You can go over the old tile if everything else around the floor will allow for the extra height. Because it is ceramic, I would remove the gloss with a light sanding. We would then add a latex bonding agent to the thin set. Your home improvement center can help you here. If the tile must be removed, you can stop at the cabinets keeping in mind that you are now a little higher than the counter. A new backer board is required if the old one is in bad shape or if the cermic tile is cracked.
Backer board is not as important on the wall because it is not walked on. Slate can be harder to clean because of the uneven surface so a good sealer and a top coat will help.
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Bart Blainey, B.E.R.
Consultant/Journeyman Carpenter
Building Envelope Specialist
Master Renovator
provip@prodeck.org
http://www.prodeck.org
Barton Blainey (provip) specifically assumes no legal liability or responsibility for the accuracy, completeness or usefulness of any information or process disclosed. The above further expressly advises that any use of or reliance upon the information and or opinion disclosed is at your risk .
_________________________
Bart Blainey, B.E.R.
Consultant/Journeyman Carpenter
Building Envelope Specialist
Master Renovator
provip@prodeck.org
http://www.prodeck.orgBarton Blainey (provip) specifically assumes no legal liability or responsibility for the accuracy, completeness or usefulness of any information or process disclosed. The above further expressly advises that any use of or reliance upon the information and or opinion disclosed is at your risk .