When researching building a hearth pad, I thought I read that slate needed to be sealed. When I was at home depot, this same employee, told me it didn't and I did not see any sealer for sale by it. I am not feeling quite confident in his answer and need to research more on it. We bought slate tiles. They do flake but no one is going to be walking on it. Been a busy couple days away from the house. Need to sit down and do some reading today.
My suspicion from your post is that you bought the 99 cent per square foot slate from home depot that comes in multiple colors.
Nothing wrong with them really. I have used countless square foot of those tiles and I also have used some of them in my entry way at my own home.
Some key points when working with those.
1. Be very rough with each one. I'm talking try to flex them, shake them, bend them, do everything you can to get them to break before you lay them. You will probably break about alot of them. Home depot will exchange all the broken ones. If you thin set them down and they are weak you will have a mess on your hands. Even not being walked on I would still do this.
2. Break off all loose flakes of slate before you install or seal them.
3. Use a good trowel. Around a 3/8" NOTCH not the V groove ones. Those tiles are not the same thickness as each other. And you will want the thickness of thinset to be able to make them flat.
Also try to avoid laying in straight lines. With the different size tiles it becomes obvious in lines.
4. 1/4" spacer or even a little larger if you don't mind bigger gaps. Those tiles are not rectified so you will have slightly different size tiles.
5. Large format thin set is what I have found best for slate even in the 12"x12" size. I don't use the added latex stuff they tell you to use. Unless my tiles are huge.
As far as sealing the tile because it's a hearth??? I can't think of any reason that you would HAVE too. Maybe some other folks have some logic to share here but I don't see a need.
With that being said. I would seal it. With a few caveats.
The sealer you get from home depot is mostly a water based surface type sealer. I have tried most of their sealers over the years and have been less them impressed with all of them. The problem is I can't find a sealer I really like for indoor use.
I still use the home depot sealer because it's just as bad as everything else and it's cheap.
The kind I use is the Tile Lab natural stone sealer.
If you put it on to thick it turns white, ruins your slate, and you have to take a stripper to remove it.
The only way I found to apply it safely is pour a little into a paint roller tray insert, use a large smooth sponge, and put on so little at a time that I have to do about 4 coats. I wipe it with the sponge until it's almost clear and then I let it sit until it dries and then repeat.
Just know that the nice shine you have when your done will disappear in a hurry with any traffic at all.
Also read the reviews on home depot and make sure you understand the problems with ANY of these sealers.
Any other questions let us know.
This will also give us the room to do a nice trim of slate around the bottom instead of a wood trim.
