Why mortar under backerboard

If anything happens then the particle board will swell and ruin the tile. You can rent a toe kick saw if you need to get under the cabinets.

Link to instagram video about removing vinyl subfloor. You can also install backer board, like you mentioned, but then the floor height is going to be a lot higher than it currently is and you could have issues with door heights, etc.

Thank you for a great forum. I am replacing 20 year old 8X8 ceramic tiles in our 80 sqft kitchen installed on gypsum. When I removed the old tiles and gypsum, OSB board revealed random spots of dried mold especially under the refrigerator.

Apparently the refrigerator had small leaks over the years but the compressor heat evaporated the water while causing minor mold therefore we did not have any extensive smell of the mold.

Since I had a hip fracture 2 years ago, doing floor work was extremely difficult and expensive especially thin-setting multiple times between layers of the underlayments. I experimented laying DITRA first under the sink cabinet 4 sqft area and realized that 80 sqft will be a huge pain. However, my enthusiasm has been curbed when I read Hardibacker installation instructions and your recommendations that I still need to have thinset under the cement board. That means I am back to where I am with thinset mess and pain and more expense.

Second question is, Hardibacker is not waterproof unless I use Hardibacker Hydrodefense for Walls. Can I use Hardibacker Hydrodefense for floors? For me waterproofing and protecting 20 year old OSB from mold is more important. Really appreciate your advice. It sounds like you need to come up 1 inch with the underlayment. I think the best way to go would be to add plywood over the floor as it is right now.

You would have to check with the manufacturer to see if mortar underneath Hardibacker is necessary. I know Hardibacker wants mortar underneath but they are also assuming that you will be installing tile with a mortar adhesive. You can waterproof over the Hardibacker on a floor if you want. Also, on one side of the tub against the wall they installed green board.

At the back of the tub there is the Hardibacker where it joins into the open shower. I had thought to put Redguard over that section which will not receive a lot of water. Am I cool? Or should I demand it be cut to the height of the tile installation and hardibacker installed. The shower is separate from the tub.

Either thickness of Hardibacker works just fine over a floor. IUsing thinset under cement board depends on your subfloor. Over plywood I agree.. They spray a wax waterproofing on the floor. Thinset will not bond to it. Most new houses have advantic in them. You have to sand the whole floor down..

It usually dry before that and you can tell by the color change of the mortar. We put the cement board smooth side out, because for reason reason I had it in my head that thin-set was a mastic and not mortar. Am I doomed if I use thin-set on the smooth side? I have a laundry room that had a laminate sheet flooring in it. I removed the laminate to find they had put down 3 layers of it glued in various places.

It all looks to be the same so I guess it was done at the same time. I finally got this up and find the glue is not coming up.

Can I use a cement board to give me a clean level surface to lay my tile on? However, if you have a wood subfloor then you may not be down as far as you need to be.

Typically, the flooring is over an underlayment that is on top of the subfloor. That underlayment should come out as well. It is on a concrete floor. As I said I am down to just the remaining glue. It is hard and not coming up. I talked with a contractor and he said we could do the backer board or a leveling compound. Not sure what to do as I now have a cement floor with the glue remanence on it. You could use a foam board like Wedi or a leveling compound.

The best way to get rid of the glue is to grind it off with an electric grinder and a diamond cup wheel. Alternatively, you could prime over it with a product like Mapei Eco Prim Grip and then use a leveler or even adhere tile directly to that.

I hope I have enough information to make an answer possible. We are renovating the mudroom and lav of our home. I have a contractor, but was expecting to lay tile ourselves. The contractor has removed the previous tiles, which have been cracking. If I understand correctly, they had been set over vinyl flooring with no cement board. In general, though, I trust him. Do I need to find another flooring material?

Should I limit myself to significantly smaller, or even mosaic, tiles? They are trying to tell you the best way to install them. What about door swings? Bluestone is very thick and heavy, probably has some variance in the thickness of the product, and is going to be difficult to cut and install. If you do decide to move forward with the bluestone installation, I would recommend getting a professional installer.

Hi there! I have removed all the vinyl flooring in the bathroom but there is quite a bit of old black adhesive which has been almost impossible to remove. Is that something I can leave and cover with thinset or do I need to use a self leveling product?

