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Can Ceramic Tile be Installed over CMU (concrete masonry unit) block?
QUESTION
Can Ceramic Tile be Installed over CMU (concrete masonry unit) block? - Can I install Ceramic tile over a CMU wall?ANSWER
ANSWER - Yes you can install ceramic tile over CMU (concrete masonry unit) blocks.You need to properly prepare it to make sure it is free of any structural cracks, clean, and plumb. You can bond the tile directly to it or you can fasten metal lath and apply a scratch and brown coat of mortar.
For a direct bond to the CMU, it is recommended to skim coat it with the thin-set mortar to smooth it out prior to applying a liquid applied waterproof/crack isolation membrane. Then use a high performance modified thin-set mortar exceeding ANSI A118.4 and make sure you achieve 95% contact bonding the tile to the membrane. Then grout it. To see a list of manufacturers who produce tile installation products go to our website at www.CTaSC.com and go to the Resource and Links page and there will be a list with links to their websites. Good luck.
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Thanks great information
Do I need the membrane on an interior wall (for an office), as well, or just exterior, where there may be moisture? That stuff is expensive!
No you don’t need a membrane on the interior wall for moisture control. If you do have cracks in the CMU then you might need to apply a crack isolation membrane. Otherwise you can just grind the surface flat, clean the wall, and adjust the wall with a patching mortar if it isn’t plumb or has low spots. Then adhere the tile direction to the properly prepared CMU wall.
How are the ends of the cmu wall covered with tile? I have 6″ cmu walls to 7′-0″ tall dividing three showers so the end of the wall also needs tile. Would you recommend using Schluter edges at the outside corners ? What is your recommendation? Thank you
Using a metal profile at the outside corners of the CMU wall is one way of doing it. Although a more professional way is to do a quirk miter at those transitions. That is where you cut a 45 degree angle not starting at the top edge of the tile, but drop down an 1/8″ and cut the miter there. This way you don’t have a sharp edge at the corner.
I want to install 3/4″ 25×24 porcelain pavers as wall tile on an exterior free standing garden wall. The wall is concrete block. Can I use ditra or kerdi as uncoupling membranes?
Ditra is an uncoupling membrane and not meant for wall applications. Kerdi is a sheet membrane and it can be used on a wall substrate, but I would not recommend it.
I would grind the concrete block (CMU) if necessary to remove any high spots or lippage between block edges. I would power wash it to remove any residuals from the grinding. I would skim coat the CMU with a polymer modified thin-set mortar using the same non-sag thinset you use for adhering the 3/4″ thick porcelain pavers to achieve a smooth surface. After it cures for at least a day or two then apply a liquid applied waterproof/crack isolation membrane over the skim coated wall. Then after that is cured per the manufacturer’s directions, then adhere the tile with a non-sag thinset mortar adhesive. Start at the bottom and work up.
Considering the weight of the 3/4″ thick porcelain pavers you need a membrane that will be tenaciously attached to the CMU and a thinset that is non-sag. Having the membrane will help minimize or prevent any efflorescence.
Can I bond porcelain to outdoor heavy blocks using just a slurry primer and mortar?
Yes you can adhere porcelain tiles to concrete block units (CMU). You should first grind the surface flat to remove any high spots. If necessary skim coat it with a polymer modified thinset mortar to fill in any slight low spots. Then adhere the porcelain tile with the polymer modified thinset that at least meets ANSI A118.4. Make sure you put in movement joints every 8 to 12 feet in each direction on center.
Do you have any products that you recommend for commercial applications where CMU walls are to be clad with porcelain tile?
I assume you mean installation products.
First I would go with a single source manufacturer installation system such as Laticrete, Custom or Mapei or others that provides an extended 10 year Labor and Material Warranty or better with their system of membrane, thinset and grout.
You can grind the CMU flat and adjust it with a patching mortar to plumb it out, and then apply an ANSI A118.10/A118.12 liquid applied waterproof/crack isolation membrane over it to help prevent from efflorescence staining. More important for exterior walls, but I would do it on interior walls too.
Use an ANSI A118.15 polymer modified thinset mortar to bond the tile to the membrane. Be sure to achieve at least 95% continuous contact between the the back of the tile and the substrate. Skim coat the thinset to the back of the tile and the membrane with the flat side of the trowel to key it in. Then use an appropriate size trowel to trowel enough thinset to set the tile. Be sure to trowel so the trowel ridges are parallel to each other and to the short side of the tile. Then beat the tile in and shift it perpendicular to the trowel ridges.
Veneer tiles that debond become a life and health concern and can end up costing the installer a lot of money and time to have to fix or replace it. So don’t cut corners, and provide quality control oversight and supervision of the installers.
My basement has concrete block walls. Due to moisture and cracking, a French drain and steel support posts were installed 10 years ago. I want to finish the basement by tiling the block walls and floor (including but not limited to a shower against the back wall). I’m worried a membrane will cause more problems than it solves, but should I use one? If so, what kind? Should I use epoxy grout or cementitious? What types of tile are best?
Absolutely you should a waterproof/crack isolation membrane. As long as you don’t have hydrostatic water pressure were water is coming through the concrete then if installed correctly will provide you with waterproofing and crack isolation. Particularly the shower has to have a waterproof membrane on the floor and walls. There are liquid applied membranes that meet ANSI A118.10 and A118.12 for bonding tile to them with a polymer modified thinset mortar that meets ANSI A118.4 or .15.
Epoxy grout if installed correctly is stain proof and impervious, but it is more difficult to install and more expensive. Cementitious grout is more commonly used for tile installations. Ceramic Porcelain tiles are most durable and impervious, but there are other types of tile that can work, so it depends what look you are trying to achieve.
