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Do you recommend using Mastic Adhesive on Vertical Shower Walls?
QUESTION
As a new tilesetter, I am seeing mastics becoming more popular for use on vertical surfaces such as shower walls. Premium PL is an adhesive that has incredible strength that is not weakened by wet conditions. A few tile setters told me they are starting to use Premium PL or similar adhesives in this application. What do you think of this application and if you do not recommend it, why not? It seems as though it would be incredibly strong and durable. and as long as it is applied on concrete board and a waterproof membrane and the grout is properly sealed that it would be a good choice that is easier and quicker to work with than thinset.ANSWER
ANSWER - The term mastic in the ceramic tile industry is an organic adhesive per ANSI A136.1. Type 1 and type 2 organic adhesives are to be used only in interior wall and ceilings with limited water exposure. Type 1 is more resistant to water than type 2 adhesives.These types of mastics have been used a lot in commercial and some residential applications including in showers as long as it is a type 1 organic adhesive. There is no mixing and it is easier to spread and some are non-sagging. So it is a less expensive application that allows installers to install faster.
Although mastics are not considered long lasting products. They are not going to last like a dry-set thin-set mortar that can last the life of a building. Organic mastics can be a food to perpetuate microbial growth under the wrong conditions.
Looking up your Premium PL I could find no reference to a mastic. I only saw it available as a polyurethane sealant (caulking). Urethanes do adhere to tile materials very well and they are moisture resistant. There are some urethane adhesives available in a bucket for adhering tile or hardwood to different substrates that can also act as a waterproof barrier.
If you are suggesting to use a urethane sealant in a caulking tube to adhere tile then that would suggest you are not going to get full adhesion between the tile and its substrate. That would result in excessive voids behind the tile. Industry standards require 95% contact between tile and substrate for shower applications. Excessive voids will collect moisture that can result in various types of problems.
27 thoughts on “Do you recommend using Mastic Adhesive on Vertical Shower Walls?”
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Guys at Menards in Bloomington Illinois say mastic 1 is used for shower and bath walls. I already have two walls up using it………. If tiles fall off I will return them to menards
Per ANSI A136.1-2008, Type 1 organic adhesives, commonly called mastics, is more water resistant than a Type 2 mastic. Type 1 mastics are recommended for light construction; wet requirements, which includes tub enclosures and showers or other similar areas with like service requirements. So the recommended usage language is somewhat vague.
Mastic installations are considered a lower cost installation method. The TCNA Handbook shows mastic applications in dry areas, but doesn’t show it in shower wet applications.
That said, if the tile is installed correctly it can last a long time. More important is what is the substrate that it is being bonded to? Years past they would install tile with mastic over gypsum green board. They would first apply a mastic skim coat over the entire green board surface to give it moisture protection, and then they would adhere the tile with the mastic over the skim coat. If the underlying substrate material is moisture sensitive and if the mastic is only troweled on the surface it could leave voids exposing the substrate that would be subjected to moisture that could cause degradation in the substrate.
What could work to reattach a soap dish that came off. The exposed board is in the shower. I tried loctite power grab. It’s humid today so I will give it more time to set. It hadn’t worked after 24 hours.
Traditional Soap dishes are made of a ceramic or clay porcelain body. So you have to have an adhesive that will bond to it as well as to the substrate. If your substrate is a cementitious material then a polymer modified thin-set mortar adhesive will work. Also a polyurethane or silicone sealant could work depending on what you are bonding to. Note that the silicone has to have air to cure, so make sure you don’t install it so it is air tight. After the installation you should use a silicone caulking sealant to seal around the out side of the soap dish.
Tiled a shower wall with larger tiles using mapei type 1 tile advesive, from later research I found out that was not the best option, but the project was a spur of the moment decision. I am going to give them about 96 hours to dry before grouting. Will they be dry by then?