I have a bathroom floor to tile. I am told that the 5mm underlayment is luan plywood. The thin set bags I have seen at the big box store say not to use on luan plywood. Do I need to replace the luan with an exterior plywood or is there a thinset available for use on luan? Unfortunately, the black adhesive probably contains asbestos so caution needs to be taken when this is encountered. These can be painted over the cutback adhesive.

Then you can proceed with Hardibacker or whatever underlayment that you are going to use on your floor. Unfortunately, the luan plywood needs to be removed and replaced with an exterior plywood with a face grade of ACX. Can I put cabinets over cement board right away or do I have to let it dry just want my sink hooked up as soon as possible. I was considering using DryPly coated plywood under my HardiBoard installation. Am I correct in assuming this is OK as the adhesion of the thinsett to the plywood is not necessary?

Treated lumber has high moisture content and warps when it dries out. This product looks like it falls into this category. What is recommended is exterior grade ACX plywood. Hello, My husband and I just installed hardiebacker last night over two layers of super thick plywood. We used thinset under the boards, the proper screws, meshtaped the seams, and all boards were cut to meet properly.

The only thing I can think of is that maybe the thinset was too thin. The screws were installed deep and evenly. You might try tapping on the Hardibacker with a hammer handle, or something, and see if it sounds hollow in some spots. The floor is very sturdy and no bounce. My intention is to replace the hearth with brick veneer, so my question is, is it alright to place cement board right over the second subfloor and brick on that, or should I install ply first then backer board and brick?

The right way is probably to install the plywood first and then the cement board. You might check with the people at Hardibacker and see what they recommend. The landlord is making repairs from afar using a contractor who did not stagger all of the seams in the kitchen. Now we get to see if he uses mesh tape and thinset. The long not-staggered seam was actually the 3rd thing I noticed. There are style choices being made in the renovation which are negatively affecting my color pallet and pattern choices giving me stress but the foundation issues are worth fighting for.

Meaning, I can look down and see the ground. Such a narrow strip. Seems like he is putting the pieces on the edge in structural jeopardy. I really hope not. I am trying to figure out if any of this is worth speaking up about. Thanks for the article. I am having my two upstairs bathrooms in a home remodeled. The contractor mentioned he would put down thinnest and cement board on the floor before laying the tiles. I did ask if lose or weak plywood needs replacing as one piece when you step it dips down.

He said no as the cement board will solve it. Should the plywood be replaced? The hole where you can see the ground should obviously be patched or filled with something. Additionally, mesh tape and mortar would help to strengthen the thin piece of backer board. Hopefully, the contractor and landlord will take the right steps forward.

However, it should be mentioned that cement board has no structural value. So, your floor will have to be structurally sound before cement board is installed. The floorboard dips down about a quarter to half an inch when pressure is applied eg when stepped on.

Not sure if this was asked previously but do I need to predrill before screwing into fiber cement board? Or will it be ok grinding flush with the board and retape from there? Thanks :. You can pour levelers over properly installed cement board. Do i have enough structural support for this?

Thanks, mg. My tile installer is installing Durock on the floor of my bathroom. He is placing it over terrazzo. I saw your comment warning against placing durock over concrete. Should terrazzo be treated the same? Also, what would be the point of installing durock over the terrazzo when he can just install the tile right over the terrazzo? Durock is designed to be used with fasteners.

Your second question is a good question also. You might ask him that. I just bought an old house, and I want to install ceramic tile on the 2nd floor.

Its an osb subfloor that had the old asbestos tile ripped off. There are some slight low spots in the floor. Alternatively, those can also be used on top of the cement board. The bathroom is 8 feet deep. Are they talking about larger marble or all marble?

Would it be possible to have less underneath the tile? You can literally see through to the unfinished basement below. Someone suggested to tape over the gaps. Not sure about that. Any insight on this is most appreciated. The reason is to make them structurally sound for a tile installation and this involves removing deflection. I would like to use cement-board over the plywood floor and put an epoxy floor on top of that. Do you see any issues with this setup? How thick should I go with the cement board?

