| Author |
Message |
Dewayne Dean
Senior Member
Username: ddean
Post Number: 102
Registered: 02-2016
| | Posted on Monday, November 21, 2016 - 11:39 am: |    |
Greetings fellow specifiers. Are statements 2. and 3. below compatible with each other?
If you have 2. do you need 3.?
2.Finish surfaces to the following tolerances, measured within 24 hours according to ASTM
E 1155/E 1155M for a randomly trafficked floor surface.
a. Specified overall values of flatness, F(F) 35; and levelness, F(L) 25; with minimum
local values of flatness, F(F) 24; and levelness, F(L) 17; for slab-on-grade.
3. Finish and measure surface so gap at any point between concrete surface and an unleveled
freestanding 10-foot (3.05 m) long straightedge, resting on two high spots and placed
anywhere on the surface, does not exceed the following:
a. 1/8 inch (3.2 mm). |
William C. Pegues, FCSI, CCS
Senior Member
Username: wpegues
Post Number: 950
Registered: 10-2002
| | Posted on Monday, November 21, 2016 - 11:59 am: | |
These are 2 different methods to determine flatness/levelness of slabs. You should use one or the other and ACI recommends that you use of the FF/FL system in 2.
ACI publishes a annotated version of ACI-117 that explains the systems and provides equivalents between them. And, you should also reference ACI 117 in addition to ASTM E1155. You should not reference the E1155M version unless you want to give the contractor the option of using whatever he wants of either US or Metric, usually you want to confine them to one or the other.
William C. Pegues, FCSI, CCS, SCIP Affiliate
WDG Architecture, Washington, DC | Dallas, TX |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 794
Registered: 01-2008
| | Posted on Monday, November 21, 2016 - 12:01 pm: | |
Dewayne
My recommendation is use 2.
#3 is from a bygone era. |
Dave Metzger
Senior Member
Username: davemetzger
Post Number: 665
Registered: 07-2001
| | Posted on Monday, November 21, 2016 - 12:01 pm: | |
Specify just f number tolerances or straightedge tolerance, not both. BTW, straightedge tolerance measures flatness only, not levelness. |
J. Peter Jordan
Senior Member
Username: jpjordan
Post Number: 921
Registered: 05-2004
| | Posted on Monday, November 21, 2016 - 12:27 pm: | |
Although most would agree with Mr. Yancey's comment, I think it is more complicated that that. The ASTM E 1155 testing is a statistical measure meaning that one could have local variances that would not be in compliance with the 10-ft straight-edge measurement. Compliance with flatness restrictions is important for large-format tile installations.
J. Peter Jordan, FCSI, AIA, CCS, LEED AP, SCIP
|
Guest (Unregistered Guest)
Unregistered guest
| | Posted on Monday, November 21, 2016 - 12:26 pm: | |
Use #2 for making sure the concrete is placed properly.
Then after the slab cures and you're trying to see if you need to do any additional work to prep for flooring finishes you might end up measuring using #3.
For example, TCNA has an older article that discusses why you would want to use a straightedge method in addition to F(F) numbers.
https://www.tcnatile.com/images/pdfs/2013%20TCNA%20Handbook%20Addresses%20Concrete%20Slabs.pdf |
Ronald J. Ray, RA, CCS, CCCA, CSI, AIA
Senior Member
Username: rjray
Post Number: 147
Registered: 04-2004
| | Posted on Monday, November 21, 2016 - 01:08 pm: | |
ASTM E1155 does not include the 24 hour time period you referenced. ASTM E1155 does include a note stating the ACI 117 requirement that floor flatness and floor levelness be tested within 72 hours after completion of the installation of the concrete floor.
Some believe that ASTM E2255 is limited to testing cast-in-place concrete slabs-on-grade. However, ASTM E1155 includes no limitations, nor does ACI 117. ACI 117 does state the for elevated slabs, testing should occur prior to removing shores.
The local values you list do not correspond to ACI 117 recommendations, which are minimum local values should be 3/5 of overall values.
ACI 117 still includes the 10-foot straight edge testing. ACI 117 list 1/4 inch as the minimum value for 90 percent compliance, not 1/8 inch as you list in your post.
You may want to verify with manufacturers of finish floor coverings if they require the 10-foot straight edge method. My memory is that fro some floor finishes, the 10-foot straight edge test is preferred, but I can’t recall which finishes.
If your project will involve defined traffic wheel paths, you may want to consider using ASTM E1486 test method. |
John Gallup (Unregistered Guest)
Unregistered guest
| | Posted on Monday, November 21, 2016 - 05:23 pm: | |
Good Afternoon. While a floor's Ff value reflects the aggregate of many measurements and is an indication of the overall flatness of the concrete, as Ff numbers are derived from many measurements, concrete which meets a specified Ff of 35 will typically maintain areas which do not meet the required flatness tolerances to receive (ceramic or stone) tile. The Tile Council of North America requires substrate flatness tolerances for "large Format" tile (tiles which maintain any edge 15" in length or greater), to be no more than 1/8" in 10.0' ft. from the required plane, with no more than a 1/16" in 24", when measured from the high points of the surface.
In addition to the lack of correlation between the ASTM E-1155 method for determining floor flatness, and a traditional straight edge method, is the fact that ASTM E-1155 requires that measurements be taken within 72 hours of concrete placement, long before concrete curling and shrinkage has culminated. As a result, flatness conditions can change signifigantly after completion of an Ff E-1155 test. It is for this reason that the Tile Council of North America (TCNA) continues to reference a traditional 10' straight edge method in their handbook.
Perhaps the best approach is to provide a bid allowance for any floor prep required in order to bring the floor into tolerance. The most efficient means of providing the required floor flatness for large format tile installation is the inclusion of a hydraulic cementitious self-leveling underlayment, as per TCNA method F-205. Please read the section in the TCNA Handbook regarding the disparity between Ff flatness tolerances and the 10' straight edge method. In addition, I have written more on this subject on the following link:
https://www.linkedin.com/pulse/concrete-flatness-values-f-numbers-vs-straight-edge-method-gallup |
Dewayne Dean
Senior Member
Username: ddean
Post Number: 103
Registered: 02-2016
| | Posted on Tuesday, November 22, 2016 - 10:05 am: | |
Gentlemen,
Thank you for the insights and information. |
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