Floor Flatness and Levelness and Deflection

[Luigitree]

This question is a two part-er:
1.) In our concrete specifications we indicated required F(F) and F(L) numbers for floor flatness and levelness. The main reason these are spec'd is for requirements of the flooring. Per ACI 117, these measurements are to be taken at a maximum of 72 hours after the concrete has been poured (ie, prior to shoring being removed). I understand that this is a measure of the quality of the finish, but won't deflection play a large role in this number? Doesn't the service life deflection have a lot to do with the application of the flooring?

2.) Flooring specs often refer to the old "x" of deflection over 10' " as opposed to F(F) and F(L) numbers. Is this just a disconnect in the industry?

Overall, I'm just not sure what people are seeing, and what problems/solutions have come up. Thanks in advance!

 

[RHTPE]

FF & FL numbers are a specification and how well they are achieved is a measure of the contractor's ability to perform.

Actual structure deflection (of elevated slabs) reflects back on the designer's ability to anticipate the structure's performance and provide a proper design.

Structure deflection may have an impact on the flooring, but it will depend upon what the specific flooring is.


Ralph
Structures Consulting
Northeast USA

 

[Luigitree]

Thanks. I guess specifically I am asking that if when a flooring manufacturer gives a floor flatness requirement are they actually referring to the shored flatness, or are they referring to deflection as well? My sense from searching around is that they don't actually know what they mean...

 

[KootK]

I would think that, even inadvertently, they would have to mean flatness with the effects of deflection included. At the end of the day, I believe that it is curvature, of any sort, that affects their products' performance.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[thaidavid40]

In these parts we normally don't specify an F_f value for elevated or suspended floor slabs, just the F_l value, because of the deflection complications. We do specify that the contractor is responsible for any concrete overruns necessary for a level slab (accounting for deflection).
Dave

Thaidavid

 

[RHTPE]

thaidavid40 - I agree that the contractor should be responsible for concrete overruns needed because of formwork/shoring deflections. However, If the FL numbers are found to be satisfactory prior to the removal of formwork/shoring, any subsequent leveling mixes required because of the structural deflection should not be the contractor's responsibility.



Ralph
Structures Consulting
Northeast USA

 

[Ron]

The manufacturers are concerned about the floor surface at the time of placement of their product, not the construction specification. Their product may be installed at any time during the life of the floor structure, not just at construction, and they expect their specification to be met (usually 1/8" in 10' or 1/4" in 10') even if it requires a leveling course of some type.

Ff and Fl are generally not related to load induced deflection as they are to be measured while the floor is fully supported and not loaded.