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  1. #1
    Join Date
    Aug 2005
    Location
    Grafton, MA, but sometimes on another planet
    Posts
    568

    Default Slate tile install questions and issues...

    My client has informed me of their choice of bathroom floor tile. I thought they were going to pick a porcelain tile which was my recommendation. They chose an Ostrich Grey Indian Quartzite Slate which is cleft and gauged. I just saw the slate yesterday. It ranges in thickness from ~5/8 to 1/4" in the same tile. Controlling lippage will be all but impossible. I tried to get the technical specifications from the dealer on the stone. They did not have much of anything. I suppose I could take a sample and do some experiments with it for hardness/scratch resistance, chip resistance, water absorption, staining, etc., but its hard to reliably tell if the stuff is any good without some real specs from the manufacturer/producer. I have my doubts that it is suitable for the application. I doubt it will be easy to maintain in a bathroom environment. In general you could say I don't like this tile at all. I'm wondering about requesting the client select another tile, but I want to make some recommendations based on a porcelain tile that looks the same as this slate OR I need some way better info on how to install this stuff so that it works without call backs. Mind you I had been thinking of following TCNA RH130, RH135 or RH140 because I will also need to install an electric heat mat. Any suggestions????

    Don
    I started out with nothing. I still have most of it left.

  2. #2
    Join Date
    Apr 2009
    Location
    midwestish
    Posts
    7,201

    Default Re: Slate tile install questions and issues...

    It's possible to seal, depending. I assume there's headroom for the added thickness that's needed to set this. I have dealt with some that has been quite good to work with - decent reasonably consistent face and some that was horrible in terms of face irregularity and flakiness; sharp edged flaky. W/o having a good representative sampling of a natural it's hard to judge. About all you can do is caution to the downsides and pitfalls [incl likely higher install price] and go from there. If they are forewarned and still want....
    “I find the curiosity of our men with respect to this animal is pretty much satisfied.”
    ~ Meriwether Lewis

  3. #3
    Join Date
    Oct 2007
    Location
    Southern California
    Posts
    2,184

    Default Re: Slate tile install questions and issues...

    I installed 12" x 12" Slate in several bathrooms and have been happy with the result.

    It was ungauged so it was a little more of a challenge than with gauged. You just have to pay attention to the tile characteristics and sort to get a good fit. Have some spares.

    One thing you can do is go through the tiles and mark the highest and lowest corners and sort them that way. Then you can make a corner intersection high or low, as appropriate, by selecting from the right pile.
    HERS Rater • BPI Building Analyst • BPI Envelope Professional
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  4. #4
    Join Date
    Mar 2009
    Location
    New York
    Posts
    275

    Default Re: Slate tile install questions and issues...

    I just did a very similar install a few months ago. Obviously check deflection of floor and make sure it's suitable for natural stone. Like mentioned, advise clients as to how natural slate differs from porcelain, including in price. I used Laticrete 4-XLT to set the tile. It's a medium bed mortar so you can build up to make up for differences in tile thickness. I started off installing the thickest tiles first so I could somewhat control the max height.
    "Always dream and shoot higher than you know you can do. Don't bother just to be better than your contemporaries or predecessors. Try to be better than yourself. " - William Faulkner

  5. #5
    Join Date
    Aug 2005
    Location
    Grafton, MA, but sometimes on another planet
    Posts
    568

    Default Re: Slate tile install questions and issues...

    Guys,
    Thanks for the responses so far. A little more info in response to your responses...

    Regarding the issues of deflection. Yes, this is likely to be an issue. The bath is located on the second floor of a circa 1800 home. I have no clue as to what the framing looks like until I rip up the present floor which has to be done for the extremely poor plumbing anyway. Ceiling height is another issue. Currently, it is too low and will need to be raised just to meet minimum code. That is if I can figure out how to do it without reframing the roof...;-) I may need to re-frame the floor to stiffen it up and then put a couple layers of ply to meet deflection requirements for stone. The build up of the floor isn't going to help the ceiling height issue any nor will it help the threshold entrance level. Maybe a set of stairs into the bathroom...;-)

    Don
    I started out with nothing. I still have most of it left.