Mastic is not the best adhesive to use and a Type 1 mastic is not to be used in wet areas. One concern would be what is the substrate made of that the tile was applied to with the mastic. If the substrate is moisture sensitive then you have a bigger problem. You will have to hope that the tile wall will not be subjected to much moisture and hope for the best.
You could use an ASTM C920 silicone sealant rather than cementitious grout and that would help prevent moisture to getting to the mastic or the substrate. Make sure all transitions are filled with the caulking too. No guarantee this will work, but in theory it could even if it isn’t an industry approved method.
Can you use mastic to outside fireplace of brick and concrete to hang up flower pots?
I would not use an organic mastic to attach anything to a brick fireplace mainly due to the higher temperatures it will be subjected to. Regarding whether a mastic is suitable for adhering to a flower pot depends on what the flower pot is made of. Generally speaking mastics do not perform as well as other products and they don’t last as long.
Can I use type 1 mastic over schluter wall membrane
I don’t see where Schluter recommends a mastic for adhering to their kerdi waterproof membrane. I would only use adhesives that are recommended by Schluter for the respective product.
I used Hardi cement board in the shower and taped the seams. Used MAPEI Type 1 to fill the seams with tape. I then found out that I could not use it to set my larger format tiles. Question. I know that the adhesive can not be used over aqua defense but can aqua defense be used over the type 1 in the seam area. If so I will seal with aqua defense and then use a large format thinset to set the tile. I do not see a way to solve this problem short of tearing out all of the hardi board. Thoughts…. Also, WHY can the Type one adhesive not be used to fill the seams with tape… Knowing the WHY is sometimes the most important thing
It seems unlikely that you can apply the Mapei Aqua Defense over the type 1 organic adhesive. If it doesn’t say that is an acceptable substrate on their data sheet then it isn’t.
You should be able to pull the tape off of the Hardibacker board seems and scape the Type 1 organic adhesive off the Hardibacker board and out of the board joints. Then you can apply the membrane and bond it with a polymer modified thin-set mortar.
Type 1 organic adhesives are not a long lasting adhesive and doesn’t have the bond strength that the polymer modified thin-set mortars do.
Help! We used Maori type 1 for our shower floor. Tearing it up will mean throwing the floor tile away. If it’s grouted & sealed properly, will it be okay? For a while?
I don’t know what “Maori” is, but I assume it is a manufacturer of organic adhesives. Type 1 mastic is suppose to only be used in applications where there is intermittent exposure to water.
Depending on how the shower floor tile assembly was constructed will determine how long your mastic adhesive will perform adequately. If you have an impervious tile and if you seal the grout joints it will help to keep moisture from migrating under the tile and subjecting the adhesive to moisture. Sealers only work on a temporary basis as they do wear out. As long as water beads up on the grout and doesn’t leave a wet spot on the grout after you wipe it up, then the sealer is working. Otherwise you need to reapply the sealer.
Please help. I am very far into my bathroom renovation and now realizing i may have done something wrong. Tiling a tub surround with ceramic tile. 6mm plastic sheet over studs, durock over that, then a layer of aqua defense and membrane cloth over all the seems. I have been using Mapei Type 1 to install the 2.5x8in subway tile on the walls. I knew it was “okay” to use over durock and in tub surround, but did not realize it was not supposed to go over water proofing membrane. I am almost done laying tile finding this out. Have been using a 1/4x 1×4 trowel for it on the walls and putting a layer of it on the back of the tile before sticking it on. Have not had any tiles fall off or show any signs of movement.
We have not grouted yet. Thoughts?
Mapei’s data sheet says to use an ANSI A118 modified thinset mortar or an epoxy to as the adhesive to the membrane.
A type 1 organic mastic adhesive per ANSI A136.1 is suitable for walls in dry areas, areas adjacent to wet areas, and areas of intermittent water exposure where tile surfaces may become wet but not saturated or soaked for any period of time, and where the tiles surface will not be subject to chemical exposure.
