| Author |
Message |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 289
Registered: 08-2004
| | Posted on Monday, January 11, 2010 - 11:03 am: |    |
I have a 2 part question. One, how exactly does one field measure concrete slabs to see if they comply with ACI's Ff and Fl values?
Two, my spec calls for F(f)25 and F(l)20. A VCT manufacturer is stating that the edges of the concrete slab curl excessively at the saw cut joints (their literature calls for 1/8 inch in 19 feet for levelness). How does one reconcile the ACI F(l) values with the 1/8 inch in 10 feet measurement? And, then, assuming it curls a tiny bit to much, who's responsibility would it be to either grind or install a level compound? My spec (based on Masterspec) includes the following:"Use trowelable leveling and patching compound to fill cracks, holes, and depressions in substrates", but doesn't specifically address curling. Any thoughts are appreciated! |
Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP
Senior Member
Username: specman
Post Number: 826
Registered: 03-2003
| | Posted on Monday, January 11, 2010 - 11:18 am: | |
An article (actually, an online course) that I've used is "Concrete Slab Finishes and the Use of F-Number System" at http://www.pdhonline.org/courses/s130/s130.htm.
However, I've received feedback from flooring installers that they actually prefer that areas indicated to receive a resilient flooring NOT be sawcut--just leave it to crack where it wants. They state that it is easier to handle the cracking than the sawcut joints with floor leveling compound for the reason you're experiencing.
Ron Geren, AIA, CSI, CCS, CCCA, SCIP
www.specsandcodes.com |
Nathan Woods, CCCA, LEED AP
Senior Member
Username: nwoods
Post Number: 326
Registered: 08-2005
| | Posted on Monday, January 11, 2010 - 11:39 am: | |
Do you have access to ACI 302.2R-06? This goes into some detail about curling and moisture sensitive flooring. To sum it up, make sure you have adequate rebar in the slab and curling is less of an issue.
To measure FF and FL numbers, I belive it requires a special machine, sold or licensed by the author of that measuring standard. I have seen them use a "Dipstick 2272 Floor Profiler" machine, that looks a bit like a laptop bolted to hand held metal detector.
As for your "1/8" in 19'-0", that is exceptionally flat. Actually qualifing as SuperFlat, which is a very expensive level of concrete finish to perform or provide. According to Section 4.5.6 of ACI 117-90 (there are newer versions available now), “Specifications for Tolerances for Concrete Construction and Materials,” suggests that 1/8" in 10' equates to FF=50. For comparison, our standard office slab is specified as FF=30/FL=25. |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 291
Registered: 08-2004
| | Posted on Monday, January 11, 2010 - 11:49 am: | |
Nathan: that was a typo - should have been 1/8 inch in 10 feet. |
Marc C Chavez
Senior Member
Username: mchavez
Post Number: 372
Registered: 07-2002
| | Posted on Monday, January 11, 2010 - 11:50 am: | |
To answer your question
Answer 1. I love this one and have many fights over it.
Ff and Fl are measured with little machines see ASTM E 1155 for the machine and ACI 117 and ACI 302.1R Chapter 8 (8.15) talk about it.
The REALLY short version is that if you have asked for these numbers they have to give them to you – AT THE TIME of finishing unless you say differently. This standard 302.1R ONLY applies to slabs on grade and suspended slab – while shored. The minute the supports are gone – it does not apply.
Unless you have asked for this flatness for the floor at the time of FINAL finish flooring application. – they will fight this too. the ASTM does NOT limit the use of the technique to wet concrete finishing. it is just a technique for measuring floor flatness.
And yes it is hard to get 1/8 in 10 (or worse yet 1/8 in 19) without:
1. the slab being on grade
Or
2. a complete cover of the floor by self leveling compound
And remember 1/8 in 10 is the same as one 1/8 inch rise over a 10 foot length (think a hill) is the same at (5) 1/8 inch rises(es) in the same length (think saw tooth) both of these are 1/8 in 10 feet.
Answer 2. If the floor is WAY out of flat the floor person will say that this is NOT a small patch or hole filling which is usually covered in the flooring spec. If the floor has curled (also talked about in the ACIs I mention above) then the G.C needs to fix it.
Thus the never-ending fight between the flooring warranty and the hurry up – “damn the torpedoes” attitude of General Contractors.
To answer #2 what does your concrete spec say about flatness, curing, does it reference ACI 117 and 302.1R? if so how, does it reference the Ff Fl numbers or does the flooring spec reference them?
Read the ACI docs and call me in the morning.
PS both of these docs are located in a handy little volume entitled the “Field Reference Manual specifications for Structural Concrete ACI 301-05 with selected Aci references. Publication SP-15 (there may be a later then 05 version out)
and that is the short version! |
Mark Gilligan SE, CSI
Senior Member
Username: mark_gilligan
Post Number: 252
Registered: 10-2007
| | Posted on Monday, January 11, 2010 - 01:58 pm: | |
The above advise is good.
Unless you have some special needs for flatness, such as a warehouse structure with fork lift trucks, or you have a lot of slab I would be comfortable with the 10 foot ruler. Sure there is more ambiguity than with the flatness numbers but you will still address the real problems. Go back to an existing concrete slab that everybody is happy with and check the flatness using either system. My guess is that you will not sweat it too much in the future.
1/4" in 10' has been used a lot and is more likely what you will get. I do not like to specify tighter criteria than I need or that I am willing to hold the contractor's feet to the fire on.
I agree with Ronald, put in reinforcing and omit the crack joints. In my experience most slabs with saw cut joints will have cracks that are not at the joints. |
David Stutzman
Senior Member
Username: david_stutzman
Post Number: 60
Registered: 07-2002
| | Posted on Monday, January 11, 2010 - 08:20 pm: | |
Robin, I suggest you check http://www.allenface.com/ for information on Ff and Fl, how the values are measured and the equipment required. The values are a statistical analysis of the root mean square for the surfact profile.
Allen Face developed the method and offers a sample spec on his website. If you have a chance to hear Allen speak he give very interesting presentations on the subject. |
Phil Kabza
Senior Member
Username: phil_kabza
Post Number: 417
Registered: 12-2002
| | Posted on Tuesday, January 12, 2010 - 10:39 pm: | |
I agree with Mark's comments above and his endorsement of Ron's comments. The Ff / Fl system works well for overall flatness control necessary for getting fixtures aligned or controlling high lift vehicles, but the straightedge measure works better for local control. If you want the slab to be flat, use the former; if you want the slab to look flat, use the latter. And 1/8 inch in 10 foot is not realistic, which is apparent when you go watch concrete slabs being poured. We found that requiring use of a highway screed helped finishers achieve better flatness results. |
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