Need advice for porcelain tile install (control joints and more!)

[Wakesurfer]

Hello everyone! I am reaching the latter parts of my garage project - 75% done with 60% left to go!

I have a 30 x 45' garage with concrete finished floor that I plan to tile. I am going to check and map out any low spots in the next few days, but the floor does slope to two drains equally spaced and centered on the floor (approx 1" slope from wall to drain over 15'). I got a good deal on some lightly blemished 16x16" porcelain tiles with a PEI of 5. The tile supplier is recommending (and sells) C-Cure 907 medium bed thinset. They also recommend using a fiber mesh and epoxy kit (not sure of the brand yet) that comes in a 25' kit to mitigate the control joints. Here are my questions for those who have experience with garage tile:

1) What results have you had tiling over control joints? I have found conflicting opinions. Some say you MUST respect the joint and others say that a control joint treated with a membrane is durable as long as the movement is only lateral. The problem is that I originally was planning epoxy and the contractor cut the control joints irrespective of any tile dimensions. Also, I'm sure his lines are not 100% square!

2) How does C-Cure 907 compare to other thinsets?

3) The tile is not rectified, I was thinking of 3/16" or 1/4" grout lines - opinions?

4) I was planning on using a 1/2" notch trowel (back-buttering of course!).

5) If I can verify/correct the floor flatness to 1/4" in 10' (understanding that essentially I have two VERY shallow cone shaped slopes leading to the drains), will the lippage be reasonable using the 16x16s?

6) Any sage advice on layout strategy? I am planning a simple straight lay pattern.

Thanks in advance for ANY advice! The advice and guidance I have received on the electrical and lighting forums have helped immensely.

 

[gregtwojeeps]

You have left out the most important part for the readers to know before they can answer. How much experience do you have installing porcelain tile floors ? Good luck on your project !

 

[Wakesurfer]

Doh! Sorry... I have never done a project this size before, or worked with porcelain. I have done numerous smaller ceramic tile jobs, but they were all interior home projects - never over cement. I'm definitely no pro, but I'm very mechanical and try to research as much as possible to negate my ignorance! I don't need the floor to be perfect, but I do want it to look good and be durable. My biggest problem is that I work slowly because I try to make things perfect. I am the guy that has to have the inside of the electrical panel look good and have all my plumbing supply lines be perfectly level and square!
Do that help?

 

[gregtwojeeps]

Doh! Sorry... I have never done a project this size before, or worked with porcelain. I have done numerous smaller ceramic tile jobs, but they were all interior home projects - never over cement. I'm definitely no pro, but I'm very mechanical and try to research as much as possible to negate my ignorance! I don't need the floor to be perfect, but I do want it to look good and be durable. My biggest problem is that I work slowly because I try to make things perfect. I am the guy that has to have the inside of the electrical panel look good and have all my plumbing supply lines be perfectly level and square!
Do that help?

As one that has basically the same experience as you, I am now laying porcelain in my one car garage which is 12' x 24". You are getting ready to do a 30' x 45' garage as your first job ? WOW...

I just have this to say, the pros make it look easy and it is not. I could type a 3 page document on what to do and not to do, but will not. You can read all the stuff on here on how to, watch all the You Tube videos like,
" Porcelain Tile Projects Made Easy", but until that trowel scrapes across the concrete with the thinset under it, you will never know what you are getting in for....

Remember, brick and tile are two building materials that are basically
" unforgiving". Meaning crooked joints, uneven surfaces, tapered or uneven grout lines etc... can't be easily fixed with caulking or bondo. They are permanent eyesores unless jack hammered out and re-done. Proceed with caution and good luck to you. jmo

 

[dewalt378g]

I don't tile garages, but I have put down lots 'O tile (kitchens, baths, showers, basements, etc). So I'll try to help you best I can.

1) Post cut control joints only go through about the top third or so of a slab. Technically, it is still one monolithic slab so you should be able to tile over it. Control joints that you absolutely do not tile over are the ones that go completely through the slab such as with expansion joint, foam, or wood joints. Those are essentially separate entities which will move and expand independently, thus should be tiled separately.

However, when tiling large areas you should have a control joint for the tile itself. Depending on your tile and conditions you control joint should be every so many feet.

2) Have not used C-cure, but from it's spec sheet it looks to be what you need. For me it's Custom Building Products and I like Flexbond. I use it for almost everything.

3) For non rectified those grout lines are good. Any less and you may find yourself squeezing tiles or the pattern running out on you. Break down your installation into quadrants and you'll be fine.

