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I'm buying some used grade school chalkboards to use as counter tops in our kitchen. I know this is done, as there are plenty of photos online, but the actual info as to how to install is scarce.

Is there any standard process for installing thin stone products as a counter top? What I've found out (and would appreciate having verified) is:

  • slate is fairly soft and we can cut it with a radial saw with a diamond blade (and a shop vac, natch)
  • we can smooth out blemishes with a hand sander
  • can be sealed with mineral and tung oils.

And I assume: - I need a wood substrate (MDF?) - possible topped with something like hardibacker - thinset slate on top of that.

Questions:

  • do I gain much with hardibacker + thinset vs. just adding more MDF and construction adhesive?
  • is there a good technique for laying the slate down on top of the counters without snapping them in half as they are tipped down? (These aren't HUGE sheets...will mostly be 2'x4' sections--maybe not a big worry?)
  • any clever ideas for edge finishing? I was thinking maybe strips of stainless steel.
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    This is a neat idea, but I would be afraid of it cracking if I dropped a pot or something heavy on it. I'm not sure if this is an actual concern, but I remember hearing about chalkboards being brittle. – Tester101 Sep 10 '14 at 17:35
  • @Tester101 yep, that is a concern--though I assume that's the same with slate tile too. That and the main workspace--the island--will likely be done with stainless steel...so hopefully I'm reducing the odds of heavy stuff on the slate. – DA01 Sep 10 '14 at 17:47
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I would handle this as a tile countertop. Instead of small 4x4 tiles you will be working with the larger slate sheets. This means, 3/4 plywood down as a base. Cement board on top of that and then thin set to attach the tiles.

You can then trim the outsides in whatever you want. It can be wood, tile or metal. You can also use the slate cut into smaller pieces to trim as well.

Once everything is set, you should then use grout to fill the gaps between the slate sheets.

Remember, just like tile you need a good solid base; so skip the MDF and use plywood.

  • Thanks. Seems doable. In reading about stone surfaces though, they seem to use epoxies in the seams rather than grout. Do you think grout makes more sense for slate than epoxy? – DA01 Sep 11 '14 at 6:26
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We just finished installing black slate chalk boards for counter tops. We used 3/4" plywood, then used construction adhesive. For edging we used 3/8" hickory to match the cupboards.

When cutting be sure to tape the cut line and carefully support it so you avoid chipping the end of your cut.

  • Great info! I know I'm asking a lot, but if you had any photos of the process or even final result, I'd love to see them added to the answer! How long have you had them installed? Any wear/tear issues yet? Did you have seams? If so, how did you handle the seams? – DA01 Jan 28 '15 at 16:45
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I think you need to treat this almost like a piece of flooring. I disagree with using thinset. I see two problems with that. First your sheets are too large. Second the board will be so rigid that it might lead to more dents.

I would use 1/2 inch plywood like a high end granite install. Then I would glue down some foam flooring underlayment. Then glue down chalkboard on that. That will give you a firm structure but allow a little flex in your board so it doesn't get nicked up so quickly.

Also I would agree with the metal corners. If you get 1" "L"s available at big box you can just glue them in and you are good to go.

  • By 'dents' to you mean chips? – DA01 Sep 10 '14 at 20:54
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    I disagree about wanting flex under the slate. Flex is what snaps tiles in two. It is easy to spot a tile floor that flexes. The ones that flex will have cracked tiles since they flexed with the floor and then broke. There is a reason why mortar or cement backer board is used for both floor and counter tile installs. Because a thick bed of mortar or the backer board don't flex and give a solid foundation to the tile. Granite doesn't need heavy plywood and backer since they are usually 2 to 4 times thicker than tile. – diceless Sep 11 '14 at 5:53
  • @DA01 - chips is probably a better term. – DMoore Sep 11 '14 at 5:54
  • @diceless - a chalkboard is not tile. Not sure exactly how thick his chalkboards are but most I have seen are about 1/8". I can't see getting this to lay exactly flat with thinset - your tile doesn't sit exactly flat but it is more rigid and you don't notice. When talking about "flexing" I am talking about a soft surface, not "bending". I really don't get your point - thinset on plywood will flex too. You will just crack the thinset first and it will slowly compromise the structure above. My way has nothing to crack or deteriorate. – DMoore Sep 11 '14 at 6:05

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