ACI 117-9, Level Alignment
ACI 117-9, Level Alignment
(OP)
In section 4.3.1.1, for tops of slabs-on-grade a number of 3/4" is given.
I read this to say that for a slab-on-grade, if the plans say to place this at 100'-0" elevation above sea level, and you also cite ACI 117 tolerances, you could be at 99'-1/4" or up to 100'-3/4", and the slab level alignment would still be OK.
Not a specific problem, but something I have to deal with.
If you interpret this section to meet something different please explain, maybe could it also be suggesting 3/4" out of level within the slab surface, ie, relative to the slab surface you can be 3/4" out of level? But over what distance? I think that is a separate issue that is dealt with in floor finish tolerances with the flatness scale (4.5.6).
Thanks in advance.
I read this to say that for a slab-on-grade, if the plans say to place this at 100'-0" elevation above sea level, and you also cite ACI 117 tolerances, you could be at 99'-1/4" or up to 100'-3/4", and the slab level alignment would still be OK.
Not a specific problem, but something I have to deal with.
If you interpret this section to meet something different please explain, maybe could it also be suggesting 3/4" out of level within the slab surface, ie, relative to the slab surface you can be 3/4" out of level? But over what distance? I think that is a separate issue that is dealt with in floor finish tolerances with the flatness scale (4.5.6).
Thanks in advance.






RE: ACI 117-9, Level Alignment
Flatness is a different animal
RE: ACI 117-9, Level Alignment
RE: ACI 117-9, Level Alignment
Ron- I think this is up your alley and was hoping you'd chime in.
Lets just say that I am being forced to use this section for residential slabs-on-grade and leave it at that.
To me this means that anywhere on the slab that you measure, it must be within that 3/4" limit. Regardless of the set elevation requirement (say there is no actual number, like 100'-0" above sea level), essentially this interpretation would restrict you to 1-1/2" of elevation variation between any two points on a slab regardless of the distance between the two points.
Part two of this issue I am dealing with addresses local variations in the floor slope or flatness, versus global differences which are given above by "levelness".
I think I got it....
RE: ACI 117-9, Level Alignment
RE: ACI 117-9, Level Alignment
In the "level" section, there is no mention of horizontal distance criteria. This is why I originally assumed the numbers apply to tolerance within a stated elevation on the plan, such as Finished Floor El = 100'-0".
The flatness is addressed in another section. And agree fully there, it is absolutely a function of horizontal distance.
RE: ACI 117-9, Level Alignment
The annoying bit is the measurements normally have to be taken within a few days of casting the slab.