slc over lightweight concrete....no bueno or what? - Contractor Talk - Professional Construction and Remodeling Forum

wopachop · 01-23-2009, 12:50 AM

girl has a second story apt and wants tile on bath floor. right now its vinyl flooring over lightweight concrete.

what are my options to level..? the self leveling cement bag says "not recommended for use on lightweight concrete."

thanks fellas...peace

PrecisionFloors · 01-23-2009, 08:04 PM

Not saying it is recommended or approved by ANYONE but... I have had success in that very same scenario by priming floor with a latex floor primer, skim coating with Ardex Feather Finish and then K-15 SLC. I've done two small 6x5 baths that and it stuck like a mofo and was dead flat. These were worth the risk to me though as it was only 60sf of tile....I would have thought differently if it was hundreds of feet.

wopachop · 01-24-2009, 12:10 AM

rock on thanks brotha!!

i found this while learning what feather finish was. lightweight concrete is similar to gypsum is some ways....what are your guys thoughts about priming like what is copy/pasted below?

how does their primer differ from a regular latex floor primer?
------------------------------------------------------------
If the substrate is a gypsum underlayment that will not be removed, double priming of the gypsum is necessary to consolidate what may be a dusty surface prior to installing ARDEX FEATHER FINISH. Make an initial application of ARDEX
P 51™ PRIMER mixed with 3 parts water using a soft push broom. Do not leave any bare spots. Remove all puddles and excess primer. Allow thorough drying such that the film of primer does not re-emulsify in water (approximately 1 to 3 hours) before proceeding with the second application of
ARDEX P 51 diluted 1:1 with water. Allow thorough drying
to a clear, thin film (min. 3 hours, max. 24 hours).
-------------------------------------------------------

PrecisionFloors · 01-24-2009, 12:26 AM

Quote:

Originally Posted by wopachop

rock on thanks brotha!!

i found this while learning what feather finish was. lightweight concrete is similar to gypsum is some ways....what are your guys thoughts about priming like what is copy/pasted below?

how does their primer differ from a regular latex floor primer?
------------------------------------------------------------
If the substrate is a gypsum underlayment that will not be removed, double priming of the gypsum is necessary to consolidate what may be a dusty surface prior to installing ARDEX FEATHER FINISH. Make an initial application of ARDEX
P 51™ PRIMER mixed with 3 parts water using a soft push broom. Do not leave any bare spots. Remove all puddles and excess primer. Allow thorough drying such that the film of primer does not re-emulsify in water (approximately 1 to 3 hours) before proceeding with the second application of
ARDEX P 51 diluted 1:1 with water. Allow thorough drying
to a clear, thin film (min. 3 hours, max. 24 hours).
-------------------------------------------------------

P 51 Is a latex floor primer....I shoulda just told ya to use their primer but, in all reality any would do the trick

wopachop · 01-24-2009, 11:58 AM

thanks cpt chaos!! two more questions if anyone has advice

1.do you always need to use some type of expansion joint foam along the walls? this particular bath is only 5x7...cant say for sure but lets pretend at its thickest the SLC is only 1/4" thick

2.what size and type of trowel or float do you want to apply feather finish with and how thick does a skim coat need to be to have strength and stick together?

mucho grassy azz

Dave Gobis · 01-24-2009, 07:20 PM

Your right, it is not approved by anyone. As long as the floor never gets wet, it would work. But long term, not a real good chance it will stay that way. I will cut and paste a piece in here from a technical document. Granted, it is a small bath, but this is the big picture.

Poured Gypsum underlayments can provide a satisfactory surface to receive and ceramic tile installation system. In general, ceramic tile can not be directly bonded to gypsum underlayments without use of a membrane system. The Tile Council of North America and all major manufacturers of lightweight underlayments recommend the use of a membrane system when installing ceramic tile. The few exceptions to this recommendation are proprietary in nature and suitability rests solely with the manufacturer. There are 4 industry approved methods for this product category.

F-200 Poured Gypsum Over Concrete (bonded)
F-180 Poured Gypsum Over Wood (not bonded)
RH-111 Poured Gypsum Over Concrete with Hydronic Heat
RH-122 Poured Gypsum Over Wood with Hydronic Heat.

Specific recommendations apply to each method listed in the TCA Handbook and should be reviewed prior to installation. Anticipated service levels should be met when tested under ASTM C627, the Robinson Floor Tester. Lightweight gypsum products used in these methods do share some basic recommendations. All lightweight product applicators must be approved by the manufacturer. As a licensed applicator they must provide an approved product installation per manufacturer’s instructions. All products should have a minimum of 2000# compressive strength when tested using ASTM C472, results of these tests should be available on request per manufacturer’s instructions. Floors should be dry prior to application of a membrane and not exceed 5# of moisture vapor emission (MVR) for fully adhered products and 10# of MVR for uncoupling membranes. When using humidity probes the product should be in the 75-80% range using a Delmhorst meter. All products require a surface primer prior to application and an overspray (or sealer) post application. Average drying times prior to application of primer and floor covering products can be from 5-7 days for a ¾” topping to 2 weeks or more for a 2” topping. Methods listed in the TCA handbook apply to ceramic tile products. Marble Institute of America recommends stone flooring products have a depth of 2” above the heat tubes in radiant applications to aid in heat dissipation and avoid thermal stripping induced stress.

PrecisionFloors · 01-24-2009, 08:00 PM

Quote:

Originally Posted by Dave Gobis

Your right, it is not approved by anyone. As long as the floor never gets wet, it would work. But long term, not a real good chance it will stay that way. I will cut and paste a piece in here from a technical document. Granted, it is a small bath, but this is the big picture.

