How to Apply Natural Stone to Cinder Blocks
- 1). Mix the latex-modified thinset mortar according to the manufacturer's instructions. Apply a scratch coat (a thin layer) of thinset with the flat side of your notched trowel and cover the entire surface of the block wall where you will be installing your natural stone. Allow the mortar to dry completely (at least 24 hours) before you move on to the installation of the natural stone itself.
- 2). Determine your layout by measuring the size of your stones and including tile spacers between each tile to estimate the size of the tile-to-tile distances. Check those measurements against your wall to see where your starting points are. As a general rule, full tile is preferred on outside edges with cuts on any inside corners, as long as they are larger than three inches. Full tile at the floor is preferred if possible, with cuts against the ceiling, or full tile to full tile if you are not concerned about the finished height. Adjust these measurements as necessary, and draw level and plumb lines on the wall with a pencil and your level to use as a reference point for the installation itself.
- 3). Install the natural stone. Start at the bottom and work your way up, checking the overall levelness of the installation every two or three rows as you work your way up the wall. Apply a layer of thinset mortar to the wall with the notched end of the trowel, and ensure that it is evenly applied across the entire surface. Use your level and plumb lines as a "smear" reference, and avoid applying thinset beyond those lines.
- 4). Press a piece of natural stone into the mortar and apply pressure while moving the stone slightly in all directions. Repeat this process for each individual piece of stone. Use tile spacers between the natural stone pieces for grout joints. If applicable, check for plumb as you work your way up in addition to checking for overall levelness. Allow a minimum of 24 hours before grouting the installation.
