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TT - Substrate Preparation on Tiles

Craftsman Guide / Substrate Preparation Troweling Over Tiles & Pavers. Instructions for preparing and leveling tiled surfaces and tile floors prior to microcement application.. This guide is based on…

tomas martinsson
Updated by tomas martinsson
Craftsman Guide / Substrate Preparation

Troweling Over Tiles & Pavers

Instructions for preparing and leveling tiled surfaces and tile floors prior to microcement application.

This guide is based on Ardex A46 as a repair mortar, but other cementitious skim coats and approved tile adhesives may also be used. Ensure the repair mortar or adhesive is approved for wet rooms and moisture-resistant.

Note: On larger tiled floor areas, a thin self-leveling screed is recommended for optimal flatness and results.

Step 1: Preparation and Grinding

• Remove Silicone: Cut away all silicone and elastic joint sealants in internal corners and transitions. Microcement does not bond to silicone—remove as much as physically possible.
• Concrete Grinding (Always Recommended): Grind tiles with a diamond grinder prior to starting. This etches the smooth glaze for maximum adhesion and flattens any lipping or protruding tile edges.
• Grip Primer: Apply a high-grade silica-filled bonding primer (when using Ardex, Ardex P4 is recommended). A grip primer provides an optimal mechanical key for skim-coating and reduces the risk of tile contours telegraphing through the base coats.

Step 2: Skim-Coating and Leveling

1.
Fill Grout Lines: Fill all grout lines completely flush. Work the trowel or smoothing blade diagonally across the joints to fill them effectively without pulling material back out.
2.
Scratch-Coat the Surface: Once the grout filling has dried, lightly sand the area and apply a thin scratch coat across the entire wall or floor to make it completely flat.
Tip: Running the trowel blade over the surface just before the mortar sets completely allows you to scrape away ridges and high spots effortlessly.
3.
Final Sanding: Sand the entire substrate completely flat. Trowel as smoothly as possible from the start—repair mortars such as Ardex A46 become extremely hard and are laborious to sand down once fully cured.
💡 Crucial for the Final Finish: The key to a clean, durable result lies in meticulous substrate preparation. Because microcement builds only 2–3 mm in thickness, it will not bridge or hide surface imperfections or level variations.

The surface must be completely flat. If you can feel grout joints or ridges by hand, there is a substantial risk that the grout pattern will telegraph through and show in glancing light after the topcoat is applied.

Next Steps: Microcement Application

Once the substrate is fully leveled, sanded, and vacuumed clean, proceed to primer selection, reinforcement mesh, and microcement application:

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