2024-25_NTCA_Reference_Manual_dig_dwnld

Proper Bedding Procedures

stone tiles can vary depending on the type of quarrying process used. Some cleft stone materials have ground backs that pro vide a coarse and uneven surface. For some large format siz es and irregular thicknesses, it is important to pull each piece away from substrate and visually examine the mortar to ensure the proper amount of mortar contact was achieved. It may nec essary to add more mortar to any places where good contact was not made. To apply mortar to ungauged stones for an over all consistent thickness, a box screed may be used. (See Box Screed page 196.) SMALL MOSAIC TILES Installing small mosaics, keeping them flat and having enough mortar under them, without the mortar coming into or through the grout joint, can be a challenging endeavor.

First, key the mortar into the substrate using the flat side of the trowel. You will find that the notched trowel for this procedure to be deeper than you may think or expect. Next, trowel out the mortar leaving a uniform amount of material, and trowel it out several inches beyond where your first sheet will stop. Always trowel in one direction. Then, using the flat side of the trowel or a broad knife, knock the ridges down to a consistent level with out picking up any excess material (Photo #1). Then set the first sheet of tiles onto the flattened mortar in its designated loca tion and “gently” beat in the tiles with a flat wood beating block or flat rubber float (Photo #2). Contrary to beating in large tiles, the small mosaics require a gentler approach (Photo #3). Remember the size of the tiles that you are working with. Because there are no ridges to collapse, gently beating in the tiles with the flat block or float will properly embed the tiles. When you can see that the mortar is starting to protrude up into the grout joint you should have good coverage. Lift an edge of the sheet to see that you have good coverage. If the mortar is protruding up out of the joint, you are beating in too hard. These are small delicate tiles. You will get used to a gentler touch with practice. Now continue to trowel out mortar, re-notching the previous ly flattened mortar next to your previous installed sheet and re-flatten. This process will assure that the mortar is still keyed into the substrate, always fresh and will not skin over. Continue to set your sheets. As you beat in the next sheet have a portion of your block transfer from the previous sheet, beating in two sheets at once. This will keep the top of the tiles on plane and not tipping. The trowel size will be determined by the thickness of the tile and the texture on the back of the tile. Some glass tiles have a cavity on the underside that will require more mortar in order to get proper coverage. Paper face mounted mosaics are manufactured so that you get the most mortar coverage on the back of the tiles when they are installed. Because they are face mounted, they are easier to ad just after they are installed. Before starting your installation, check the sheets for size from one to the other. Because you can only see the perimeter of the sheets from the front, check the back of the sheets and check to see that the tiles are mounted square and/or correctly. If there are pieces that do not line up with others they will need to be ad justed later, or cut them out now and install them after you have removed the paper. Lay out several sheets on a flat surface in order to determine that the sheets line up from one to another. With every tile, always use the proper size trowel in order to get the proper coverage needed after beat in. GLASS TILE COVERAGE Paper-Faced Glass Mosaics

The following method can help with all of these issues:

Photo #1 shows the ridges being knocked down with a broad knife.

Photo #2 shows a thin glass mosaic that is being set and beat in.

Photo #3 shows re-notching the previously flattened mortar to keep it fresh.

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NTCA Reference Manual | 2024 / 2025

Chapter 8 | Thin-Bed Method Installations