I’ve built an outdoor fence using 2 ccb’s stacked standing up in my yard with a quikcrete base. I live in S. Florida so plenty of moisture. I wanted to install a decorative stone-like kitchen backsplash sheet of a stone mosaic pattern completely around the exposed ccb( except the holes of course). Is there a preferred method and materials for this particular situation? Thanks for your help in advance!
I am assuming you mean CMU (concrete mortar units) is what your fence is built of. As long as the wall is structurally sound and made of concrete you can adhere the tile to the wall with a dry set thin-set mortar. If it is a porcelain tile then the thinset should be a polymer modified thin-set mortar meeting ANSI A118.4.
It would be better to first grind the CMU and patch it so you are grinding off high spots and filling in low spots with a patching mortar. The apply an ANSI A118.10 liquid applied waterproof membrane and bond directly to it. That way you can avoid effloresce staining if installed correctly.
I have an interior CMU kitchen wall that I would like to tile a backspace directly to. The top portion Id like to lime plaster. What do you recommend to smooth out the grout lines?
I am assuming you want to plaster a portion of the wall and in the other portion adhere tile to it.
You should scarify the CMU to remove any paint or contaminates. Use a dustless grinder or use a construction vacuum with the grinder to control dust. Then use a thinset mortar adhesive to fill in the joints and smooth the surface. If the wall is out-of -plumb then you might need to use a polymer modified patch mortar to building it out. Then adhere the tile to the mortar and plaster the other portion.
How do I install diva gris porcelain tile to a precast concrete basement wall? It is 5000 psi concrete, flat, with a light roughness, and no release agent applied. Do I need a scratch coat first?
First you want to make sure the wall is plumb, that it readily absorbs moisture if you sprinkle water on it, and that it is clean. If it doesn’t readily absorb moisture then you should scarify it to open up the pores and remove any possible contaminants.
If the precast concrete wall is structurally sound and it isn’t too far out of plumb, you could bond the tile directly to the properly prepared surface. If it is too far out of plumb, you can shoot in metal lath and apply a scratch coat and mortar bed. Or you could use a polymer modified thinset mortar to apply it over the wall with a notched trowel and in a horizontal direction. Then apply a mortar bed over that.
For a basement wall I would apply a liquid applied waterproof/crack isolation membrane over it as long as there is no indication of hydrostatic water pressure or excessive moisture.
I have a CMU fireplace that has been subject to a leaking roof in the past. I want to tile the interior with porcelain tile but fear potential moisture from inside the fireplace could result in tile failure. Do you have any suggestions?
First of all repair the roof leak. You probably need to add some flashing or asphalt patch to it.
Porcelain tile is technically impervious at less than 0.5% absorption so water doesn’t harm it. The polymer modified thinset mortar adhesive for wet areas isn’t affected by the moisture. The grout in the grout joints is porous and if moisture is migrating through it you might get efflorescence staining. As long as the CMU is properly prepared and the tile is properly installed it should bond adequately.
I am building an outdoor barbeque and pizza oven in central PA. The construction is 8″ CMU base with a dry stack field stove veneer over the walls. I am thinking of applying porcelain tile for the cap. The base of the cap will be 2″ thick CMU. Should a liquid waterproofing agent be applied before tile is set?
The purpose of using a liquid applied waterproof / crack isolation membrane is to make the area waterproof or water resistant and to help prevent shrinkage cracks in the substrate to transfer through the tile.
You should have shrinkage cracks with CMU other than maybe in the joints between the blocks. You probably don’t need to waterproof the CMU, but the benefit of applying a liquid applied waterproof/crack isolation membrane over the entire outside of the CMU is to try to prevent efflorescence staining. CMU has lots of minerals that forms of salt and when it gets wet the minerals dissolve in the moisture and as the moisture migrates to the surface and evaporates it predicates the minerals into a while-like residual. Depending on what your barbeque will be subjected to will depend on how big of a problem this may not be. Just applying the membrane to the top cap wouldn’t do much.
First, great comments and answers. Second, I just applied Merlex Super Blockade waterproofing to a poured outdoor concrete wall after it had cured for 25 days. I now want to install 24” by 24” marble paver tiles on the wall that is part of a fountain feature. Plan to use polymer modified thinset but wonder if I have to let super blockade cure for another 10 or 28 days?
First of all, you must always follow the product manufacturers’ directions, regardless of what I or anyone else says.
According to the Merlex Super Blockage Waterproofing description given on their website they say ” Allow Super Blockade to cure for at least 7 days before filling spas, pools and tanks”. Of course that is based on it being installed correctly and curing under dry conditions and acceptable temperatures. Colder temperatures and higher humidity will cause most products to retard the curing time.
They say this is a cementitious waterproof membrane for concrete surfaces that were properly prepared and had fully cured. They don’t mention whether you can adhere marble to the Merlex or what will bond to it. They don’t say that it meets ANSI A118.10/12 for tile waterproof / crack isolation membranes that can have tile bonded to it with a modified dry set thinset mortar meeting ANSI A118.4 or A118.15.
Chances are an ANSI A118.15 modified thinset mortar will bond to it, but you need to confirm that with the Merlex manufacturer and with the manufacturer of the thinset mortar.
Of course, if approved, you also need to make sure you properly adhered the marble to the Merlex with the intended thinset mortar. That means you need at least 95% thinset continuous contact between the marble and the Merlex, and you need to have movement joints every 8 to 12 feet and at all change of planes and materials per TCNA EJ171.