Further it says, Organic adhesives shall not be applied over nonporous surfaces or those that have been treated with a waterproof membrane. This includes waterproofing-coated backer boards, surface-applied waterproofing membranes, and any other nonporous coating applied to the surface that is to be tiled.
I would remove the tiles while they are not fully cured and see if you can clean the mastic off of the tile and the membrane. You might have to grind the membrane off the backer board and reapply it.
Would the risk of leaving it the way it is that tiles would not adhere to the wall? The tiles are not coming off easily right now. The Mapei Type 1 label says suitable for shower walls over cement board, which is why I thought I was okay to use it. If the tiles were fully cured what would you do?
It is a personal decision as to what risks you want to take. You can leave the tile installed as is and see what happens. Maybe tiles will debond sooner than later or maybe not at all. It depends on how much moisture the mastic is subjected to.
I think that the concern is that the waterproof membrane creates a situation where under certain conditions moisture/condensation will collect of the surface of the membrane where the mastic is attached. The mastic isn’t designed to take any prolog moisture conditions. So if the mastic re-emulsifies then tiles can debond.
If you haven’t grouted yet, maybe if you use an epoxy grout that will limit moisture from getting behind the tile, but then it also might trap moisture behind the tile that doesn’t allow it to full dry that then could give a propensity to condensation at the membrane…. Or use a grout sealer over a cementitious grout and make sure it is reapplied every 6 months to a year to prevent moisture from getting in, but will let moisture out.
What is the worst case scenario for us? Tiles start to fall off the wall?
Since the mastic is an organic material that means that if it is exposed to prolog moisture it could develop microbial growth. Mold spores are ubiquitous. So if you have moisture and an organic food with warm conditions it creates a good environment for microbial growth. That doesn’t mean it will happen or that it won’t happen. That is part of the risk.
I am in the process of remodeling my bathroom. I put drywall up in my entire bathroom, even in the shower. I sealed the drywall with dry lock drywall sealer and mold and mildew resistant paint and then I did one one layer of paint that I used as a top coat for the rest of my bathroom.
Yesterday when I was buying my subway tile I was told that I can’t use a thin set mortar to apply the subway tile to the drywall, because the drywall would soak up the moisture from the thin set. So one of the employees from the store recommended that I use a mastic and just deal the grout extremely well. However I know you aren’t suppose to use mastic in a shower. So doing a little more research last night I figured I would check out a water proofing membrane. I ordered one from the same store I got my tile and mastic from. However I still have an issue, I don’t know exactly what I can use to attach the membrane to the wall. I know I can’t use thin set because of the moisture being sucked out of it into the drywall, but what I don’t know is if I can use the mastic to apply the membrane to the wall? Any help on this would be fantastic, I have a lot of time and money dumped into my renovation and I honestly don’t think I can afford to tear out anything and redo it.
For reference I purchased the schluter kerdi membrane and the mastic that I got was ACRYLPRO TILE ADHESIVE.
Thank you
First of all it is against the building code and industry standards to use gypsum dry wall in showers. It is even against the building code and industry standards to use water resistant gypsum drywall (green board in a shower). The reason why is that it will have a tendency to absorb water or the vapor from humidity and because it is a food source for microbial growth you can develop various types of mold.
Since you haven’t installed the tile, I should remove the drywall. That is the cheapest and most practical approach. Then replace it with either a Denshield Tile backer board or equal with a waterproof surface and water resistant core, or a cementitious backer board over a vapor barrier moisture bearer or over a foam tile backer board. The cementitious backer board you should waterproof, but don’t use the sheet membrane it is too problematic in how it is installed. Use an ANSI A118.10 liquid applied waterproof membrane. Caulk all of the transition joints with an ASTM C920 sealant that is either 100% silicone or polyurethane.
Then use either ANSI A118.4 or ANSI A118.15 polymer modified thinset mortar to bond the tile to the backer board, and grout accordingly.
