Tiling Over Painted Concrete [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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john curry
01-29-2014, 08:57 AM
Newbie looking for advice.

I have a screen porch with a concrete base. The concrete was painted over with one part epoxy paint. I will be having the porch made into a 3 season porch and I want to have the floor tiled.

Is there any special concrete preparation I should be aware of? I was told a good power sanding with 80 grit sand paper should prep the surface properly.

I will be hiring someone to do the job. I just need advice to be sure the concrete with the epoxy paint on it is properly prepped to hold the thin set.

Thanks all.

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01-29-2014, 09:19 AM
Welcome, John. :)

Mechanical removal of the paint is what you want and your sandpaper may or may not do the deed. You'd just hafta give it a try to know for sure.

I would recommend you first use a long (10-foot) straight-edge of some sort to determine how flat your concrete surface is before you start. You may find that you'll need some more serious grinding on the high spots and that would require different equipment than the sandpaper.

But if you're hiring the work done, you might first wanna have a discussion with the prospective contractor to determine how he plans to prep your floor.

My opinion; worth price charged.

john curry
02-02-2014, 01:29 PM
Thanks for the help.

I did stop at a well know tile shop and discuss the issue with them. One of their comments was well the tile will set up in the thin set and if it did not properly/fully adhere to the epoxy pained floor it was not an issue. Not an issue as the weight of the floor would not allow it to shift and worst case there might be some hollow sounding spots where the thin set did not adhere.

Please offer you opinions on this.


02-02-2014, 02:21 PM
That's some BAD advice. Not only will the floor likely debond and sound hollow, but you'll end up with cracked grout and tiles, with tiles eventually coming off the floor. Is said shop gonna pay to have the tile replaced when that happens?

Like CX said, you'll likely need to get more aggressive than a sander with an epoxy paint. More likely a 7" grinder with a diamond wheel will be needed to get back down to clean concrete. I would hope whoever you hire would have this setup in their arsenal.

02-02-2014, 02:47 PM
Please offer you opinions on this.Sorry, can't. Official Hostess and Event Coordinator, aka Boss Marge, doesn't permit the use of profanity, not even the more useful and descriptive ones, here on the forums. :)

'Bout all I can offer is that if there were any fairness in the world that "well know tile shop" couldn't call itself a tile shop at all.

My opinion; worth price charged.

02-02-2014, 02:57 PM
Hey John, I am in the same situation as you. I have a 50 x 15 Florida room that someone before me decided to paint grey. I am going to rent a big floor sander that has diamond bits from home depot. I my opinion I would want to tile over fresh clean concrete, I only plan on doing it once.

Good luck.

02-02-2014, 03:13 PM
Welcome John.

Here's how we'd handle it...
First, ignore any advice from said "tile store", and only return to get materials if needed.

Then, rent a grinder or scarifier and get rid of the paint. Take all precautions and use all PPE as necessary. You'll want a clean slab to build up from. Don't use any chemicals to strip the paint. Once liquified, the gunk will just penetrate deeper into the slab, leavin you behind where you are now.

Then, tell us about the cracks you find. Are the sides the same height, how deep, wide, etc... some photos might help.

Next, tell us about the tile you're plannin on installing. How big, ceramic/porcelain or natural stone, etc...

Then, tell us how flat the slab is. The bigger the tile, the flatter the substrate needs to be. Industry standards range from 1/4" outa plane in 10' to 1/8" outa plane in 10' for larger tile. Truthfully, the closer to perfectly flat you get, the better no matter the tile size. :)

After we get this far, we can discuss how to start puttin it all back together. :)

02-02-2014, 03:14 PM
I did a similar job about a year ago, the slab was stained and sealed. Took me about a day and a half with a 7" grinder to do 800 square feet. Fortunately it was outside and had a good breeze blowing through, cause the dust was horrendous. I wouldn't have dreamed of tiling over what was there, even if it was inside.

john curry
02-02-2014, 08:00 PM
Thanks for the advice.

I am not wanting to learn how to do this job. I will be contracting someone to do it. What I am trying to do is find out what needs to be done.

I have 4 quotes (two local flooring/tile places, two big box stores) and I have told each of them about the epoxy paint. To refresh all. It is one part epoxy so I do not even think it is really epoxy but an latex/acrylic formula.

So far I agree it has to be "sanded/ground" down versus just laid over. The question is how much? One of the local flooring shops I have done business with (as in trust them) has said a good power sanding with 80 grit will be sufficient. Their rough quote was in the middle of the 4.

02-02-2014, 08:55 PM
John, if their "rough sanding" does in fact remove all the paint, leaving you with clean concrete that readily absorbs water, then they're correct. Problem with that is you won't know 'till after they've tried it.

My opinion; worth price charged.

john curry
04-15-2014, 02:35 PM
I have a 3 season porch. Screens during the summer, windows during the winter. It is unheated. Open on 3 side, against the house on one side. Floor is poured on the ground concrete. Concrete been down for 4 years, no cracks. This is in SC

I have gotten 3 estimates from local flooring/tile companies. One of them has raised a doubt in my mind. They said to guarantee there will never be any cracking they want to apply a "membrane" but the other two have said nothing about such.

Advice please.

Thanks in advance.

04-15-2014, 05:03 PM
John, a membrane is extra protection. I try to talk folks into a membrane on all my floors just in case a crack develops at a later date. But, you don't really need it if there are no cracks but in my opinion, it's cheap insurance.

Houston Remodeler
04-15-2014, 05:35 PM
I agree with Davy.


1- Make sure there are expansion joints at the proper intervals
2- The tile to house joint is caulked not grouted
3- A tile with a little grip would be good.

04-15-2014, 08:13 PM
AN instructor I had recently said there were two kinds of concrete slabs: those with cracks in them and those that will get them later. FWIW, the expansion rate of a typical tile verses concrete is different by about 2:1. While the temp of the two will track often, it can be quite a bit different when the ground is cold and it gets bright sunlight on top...thinset is only slightly flexible, a good uncoupling membrane is VERY flexible, and can relieve any possible stresses in the install as long as you abide by proper methods.

Lots of tile survives outside without one, but it is good insurance.

04-15-2014, 09:23 PM
John, membrane it with an uncoupling membrane of choice. Do not use a membrane that has a MVER limit or an RH limit.

john curry
04-16-2014, 07:02 PM
Thank you all for the advice/suggestions.

I did question the one flooring store and a home building site manger friend about the membrane. Their bottom line was if you want to do it right and not worry about cracking then the membrane is highly recommended. I also questioned one flooring store that had quoted me I have used before. They said that in SC, moisture/freezing/cracking is not an issue so a membrane is not needed.

All they are doing is confusing me.....LOL

Having given this some thought, I have decided to simply carpet the screen porch with outdoor, self adhesive carpeting squares. It is a fraction the cost of tiling, any idiot (as in cheap labor) can lay it, and if every year or so some of the pieces have to be replaced, then so be it. After all, it is an occasionally used screen porch, not a room in my home.

Again, thanks to all that advised.