4) Half inch trowel is good, but check your thinset requirements to be sure. Get a good low speed drill and mixer....you're going to go through bags and bags of thinset for this job.

5) This can be a tricky area for big tile. Farther from the drain is managable. As you get closer things will get worse. Dry lay you tile near the drains and see how bad the transitions are. Sometimes you are forced to cut the tile into sections in order to follow the radial pitch to the drain.

6) Layout is one of the most important parts of any tile job. You need to find a happy medium between the limits of the room and where the joints may (or not) fall at the drains.

For the whole room; avoid having less than half of a cut tile at the walls. If need be favor one side giving the most viewed areas the fullest tiles.

For the drains; Ideally the drain would be at an intersection of a grout line lending pitch to the surrounding tiles (for large tile format or tiles larger than the drain grate/housing). For a garage I wouldn't be so crucial and it will be your call on whether you need/want to section the tiles to conform to your pitch local to the drains. I would also snap a quadrant in the sloped areas so I know that I'm staying on course with the pattern and the rest of the job/room.

When I do large area jobs I like to lay out (DRY) a set of tiles in a straight line and spaced appropriately. I then measure this run of tile and use this larger measurement to see how they will fit in the room. It's a more realistic way of seeing where the tiles will end up as oppose to calculating tile width plus joint width and dividing it into the dimensions in the room.

Oh btw I'm a little OCD too and this job isn't going to do you any favors. Drink your chamomile tea, have your zen moment, then get to tiling.....

 

[Gerald O]

I don't tile garages, but I have put down lots 'O tile (kitchens, baths, showers, basements, etc). So I'll try to help you best I can.

1) Post cut control joints only go through about the top third or so of a slab. Technically, it is still one monolithic slab so you should be able to tile over it. . ..

No offense, but this is bad advice. Control joints in fact typically do go all the way through the slab. That is because they do what they are designed to do: control the location of shrinkage cracking. While the fresh cuts may only go down an inch or so, when the slab cures and shrinks cracks will almost always develop at the control joints. Unless the slab is held together with a good amount of rebar, there will usually be some movement at the control joints eventually. Even with rebar, while there may be no vertical displacement between sections, there can be changes of slope angle at the control joint if the sections settle differently.

Best practice is to add tile movement joints at the control joints.

 

[Wakesurfer]

Thanks for all of the advice - keep it up! I'm all ears!
Especially props to Dewalt378g, that was an awesome and thorough reply. You must be a faster typer than me. That was very appreciated and is what makes this site so useful!

 

[dewalt378g]

I have to say that Gerald is correct and makes a good point. Though, in the past, I've had success with tiling over joints such as this as well as established cracks up to 1/8" or so. I didn't blatantly (nor was I suggesting) tile over the cracks. I used a crack isolation membrane similar to what the OP intended to do. So I based my answer to the question on that information as it seems he has investigated this issue already prior to posting here.

However, what I did fail to consider was the age of the OP's slab. My isolation work was done on very old concrete (20 years or more) that was well settled and I always try to verify for movement if possible(HO history, physical measurements). For newer concrete I would agree that tiling over the joints would be a bad idea as the concrete would indeed shrink and move.

My apologies for my, "This is bad advice." as it was originally written. Also, my apologies to the OP for being misleading in my efforts.

 

[Gerald O]

For smaller areas you can get away with decoupling membranes alone, but a 30' x 45' garage slab is pretty big. One possiblity would be to divide that into approximately 15' squares with tile movement joints. If the tile joints can't be made to line up with the concrete control joints a decoupling membrane could allow the tile to span the control joints.

 

[Wakesurfer]

All good thoughts! I am going to do my best to line up as many control joints as possible, but I know that it won't work for the majority of areas. I was thinking of using the decoupling membrane as Gerald O suggested and run a silicone bead (in lieu of grout) in-between each "zone" that crosses the membrane to act as an expansion joint of sorts. Kind of like one would do where two tiled walls meet. Good idea?

 

[dewalt378g]

Yes. Make sure you don't have any thinset in your joint as well. You can also use a manufactured expansion joint, but chances are that you will have an easier time finding color matched silicone grout caulk.

 

[OJ Bartley]

I just have this to say, the pros make it look easy and it is not... until that trowel scrapes across the concrete with the thinset under it, you will never know what you are getting in for.

I wholeheartedly concur with this! I just started mine on the weekend as a first time tile project, and I got about half as much as I expected to finished, and made 3 times the mess I anticipated. The bright side is I learned a lot already and in that small time (21 tiles... yep, that's as far as I got) I got a lot better at it. Go slow, be careful where all your slop thinset goes, and do lay everything out first for spacing.