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Minimum skim coats



"Minimum skim coats," in the Floor Preparation forum, begins: "When working with hard surface flooring such as vinyl, vct or linoleum and skim coating the slab is necessary, what ..."

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Old September 22, 2013, 04:28 PM   #1
RFI
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Minimum skim coats


When working with hard surface flooring such as vinyl, vct or linoleum and skim coating the slab is necessary, what is your standard for number of skim coats with grey patch? For me the magic number seems to be three coats. This is a pretty consistent number for me.

Also when trying to encapsulate existing adhesive residue how many coats do you usually apply?

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Old September 22, 2013, 04:50 PM   #2
Steve Forbo
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It really depends on the job, and more importantly, the guy patching. If you are using junk patch like Mapei Plani or CMP Grey, it would take the best patcher 3 coats to get it smooth. If you are using Ardex FF and have a properly scraped and swept floor, then one coat, possibly 2 if it is bad.
If a floor is in real bad shape, I either self level or do a 50/50 coat of Ardex SDP/FF, then back trowel and hit it with a single finish coat of FF.
The CMP H2O is excellent for real bad subfloors.
Patching/skim coating is truly an art form, and you can either do it right, or you can't....it's that simple. I have seen many a floor get worse than they were due to people who don't know how to patch.
Also, Mixing the patch to the right consistency is extremely important. I see too many people mix patch way too thin and watery. It simply does not fill the voids, and also becomes very dusty when dry. For example, when mixing Ardex FF, it should be like peanut butter, and you should not be able to pour it out of the bucket, you need to scoop it out. I think this is where most people have the biggest problem. It is easy to paint a floor grey with floor patch, but it takes a true craftsman and the right product to fix the floor in one to two coats.
Most important to me is a properly scraped and swept floor prior to patching. Then knowing exactly when to back trowel/scrape your first coat. The final coat should NEVER need to be scraped or swept. It should be smooth as glass...
Steve

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Old September 22, 2013, 05:30 PM   #3
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TRICK QUESTION


There's really nothing STANDARD about how much prep is needed.

#1 hassle in the industry (resilient) is the confusion/deception/misinformation/DISinformation over this concept.

If it takes more than two coats it's certainly not a "skim coat" at all in my terminology.

Two coats is not really a skim either. Skim coat is a quick and light covering of the entire area with a thin layer of patch.

Two coats means to me there's "floating" involved. That means there are deeper fills or more severely unflat, irregular conditons that take TIME and SKILL to trowel out. The first coat should be done well enough so that the second coat is in fact little more than a light skim.

Three coats means HEAVY FLOOR PREP in my book.

No way in hell there's some standard measure of that.

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Old September 22, 2013, 06:08 PM   #4
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Inconsistant mixing is the #1 cause of problems in my experience.

Of course I am geared to looking at failed floors, rarely am I called to look at a "good" job.

Why can installers not read and follow directions? Where I live everybody mixes on the floor, this means that they did NOT measure anything.

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Old September 22, 2013, 06:21 PM   #5
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The correct answer is,as many as it takes until the floor is smooth.I use Ardex Feather finish and i can usually get the floor smooth in 1 coat,at most 2.Even the roughest floors can be smoothed in 2 coats if you work the patch right,use your trowel correctly and have tons of experience.I agree with forbo king about the most peeps do not mix the ardex right and have issues like taking 3-4 coats,not sticking.I also use a mixer and do not hand mix which makes a huge difference in the patch itself during mixing.But hey,that's just me.I patch all control joints at least twice,sometimes 3 if real wide and deep.

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Old September 22, 2013, 06:40 PM   #6
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So when skimming over adhesive residue do you consider one coat enough?

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Old September 22, 2013, 06:48 PM   #7
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Incognito said View Post
TRICK QUESTION


There's really nothing STANDARD about how much prep is needed.

#1 hassle in the industry (resilient) is the confusion/deception/misinformation/DISinformation over this concept.

If it takes more than two coats it's certainly not a "skim coat" at all in my terminology.

Two coats is not really a skim either. Skim coat is a quick and light covering of the entire area with a thin layer of patch.

Two coats means to me there's "floating" involved. That means there are deeper fills or more severely unflat, irregular conditons that take TIME and SKILL to trowel out. The first coat should be done well enough so that the second coat is in fact little more than a light skim.

