Residential Slab Flatness

[boo1]

What is the U.S. code requirement for slab flatness in in home construction and the code reference?

 

[Focht3]

I don't think there is one...

 

[sc]

In Australia the tolerance is generally +- 5mm, but most contracters are much better and can generally acheive +-2mm judging by the ponding.

regards
sc

 

[NickDemos]

The slab in my basement is very flat. After a few water spills, I would have rather pitched it to the trench drain around the perimeter of the slab, maybe 0.5%. Flat may not be the most desireable.

 

[SoilRocks]

This is not really my forte - but, there are very specific methods for measuring slab flatness (ASTM I believe). This will spell out the method for measuring the flatness. However, the requirements are not set in stone anywhere that I know of. It depends on local requirements, project requirements/specifications and local standard of practice. Usually you are talking about interior living spaces. Garages, and sometimes basements (as NickDemos mentioned), are sloped to drain, and are not subject to these requirements.

 

[BigH]

Our bridge decks on my current job are +10mm/-5mm. On the Vancouver Skytrain at-grade section it was +5mm/0mm. These are industrial/heavy civil projects - still, I would say that the flatness (or the deviation from the desired % slope for any drainage (assuming basement floor or garage floor) shouldn't be more than a couple of mm in a 3m length on the straight edge.

 

[Ron]

Flatness can be whatever is desired by the specifications. For residential, there is usually not a specified flatness, though a "rule of thumb" commonly used but rarely checked and enforced was 1/4" in 10 feet. This is not truly a flatness profile specification in today's vernacular.

Floor flatness is generally specified now by Ff (flatness) and FL (levelness) profiling criteria. ACI accepts this protocol and there are accepted standards for the testing. As an example, a specifier might state a flatness requirement of Ff=25 and levelness of FL=15. Some would consider this to be close to the 1/4" in 10 feet requirement, but there is no true correlation.

Keep in mind (noting NickDemos's statement) that flatness and levelness are different. A sloped floor can have a flat profile. Flatness refers to the floor surface profile, not the state of the levelness of the floor.

 

[boo1]

Research found:
"The F-Number System is the new American Concrete Institute (# 117) and Canadian Standards Association (# A23.1) standard for the specification and measurement of concrete floor flatness and levelness. F-Numbers replace the familiar "1/8th inch in ten feet" type specs that had proven unreliable, unmeasureable and unrealistic.

The new standards include two F-Numbers:

FF for flatness and FL for levelness

Flatness relates to the bumpiness of the floor, while levelness describes the tilt or pitch of the slab. The higher the F-Number, the better that characteristic of the floor. "

from:

http://faceco.com/40q.html