  6. #6
    Join Date
    Apr 2009
    Location
    midwestish
    Posts
    7,201

    Default Re: Slate tile install questions and issues...

    I'd be taking them a sample of vinyl so it doesn't come as too much a shock later on. )

    At min it looks as if you're adding 1 1/2", unless you put the heat under instead of in, to the fin floor elevation. Perhaps there's a way to lower framing and stiffen, perhaps not. Best get them thinking on possibilities other than their optimal choice earlier rather than latter IMO.
    “I find the curiosity of our men with respect to this animal is pretty much satisfied.”
    ~ Meriwether Lewis

  7. #7
    Join Date
    Jul 2008
    Location
    Suburbia (Washington, DC area)
    Posts
    1,935

    Default Re: Slate tile install questions and issues...

    I used some very inexpensive Indian slate in my own house.
    There were a lot of culls in the batch I bought, soft flaky slates or corners that were too thin or broken. But, I made it work just with thinset.
    On the walls it looks awesome, the varied thicknesses washed by the light is a nice effect. I picked out the flatter ones for the floor and it's pretty reasonable.
    The slate I got is extremely porous and gets soaked whenever anyone showers. I used some random sealer and that helped some, but it still gets pretty damp. It's in a guest shower that has been used a few dozen times but not daily. I still wonder whether the slate will start to show a buildup of soap or whatever and turn out to be impossible to clean. So far so good but it seems an inevitablility at some point, and I am not sure how to clean it.

    Overall, even though it looks great and was very inexpensive, I would not use cheap slate again because of the porosity.

  8. #8
    Join Date
    Aug 2005
    Location
    Boise, Idaho
    Posts
    550

    Default Re: Slate tile install questions and issues...

    My suggestion is to forget about specifications - it varies so much someone trying to tell me specifics is looked at a little suspciously.

    I order much more than needed if returns are allowed- culling cheap slate can mean 25% are culled.

    I go through every tile and sort them roughly by color and condition - some great tiles that aren't flat get used in corners and along walls, while the best are used under tables and chairs where a flat floor is important. Clients buy slate for the color, and it's hard for me to cull something with nice color to save a piece of ugly chalkboard that's physically in better shape.

    It seems slate is especially dusty - scratch coating the backs is extra important - most slate pops are a combination of dusty backs and no scratch coat.

    Out west we put down tons of this stuff - people really love it everywhere.

    The worst story I've ever heard was a contractors carpenters putting ungaged slate down like they would ceramic - the client flew in to the property via helicopter and had a cow when he saw the work - I think he fired the contractor on the spot for being stupid.
    Last edited by Don_in_Idaho; 04-14-2012 at 05:13 PM.

  9. #9
    Join Date
    Nov 2006
    Posts
    23

    Default Re: Slate tile install questions and issues...

    Along with all the other suggestions, I did a job once where i had to lay slate in a dining room under the table area bordered by 3 bands of walnut then an oak floor and then slate around the perimeter of the room. I had to wash down the slate first (looked like they took it out of the ground and put it right on the pallet) They were so uneven that I decided to lay the slate out dry first getting the thicknesses as close as possible , got the homeowners approval, pulled them up and stacked them. Then set them without having to worry about sorting through them. Worked out great, now getting the walnut bands of wood to flush up with the slate........that's another story.

    Dave

  10. #10
    Join Date
    Apr 2006
    Location
    Kiawah Island, S. Carolina
    Posts
    1,210

    Default Re: Slate tile install questions and issues...