Three coats means HEAVY FLOOR PREP in my book.

No way in hell there's some standard measure of that.

Trick question? Yes and No! I have been traveling a lot lately and have been seeing different opinions on floor prep and skimming floors. Some of it depends on area and the brand of patch available in that location.

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Old September 22, 2013, 07:10 PM   #8
Mike Antonetti
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I've eliminated a lot of skim coating and patching by diamond grinding flat whenever possible and always try to make it possible, why patch wait to dry, light scrape vacuum and patch again. Every situation is different but we've saved a lot of time. Say you have drywall /paint on slab, you have to clean this up anyway, my as well use the diamond grinder with bac, clean and flatten simultaneously , a scraper blade doesn't even get residue off completely. Just my theory of removing instead of adding , especially adhesive residue.

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Old September 22, 2013, 07:10 PM   #9
icanlayit2
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For cutback or any asphalt glue,2 coats at least.If you still have black bleed through 2 coats then a 3rd is needed.For most other adhesives i always try to remove as much as possible so yes,1 coat is often enough.I also use a buffer with either a pad or 1 with the bits in it.


Last edited by icanlayit2; September 22, 2013 at 07:12 PM. Reason: *forgot the buffer
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Old September 22, 2013, 08:18 PM   #10
Steve Forbo
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Mike Antonetti said View Post
I've eliminated a lot of skim coating and patching by diamond grinding flat whenever possible and always try to make it possible, why patch wait to dry, light scrape vacuum and patch again. Every situation is different but we've saved a lot of time. Say you have drywall /paint on slab, you have to clean this up anyway, my as well use the diamond grinder with bac, clean and flatten simultaneously , a scraper blade doesn't even get residue off completely. Just my theory of removing instead of adding , especially adhesive residue.

The ONLY way to get it right...
But in this case, the old terrazzo was so bad, it had to be skim coated and touched up in a few spots.....
Attached Thumbnails (click to enlarge)
grind.jpg   grind-2.jpg  

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Old September 22, 2013, 09:20 PM   #11
Mike Antonetti
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Nice machine, way outa my league and can get a lot flatter than what I have. Can I borrow it?
Skim coats do dry quick, divots add to coats.

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Old September 23, 2013, 05:17 AM   #12
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That subject is too deep for a quick answer. My soapbox starts with "When I started working (40 yr. ago) concrete finishers could make a flat slab" First off I don't like to skim over existing adh. I know it is approved practice but I find that slabs need to be ground to bare conc. I use " Dependable" skimcrete with primer.

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Old September 23, 2013, 03:48 PM   #13
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Anyone got or tried one of these to check flatness of floor?

GSL 2 Surface Laser | Bosch
Attached Thumbnails (click to enlarge)
bosch-gsl2-surface-laser.png  

Last edited by Jim McClain; September 23, 2013 at 04:29 PM. Reason: uploaded picture
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Old September 23, 2013, 04:30 PM   #14
Mike Antonetti
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I've got a rotary laser level, different brand though. I want an electric plug in for a bright, long duration 5-8 hours on with no loss of brightness.
I think we 're talking three different things now.
1. Smooth slab
2. Flat slab
3 level slab
Ok I'll give up all my wishes for everyone to have these. Priceless

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Old September 23, 2013, 06:01 PM   #15
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RFI said View Post
Trick question? Yes and No! I have been traveling a lot lately and have been seeing different opinions on floor prep and skimming floors. Some of it depends on area and the brand of patch available in that location.
****************************
If you NEED three coats of Ardex FF on a regular basis I'm suspecting a watered down mixture.

OK, that's an opinion.

But the final product is either up to scratch or over time the patch gives way--------not enough integrity to hold up to heavy traffic or not enough integrity to withstand the tensile pressures of the adhesive and materials expanding and contracting from normal temperature change. Shrinking, bubbles, curling.........whatnot.

That's the reason you don't water it down, right?

As far as those substandard brands-------ALL of them in my opinion besides Ardex------ God bless you if you can turn over high quality resilient work using that kind of patch. I'm still on occasion sent out with those bags. I'm OK with it until the shop/boss/dispatcher fails to figure in 2-300% extra LABOR dicking around with patch that's THAT much harder to work with.

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