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trowel size for thinset for tile

Kim_DeFreese's picture

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I am installing a kitchen countertop using 4x4 ceramic tile. I bought a "tile-in" sink which has a 3/8" lip that I must tile up flush to. My problem is that using a 1/4" notch trowel I'm about 2/16" lower then the lip of the sink. Can I use 3/8" trowel to raise the thinset so I can meet the lip of the sink or will I run into problems with the thickness of the mortar of 3/8" filling in between the tile grout space when I push the tile into the thinset. How much contact do I need between the tile and thinset? Maybe I can make the 1/4" thinset work if I barely lay the tile into the thinset without pushing it down for contact. Any advise besides hiring a professional. Thanks for your help

(post #171109, reply #3 of 6)

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Hi Rich. Thanks for your response and your help. It's a tough one because I don't want to wind up having this tile crack on me like what happen to my neighbor across the street after she spent $3,000.00, so I want everything to be done correctly. I don't think I can router the sink in because I am using 1/4" hardie board over 3/4" plywood and I think that would ruin the integrity of the hardie board (I'm guessing, they have a hotline I can call). I think using the 3/8" high by 1/4" wide notched trowel would do the trick. It would give me the height plus I could push it down into the thinset to make sure I get the coverage that you say I need. Would I still need to back butter the tile or since the notch is 1/4" wide back buttering wouldn't be necessary? If using the 3/8"x1/4" trowel won't work I will call Hardie board and see if I can router their material. Thanks for all your help, Kim

(post #171109, reply #5 of 6)

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I am installing a kitchen countertop using 4x4 ceramic tile. I bought a "tile-in" sink which has a 3/8" lip that I must tile up flush to. My problem is that using a 1/4" notch trowel I'm about 2/16" lower then the lip of the sink. Can I use 3/8" trowel to raise the thinset so I can meet the lip of the sink or will I run into problems with the thickness of the mortar of 3/8" filling in between the tile grout space when I push the tile into the thinset. How much contact do I need between the tile and thinset? Maybe I can make the 1/4" thinset work if I barely lay the tile into the thinset without pushing it down for contact. Any advise besides hiring a professional. Thanks for your help

(post #171109, reply #1 of 6)

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Hoo bruddah. Where do I start? Okay, you have explained your dilemma quite well so I see clearly what it is you are dealing with.

Going with a larger notch is fine, but only up to a point. A 3/8" square notch trowel will be okay but it probably will not solve your problem. A even larger notch will cause other problems. Sure, you'll get to the elevation you want, but you'll not have the coverage you'll need. Whatever you do, make sure to bed those tiles. That means to push them into the thinset. Do not just lay the tile on top of the thinset; you must press, beat, bed those tiles. As far as coverage, you'll want at least 80%.

I have three suggestions for how to solve you problem. One, go with the 3/8" trowel and backbutter each tile. With a 4" tile, this is alot of extra work; besides, you'll have to spend more time getting the tiles level. Two, why not simply rout a groove into the rough top? This would allow the sink to be recessed into the rough top. You're only talking 2/16" (heh heh). Third, build up the substrate to the appropriate elevation using plywood or other material.

BTW: Given how busy everyone is, you could get it done in less time than it would take to get a professional to schedule you.

(post #171109, reply #2 of 6)

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Are you sure you got those measurements right? 4x4 tile is 1/4 inch thick and thinset of ordinary stiffness, using the 1/4 inch notch trowel should give you the 3/8 inch you need to be flush with the sink. Your 2/16 short of flush (that's 1/8 inch) leads me to think you set the tile dry to check for fit and at that point thought you were low.

If that's not the case then you could do as Rich suggested and route the sink into the substrate 1/8 inch OR you could shim the sink UP 1/8 inch and add 1/4 inch tile backer board (cut out around the sink)to the substrate and then you should come out just right. OR, you could leave the sink and substrate just as it is and trowel on a skim coat of thinset to bring the base up the amount you need, let it dry, and then tile normally.

(post #171109, reply #4 of 6)

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This is a classic example of why people should just use deck mud substrate. You can control the depth precisely.

I would lay a second layer of backer board. That way the elevation is more consistant that a hand troweled thinset by a homeowner.

(post #171109, reply #6 of 6)

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Kim, Ralph explained a solution a bit better than I. I think your best solution would be for you to lower the sink into the 3/4" plywood by routing a groove the thickness of the sink lip minus the backerboard thickness minus the tile thickness minus the thinset thickness.

So, if your sink stands 3/8" above the plywood when it is sitting in the cutout in the plywood and the tile is 1/4" thick and the trowel you use gives a thinset thickness of 3/32-1/8" after the tile is beat in, then you need to route a groove of...well, zero depth. 1/4" (tile) + 1/4" (Hardiboard) + 1/8" (thinset) = 5/8". Sounds to me like you need to raise the sink 1/8". That is if your supplied measurements are correct and accurate.

Tile cracks because the substrate is not sound. Either it moves too much, does not offer adequate support, or has failed because of a latent defect. In any case, cracked tiles are a symptom of an inferior substrate. Rarely is cracked tile caused by installation error. Inadequate preparation by the installer would most likely be the cause if cracked tiles were found to be caused by the installer.

The substrate may move because it is unsecured--lack of adequate fasteners and/or adhesive or because of unequal expansion/contraction between dissimliar materials. It may sag or flex because of inedequate strength to support or too long of a span between structural members. The substrate strength may also be compromised by a latent defect caused by water damage or severe force.