Poured Gypsum underlayments can provide a satisfactory surface to receive and ceramic tile installation system. In general, ceramic tile can not be directly bonded to gypsum underlayments without use of a membrane system. The Tile Council of North America and all major manufacturers of lightweight underlayments recommend the use of a membrane system when installing ceramic tile. The few exceptions to this recommendation are proprietary in nature and suitability rests solely with the manufacturer. There are 4 industry approved methods for this product category.

F-200 Poured Gypsum Over Concrete (bonded)
F-180 Poured Gypsum Over Wood (not bonded)
RH-111 Poured Gypsum Over Concrete with Hydronic Heat
RH-122 Poured Gypsum Over Wood with Hydronic Heat.

Specific recommendations apply to each method listed in the TCA Handbook and should be reviewed prior to installation. Anticipated service levels should be met when tested under ASTM C627, the Robinson Floor Tester. Lightweight gypsum products used in these methods do share some basic recommendations. All lightweight product applicators must be approved by the manufacturer. As a licensed applicator they must provide an approved product installation per manufacturer’s instructions. All products should have a minimum of 2000# compressive strength when tested using ASTM C472, results of these tests should be available on request per manufacturer’s instructions. Floors should be dry prior to application of a membrane and not exceed 5# of moisture vapor emission (MVR) for fully adhered products and 10# of MVR for uncoupling membranes. When using humidity probes the product should be in the 75-80% range using a Delmhorst meter. All products require a surface primer prior to application and an overspray (or sealer) post application. Average drying times prior to application of primer and floor covering products can be from 5-7 days for a ¾” topping to 2 weeks or more for a 2” topping. Methods listed in the TCA handbook apply to ceramic tile products. Marble Institute of America recommends stone flooring products have a depth of 2” above the heat tubes in radiant applications to aid in heat dissipation and avoid thermal stripping induced stress.

Thanks for the info Dave. So you would you need a membrane prior to SLC, correct? I was hesitant to give this advice in the first place, as I knew it wasn't an approved method, however it did work pretty well (although I suppose as you mentioned water penetration through the grout may cause problems).

Quote:

Originally Posted by PrecisionFloors

Not saying it is recommended or approved by ANYONE but... I have had success in that very same scenario by priming floor with a latex floor primer, skim coating with Ardex Feather Finish and then K-15 SLC. I've done two small 6x5 baths that and it stuck like a mofo and was dead flat. These were worth the risk to me though as it was only 60sf of tile....I would have thought differently if it was hundreds of feet.

wopachop · 01-24-2009, 11:07 PM

so latex primer....feather finish...membrane....slc

what type of membrane like a sheet membrane or liquid roll on?

wopachop · 01-27-2009, 03:28 PM

me-brain dont know what type of membrane

Bud Cline · 01-31-2009, 12:02 PM

Noble CIS is one.

Shaughnn · 02-21-2009, 10:13 AM

Wopachop,
Noble's CIS applied with their EXT urethane adhesive is one method. I also use Schluter's DITRA membrane applied with Laticrete's 254 gray thinset (gray makes it easier to confirm coverage and contact without peeling the membrane back). For installation over gypcrete which are around plumbing fixtures or appliances, I also take the precaution of wrapping a waterproofing membrane *up* the walls by a couple of inches and waterproof the flooring membrane seams too. This extra step provides an additional assurance that an accidental leak or overflowing toilet isn't going to saturate the gypcrete, and cause a flooring failure.
For what it's worth, I believe that SLC is *never* a good idea over gypcrete. SLC's are saturated with water and all of that moisture is going to seep into the gypcrete, regardless of the primer you use. You might be better off using a combination of feather-finish and medium-set mortar?
Best of luck,
Shaughnn

Floordude · 02-24-2009, 10:12 PM

Never use a portland over a gypsum. It will blow off the gypsum. And I mean blow, too. Pop is not the word. Blowing up off the floor!!

Shaughnn · 02-24-2009, 10:18 PM

Floordude,
As I understand it, it's an incompatibility between the phosphates in the gypsum and the alkali in the Portland. The primer, when correctly applied, insulates the two from contacting each other and creating the reaction you describe. Am I close to the mark on that?
Shaughnn

wopachop · 04-01-2009, 05:57 PM

hello again good people thanks for advice so far.

the old vinyl floor is stuck really good in some spots....like where the screwdriver is. im using a dremel multi max with the scraper blade and thats not even working. a manual scraper and hammer is pulling up the lightweight concrete.

can i apply the liquid latex primer as seen in the pic or does all glue and the grey color vinyl backing need to be completely removed?

also the lady is going with pebble stones on the floor. would you fellas still use a membrane and slc im wondering if the floor still needs to be dead flat. its a little 5x6 bathroom.

thanks!!

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wopachop · 04-01-2009, 06:00 PM

EDIT: sorry this question was dumb so i erased it....peace

wopachop · 04-08-2009, 06:58 PM

ok how about this....haha feel free to rip on me i sure do loves to learn.

instead of using a sheet membrane on the floor can we use some left over red guard?

i guess the surface would be lightweight concrete---liquid latex primer---redgaurd---feather finish---thinset and tile.

whats up is that just a retarded to even consider redgaurd as a floor membrane?

WooldridgeCons. · 11-02-2009, 08:48 PM

ok.. You need to get off the keyboard and start scraping that crap up with a razor blade..i can do a 100 square foot kitchen in about an hour, but if your fat or lazy it could be something to rent out to a laborer(cornerofhomedepot).
I prefer a nice steel handled 4 inch blade. should do the trick, then the left over residue not acceding 32 of an inch in hight. could be thinset over. or lvled or wtvr the f

you need.but you gatta use something better than a f-

screwdriver bro. Btw i had to register just to say that....

WooldridgeCons. · 11-02-2009, 08:50 PM

put on atleast 6 coats and be easy on it with the trowel you should be fine...