 8 inches if it was dirt or 6 inches if it was concrete/hardscape. So its the reference in the CBC or IBC that I'm interested on.

 

[bimr]

Don't believe there is any such thing. On a city street, the finish floor is the same elevation as the finished grade.

What you are saying is there has to be a step up into a building.

 

[CPENG78]

BIMR - That is correct, there would represent a step to finish grade outside. However I've come across ways around this.

All,
I actually found the reference in the code that I was looking for and thought I would share:

2012 IBC 2304.11.2.2 - "Wood supported by exterior foundation walls. Wood framing members, including wood sheathing, that rest on exterior foundation walls and are less than 8 inches (203 mm) from exposed earth shall be of naturally durable or preservative-treated wood"

2013 CBC 2304.11.22 - "Wood supported by exterior foundation walls. Wood framing members, including wood sheathing, that rest on exterior foundation walls and are less than 8 inches (203 mm) from exposed earth shall be of naturally durable or preservative-treated wood" - California however does have the exception for DSA-SS and OSHPD 1, 2 &4, "At exterior walls where the earth is paved with an asphalt or concrete slab at least 18 inches (457 mmm) wide and draining away from the building, the bottom of the sills are permitted to be 6 inches (152 mmm) above the top of such slab. Other equivalent means of termite and decay protection may be accepted by the enforcement agency"

Depending on the project, where I've come across it is via the height separation of 6 or 8 inches. I've also seen where a stem wall is introduced as part of the foundation to raise the sill plate elevation. In situations where you are flushed with outside grade, that is where alternates as pressure treated wood, or even non-wood construction are considered. I've attached a sketch from one of my recent projects. In this case, the red annotations were only trying to convey the height differential to another team member if we had wood construction. The project itself was not using wood for this installation.