    About a year ago I finished my own bathroom with a material called Indian Slate. It looks similar to "Chinese slate", "African slate", and "generic slate" sold by tile distributors, stone yards, and big box stores. It has been one of my favorite materials even though it is a royal pain to install. Like any other non-homogeneous stone, it is virtually impossible to determine porosity, hardness, and other properties with any accuracy. Some slate has an oily surface making it difficult to bond. The color on the surface is usually made from some soft material that has leeched into a crack and not had enough time to harden into stone. Obviously, slate can be accurately gauged for thickness, but that destroys the beauty and colors.

    As mentioned in some of the above posts, ordering extra, sorting, and dry-fitting are an essential. For my bathroom - 8x8-foot floor, 42-inch wainscot, 5Wx8Lx9H - I spent two full days sorting according to color, thickness, and degree of flatness. First I graded and stacked for color, then each color stack was arranged according to thickness, and afterwards, each of these stacks was split into two stacks: very flat and not-so-flat. The last sorting step involves "ringing" each tile. I do this with a wooden mallet. A light tap results in a definite tone or a dull thud. A tone indicates a solid tile while a dull thud indicates a tile that might be ready to cleave or break. If I can see a crack through the body of the tile, I'll hit it with the mallet until it breaks, and set the pieces next to the appropriate color pile for use as cuts. If a tile is about to cleave, I finish the split by sticking the end of a margin trowel in the opening and wedging the two sides apart. sometimes I can get two usable tiles from one (I may also try to split and tiles that are exceptionally large.

    Then I go back to the not-so-flat tiles to see if there is one good flat side. If so, I may take a dry-cutting diamond blade and grind down a portion of the back to yield a flat tile. I resort to this step because some of these tiles are just too beautiful to cull and can be used with a little "modification".

    The next step, since I incorporate curves into my designs, is to determine how many cuts will be needed. For the inside and outside corners of this shower, I needed 3/4-inch wide cuts (raw tiles were 12x12s). Because I do not like abrupt transitions between whole and sliver tiles, I use this approach: In the center of a wall, I begin with a vertical column of whole 12-inch tiles (centered over the exact middle of the wall (For this example, I am using the long back wall of the shower which is roughly 8-feet wide). Working towards one of the corners, the next vertical column is made of 12x12s, the next 12x10s, followed by 12x8s, 12x6s, 12x4s, 12x2s, 12x1 1/4, and then enough 12x3/4 tiles to go round the corner. Once the corner is rounded, the tile sizes get wider. Of course, the above is just an example and I generally have to fudge some of the columns to get everything to fit. I always seem to work this way when tiling walls with stone.

    When making the cuts, I determine how many of each size is needed, and cut the widest tiles first, using the off-cuts for the more slender pieces. I also try to use up any broken tiles, or get flat cuts from twisted tiles that may be flat on a portion of its body. I try to cut all the pieces together - as a single step - to save time. When all the pieces are cut and stacked according to size, I lightly round over the cut edges with a bench-top belt sander, and when all the tiles are rounded over, I scour off any excess dirt or crud, rinse each tile in clean water, and allow them to dry in the sun.

    I float a mortar bed base and allow the mortar to cure for a day or two, and then use lasers to guide the placement of the tiles (I don't use layout lines on walls anymore). By this time, with all the tiles cut and sorted, it is a matter of selecting the right color to fit in with neighboring tiles. I use a latex thinset mortar and when all the tiles are set, I let them harden off for two or three days. To make consistent joints and to eliminate as much lippage as possible, I run a tile rubbing stone back and forth along each joint to bevel any high spots. This does remove some of the color, but it results in a smoother surface that is easier to maintain. When this is done, I vacuum off the dust, grout with a latex grout, and give the grout three or four days to dry out.

    To protect the surface color, I apply a liberal coat of penetrating oil (Watco or whatever is locally available) and following the application instructions, wipe off the excess after the appropriate amount of time. The oil goes over everything: tiles and grout. I wait about 4-hours, apply a second coat and let the whole thing dry out overnight before putting the shower into use. I have been installing soft, colored slate like this for years, and as long as the end user re-applies some penetrating oil at reasonable intervals, the color should last a lifetime.