I am regrouting a 20 year old shower area and have removed the grout between the field tiles and also removed a 3” wide deco tile band running horizontally around the shower about 5’ up from the shower floor. I found that the shower area has green board as a base. It had been painted with redguard and then the tile applied with some sort of mastic. In the 3” band, the tile mostly came off leaving the mastic intact (also some sort of paper grid work backing from the tile strip).There are several areas about the size of a quarter where the mastic came off down to a white tissue like substance. I’m assuming this is an under layer of the green board. I now want to set some 3×6” marble tiles into this opening and then regrout the whole shower. I was thinking of using a GE Advanced Silicone 2 kitchen and bath clear caulk to cover the exposed substrate (it has been tested in an area and does adhere well) and set the marble tiles. I have 2 concerns. One is the possibility of air posters in the silicone and, secondly, that the silicone will not cure under the middle of these tiles. Are these concerns valid?
I’ve also thought of painting the 3” strip with a waterproofing agent and then using some sort of mastic or thin set to adhere the tiles. Do you have any suggestions?
I have not seen any evidence of water damage or mold in the shower and all the 6×6” field tiles are tightly adhered, having 1/16” joints. The grout joints around the marble tiles are 3/16”.
Thank you for any help that you can give to me.
Green board water resistant drywall is no longer allowed to be used in showers per the building code. The reason is that when it gets wet it becomes a food source for microbial growth. So you will want to isolate that.
Not sure how thick your deco tile was, but most marbles are at least 3/8″ thick (1 cm) so you need to have enough room to install the marble. I would try to remove some of the mastic adhesive to make room for the marble if possible. I would then use the paint that area with the Redgard waterproof membrane. I would then use a polymer modified thinset mortar to adhere the marble to the membrane making sure you get full contact with no voids between the tile and the membrane.
The silicone sealant/adhesive should bond to the Redgard, but it will be difficult to do it without having voids. Plus as you suggested, if the silicone is trapped underneath the tile without air flow then it might not ever cure.
For grouting I would either use an epoxy grout as it will help block moisture from getting behind the tile to the green board. It is more expensive and more difficult to install. If you are sure that everything under the tile and over the green board is waterproof then you could use a non-sanded cementitious grout. Whatever you do, first test it out to make sure you will be satisfied with the end results.
Thank you so much for your quick reply. I found a marble tile with a beveled edge so have adequate space for it to be level with the surrounding tiles if I use the GE kitchen and bath silicone as an adhesive. I am reluctant to remove the mastic as it takes the underlying redguard and green board paper with it. The mastic area is 98% intact, so it at least gives some waterproofing. My new idea to solve the silicone curing issue to to give a skim coat of the GE silicone ( bath and kitchen) over the whole 3” greenboard/mastic strip and then let that cure for a day or so. Then apply a line of the silicone near the top edge (1/2” down) across the entire length of the marble. I would apply 2 dots of silicone on the bottom 2 corner areas and press the tile into the under layer as much as possible. This should allow a bit of air around the new silicone to cure, and a more solid seal at the top where moisture would be more likely to enter in (I think, lol).
Or, I could lightly butter the back of the tile if you think that would be better.
I’ve talked with the Mapei Tech Service department and they suggest using the Ultracolor Plus FA grout as it will fill the 1/16” grout joints in the field tiles as well as the 3/16 (plus) joints around the marble and a few other areas. I’ve used this grout before and not had a problem with the faster drying time.
Because the marble tiles need sealing twice a year, I think I will seal all the grout joints at the same time just to help with moisture control.
This “easy” regrouting job has turned onto a test of will and I should have just ripped it out and started over. But, at this point, I’m challenged to see if I can make it work for at least a few more years. A redo is one the horizon so if this lasted another 5 years I’d be happy.
Thank you for your thoughts and also for pointing out the errors in mine!!
can l use mastic to adhere vinyl wall panels in the shower
You need to go to the vinyl wall panel manufacturer and ask what they require for bonding their product to whatever the substrate is in your shower.
Mastic is general term and does not describe a specific adhesive.