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I have a screened in sun porch with a concrete floor. The floor has been painted with Rustoleum, one part epoxy, concrete paint. The paint holds well and looks good but now I want to dress the porch up more by laying porcelain/ceramic tile.
I have done such before so I know how to do and what materials to use but my concern is will the tile mortar adhere to the painted concrete. Is there any special prep to assure it will?
Ideally you would either do a full "mud bed" or use an isolation membrane and than standard mastic or thin set depending on the manufacturers' directions.
Mortar probably will not adhere to epoxy. Even if you use a "floor grinder" the membrane or mud bed will give a better result with less mess.
The mortar does not need to adhere to the painted concrete. It will sit on the concrete. There is no water flowing so it doesn't even need to seal with the painted concrete. To ease the application you could prime the surface with a latex primer. I say not needed.
Latex over epoxy-
Now, That's goin' stick. NOT!!!
And if you say it's not needed- why even mention it?
As chet mentioned- the isolation membrane would be the least evasive method to install the tile over the existing concrete's condition.
I mention it because the troweling of the mortar will be smoother if there is a latex primer. You may not be aware, but that is also the preferred method of painting vinyl tile. Latex primer first. Its like skim milk. You just pour it on the floor and roll it out and it takes an hour or two to dry. Maybe its not needed.
And, what is the point of an isolation membrane under these conditions, i.e. a sun porch with a roof over it? If the concrete is migrating, then I suppose so, otherwise it will be a big waste of money.
Last edited by Wilson513; 02-08-2012 at 12:36 PM..
And, what is the point of an isolation membrane under these conditions, i.e. a sun porch with a roof over it? If the concrete is migrating, then I suppose so, otherwise it will be a big waste of money.
Well let's see- screened in porch/patio, check.
No heating or A/C (uncontrolled environment), check
Is exposed to the exterior elements, check
Slab can, and is exposed to temperature changes which tends to lead to expansion and contraction, check
Current coating is impervious- not allowing a thinset mortar to adhere, check
Conditions right for an isolation membrane? Yes, check
Thanks for the help. One thing to add. The Rustoleum product is Acrylic based and as said, it is what they call a one part epoxy. Not sure that will change anything but let me know.
I had a similar area that was concrete not climate controled that was going to be tiled but the flor was also coverd in some type of poly-epoxy something or another. The companies I got bids froim all required that the concrete be prepped to accept the mortar. The methods they described varied but basically they would be creating a means for a solid bond betwen the original concrete floor and mortar, be it a bond between mortar>coating>concrete, or mortar>bare spots from removal of coating>concrete. The one thing they all required (or thewy wouldn;t gaurantee the tileing) was that a isolation membrane be used. Even the cheap 'handyman type" company that didn;t absolutely require the isolation memberane said they highly recommeded it because without it, the tiles and/or grout was more likely to crack.
I had a similar area that was concrete not climate controled that was going to be tiled but the flor was also coverd in some type of poly-epoxy something or another. The companies I got bids froim all required that the concrete be prepped to accept the mortar. The methods they described varied but basically they would be creating a means for a solid bond betwen the original concrete floor and mortar, be it a bond between mortar>coating>concrete, or mortar>bare spots from removal of coating>concrete. The one thing they all required (or thewy wouldn;t gaurantee the tileing) was that a isolation membrane be used. Even the cheap 'handyman type" company that didn;t absolutely require the isolation memberane said they highly recommeded it because without it, the tiles and/or grout was more likely to crack.
From what I have read the membrane is basically to prevent moisture and/or cracking issues verus make for good mortar adhesion.
Seems to me even if the mortar will not adhere to the paint covered concrete but it "molds" to the concrete surface and hardens/holds the tiles in place then the weight of the whole thing will keep it in place. Also seems to me that any real concrete cracking/settling could cause tile cracking, membrane or not. As I am in SC we do not have ground freezing/heaving so that is not an issue.
I did lay tiles in thinset on top of bare concrete to tile a porch identical to this one some 10 years ago. It looked as new/good 10 years later thus the only different issue I face now, is the mortar adhesion issue.
Of course my thinking could be off......thus I keep learning.
I thank you and all others for responding.
Last edited by accufitgolf; 02-08-2012 at 03:22 PM..
Its been awhile but I remeber the reason for the isolation membrane was because there was no way they could guarantee that the mortar under the tile would adhere 100% all the time to the floor because of the coatings residue and such. Even with some primer or bonding agent, there are too may things that can cause a failue of the mechanical bond. The membrane acted as a grid for the mortar on the tile side to create a solid mortar layer for the tile and grout to fasten too. The mortart below the memberane acted as a fastener to the concrete and memberane but in the event any area fails, it will not "telagraph" (?) through to the finsih side way better than just the grout and martar could prevent it. I guess it simply that if you glue bottle caps to a wall and a area of the glue doen;t hold to the wall, those could pop off, where if you glued them to a fibergalss mesh and glued the mesh to the wall, a failue in a small area won;t defeat the hold over the entire area. maybe someone else can explain it better cause maybe I;m not explaining it correctly under this situation.
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