    When I build a shower, a second showerhead on a flex hose is always included so that after each use, soap and shampoo film can be rinsed off. My shower does not have a door, and with a pony wall on one side, 10-foot ceilings, and a powerful exhaust fan, there is never a problem with mold. One last point, my shower has two built-in shelves both made from slate. I do have to be careful about keeping bars of soap in a dish: otherwise, soapy water dripping off the shelves tends to collect on the shower floor, and if I don't rinse the shelves, a white deposit will begin to appear on the floor.

  11. #11
    Join Date
    Apr 2012
    Posts
    259

    Default Re: Slate tile install questions and issues...

    michael,
    thanks for the informative way you handle slate tiles. I have only had a job where we did a small entry way with them and found it very frustrating to get it evened out. The sorting was the only way to go and I still found myself back buttering some tiles more than I thought I should have.

    Funny thing was when it was done and I was happy with it the customer commented that it looked a little more finished than she thougth. She was hoping for a bit more rustic or rough look she said while I worried about trip hazards and such.

    Never heard of "riniging" a tile before. Are you doing that for every type of tile or just the ones that look suspect?

  12. #12
    Join Date
    Jan 2012
    Location
    Chicago area
    Posts
    14

    Default Re: Slate tile install questions and issues...

    Don,

    I think some people want to show the differences in the tiles, it underscores the ruggedness of the material. They don't want the slate cleft matched for size. The overall thickness should be some what consistent, and wider grout joints are used to transition from one piece to another. If used in a bath room, be sure to seal. The unsealed slate will absorb urine, and the odor is extremely difficult to remove.

  13. #13
    Join Date
    Apr 2006
    Location
    Kiawah Island, S. Carolina
    Posts
    1,210

    Default Re: Slate tile install questions and issues...

    Mbeezo:
    First saw this done in Spain. Works on any tile: stone or ceramic. I have gotten used to doing it for every stone tile because it saves work and frustration - especially on some "rough" stone tiles.

  14. #14
    Join Date
    Aug 2010
    Posts
    18

    Default Re: Slate tile install questions and issues...

    First off, all of the replies so far have been accurate and informative. I just finished up two rooms (entry and bathroom) with Quartzite (slate) sourced at Daltile (China sun). A few additional comments, if I may. To aid your grout clean-up some people may wish to "preseal" the tile with whatever you are using as a sealer. It can be difficult to clean the grout from a high porosity surface (your call). Also, don't preseal at the grout joints. Personally, I like the look of a little grout in the stone, ala travatine,etc.
    When grouting, especially a floor, work only a small area at a time......it's slow but you'll be able to control the grout better.
    As for sealing, I like Sealer's choice Gold.............it's a Matte finish and seals well. If you want a "wet look" seek out some other brand.
    I wouldn't even think about doing a floor like this without first laying down a layer of Shluter Ditra.
    Bob

  15. #15
    Join Date
    Aug 2004
    Location
    Washington, DC
    Posts
    32

    Default Re: Slate tile install questions and issues...

    As a carpenter I love working with slate, it cuts fairly easily without needing a wetsaw setup(diamond blade in skil saw, diamond blade on grinder).

    I try and cull for even edges as best I can, when I go to the tile store they have about 30 kinds of slate, the more expensive the more uniform the edges(some are pretty much all perfect).

    When working with the cheap slate, as in the least expensive one they have, the trick I've found that works great is if I have a big difference in height that I couldn't avoid by culling (ie. had no extra stock left evne to use) I can beltsand or use the random orbital sander to sand the edge down and flush things out. I find using an 60 or 80 grit in a small beltsander, ie. not powerful at all one like the small PC or a 3" ryobi, works great, done carefully it leaves no scuffs/marks. Sometimes it's easier to put some 60 to 100 grit on the random orbit to accomplish the same task. I hook either one up to a small shopvac and it really cuts the dust down. Just finished two floors of the least expensive slate and the owner was thrilled, did an hour or so of sanding in each room to get everything levelled out to where I wanted.

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