Hi, I am renovating my half-bath on the first floor currently. The existing tile was installed approx. It is sort of flexible but feels like plastic, not sure what it is. I purchased Ardex X5 and the Wedi anti-fracture waterfproof membrane. Was going to let that cure then install the penny tile and grout. Yeah just talked to my friend who does flooring for a living. He said he doesn't put thinset under. I do whatever manufacture recommends on my jobs so I can gain their warranties and I can warranty my work properly.

If my guys did that I would have them pull it up because I can't warranty it. I probably would leave it since you have adequate subfloor and either ask is next time or find another tiler.

Theres plenty of people out there that do good work that will take direction. I have never used thinset under the cement board either. The critical issue is when there is a gap between the subfloor and the underlayment. It will bounce and then the grout tends to crack. Special screws are made for this application and are coated and the threads are course for the best grip. I have had problems with guys not putting enough screws in and trying to save money and the other is using the thinnest cement board over spongey framing.

The grout will crack up right away. Putting a lot of screws in can negate the need for the thin set. Thin set is probably only essential for thin strips of hardie backer or thin sub flooring. If they are screwed down with the proper screws every spot on the hardie backer, 6"?? Both durock and hardibacker specify it should be attached to the floor with thinset.

You should have addressed this with your contract, because its a commonly skipped step. Are you referring to 1x8 boards that run across the joists diagonally? Or something similar? I have that in my residence. I've seen it in other houses. You cannot put a cement backer board over that.

Those 1x8 boards won't give a solid foundation and will flex. Over time, that will cause tile to pop loose or crack. Durock Installation Guide. Thinset is absolutely required on all hardiboard applications. As well as recommended by manufacturer. All sub floors have movement cementing the hardiboard will not allow the hardiboard to move seperate from the subfloor, it will strenghten the subfloor as intebded by the manufacturer. I have done a number of tearouts and reinstallations cayse of constant grout cracking and loose tiles entirely because the hardiboard was not installed properly.

The fact that self proclaimed tile experts decide that they know better than the manufacturer and take it upon themselves do change installation requirements boggles y mind. Not to mention the number of times ive seen people use durarock on the floor instead of hardiboard is incomprehensible.

Instructions are there for reason people. That being said keep doing you are its nothing but job security for myself. The purpose of backer board on a floor is to create a monolithic substrate By itself this joint is strong, however it is the thinsetting of the backer board to the subfloor that locks the joints together creating the monolithic substrate.

Something to remember is that just because numerous people do something a given way, doesn't make it right. Ive learned bad habits as well. Not everything a manufacturer specifies is absolutely necessary or even makes sense, but if one is in business, they owe it to their customers to follow manufacturer specifications to ensure that in the event of problems, warranties are in effect.

I don't understand why a tile setter would bypass this step I would hold contractor responsible. It matters not if this step was laid out in the contract. It is reasonable to expect a tradesman will follow industry standard and manufacturer specifications. If we had to spell out every step for every application on a job, the contracts would be as thick as the Obamacare bill! You deserve to have the job done right! Typically I will follow manufacturers recommendations but I will not thin-set under cement backer board.

If you have ever tried removing thin-set installed backer board then you will know why. You will be taking up the floor down to the floor joists if you ever want to remodel. Just screw down and tape joints like manufacturer recommends. Install a quality porcelain tile with a "flex" type of thin-set. All the problems I've seen have been when a cheap ceramic tile was used on a dimensional lumber sub-floor. Doesn't matter how well it's installed, if you use cheap ceramic over a wood subfloor you will more than likely get cracks in the tile.

As Jon said the 1x planks will almost certainly deflect more than the tile allow resulting in cracked tiled over time. CBU does not provide any increased structural support, you need the plywood. Michael Herr. Also, backer-board provides no structural strength at all. We've heard of some contractors who have been installing for years and have never used a mortar under the backerboard arguing that if you use the correct screws and enough of them there is no need for it. However, many manufacturers including, both Durock and Hardiebacker not only recommend that you use thinset under their backerboard, but they specify it and will void the warranty on their product if it's not used.

Proper installation would be to follow the manufacturers installation instructions for applying cement board to a subfloor. Thinset is going to create a solid surface under tile and prevent flexing that could lead to cracking. Using thinset between the backerboard and subfloor will create additional strength, fill in any potential gaps that exist and lessen the possibility of movement.