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Surface Preparation

Painted Walls

Tiling over painted walls is possible and reliable when the paint is sound and the surface is prepared correctly. Most failures on painted walls are caused by poor surface preparation rather than the adhesive itself. Paint creates a barrier between the tile adhesive and the substrate, so sanding, cleaning, and correct priming are essential. This guide shows how to assess painted walls and prepare them safely for tiling.

Minimum requirements before you start

Painted walls must be dry, stable, and free from loose or reactive coatings before tiling.

Stability

  • The wall beneath the paint must be solid. If the underlying plaster or drywall is loose, cracked, or moving, it must be repaired before tiling.

Dryness

  • The wall must be completely dry. Do not tile over damp, stained, or mould-affected painted surfaces.

Paint condition

  • Only well-bonded paint can be tiled over. Any weak or flaking paint must be removed.

Quick checks that tell you what prep you need

Identify the wall type

  • Paint may be covering cement plaster, skimmed plaster, or drywall. Each behaves slightly differently, but all painted surfaces require sanding and priming before tiling. If the substrate type is unknown, following this guide will still lead to safe preparation.

If the board moves even slightly, tiles will crack or debond.

Paint adhesion check

  • Scratch the paint firmly using a key or scraper.
  • If the paint stays firmly bonded and does not peel, it can be prepared further.
  • If it flakes, chips, or peels, it must be removed or abraded back to a stable surface.

Never tile over peeling paint, old flaking PVA, powdery or distressed paint, damp-proofing paints that soften when wet, or oil- or silicone-based coatings.

Preparation steps

Sand the painted surface

  • All painted surfaces must be sanded to create mechanical keying. Use 60 to 120 grit sandpaper to remove gloss and dull the surface completely. The paint should appear matte and lightly textured.
  • Tile adhesive cannot bond reliably to smooth or glossy paint.

Clean thoroughly

  • After sanding, remove all dust. Brush the wall down, wipe with a lightly damp cloth, and vacuum if available. Allow the surface to dry fully before priming. Dust left behind prevents primer penetration and weakens bonding.

Priming painted walls

Primer selection depends on the type of paint present.

Standard PVA or acrylic paint

  • This is the most common household paint. After sanding, apply a uniform coat of Kwik-Key diluted 1:1 with water, following the product instructions.

Gloss, enamel, or semi-gloss paint

  • These paints are very smooth and dense. Sand aggressively until the finish is fully dulled, then prepare the surface for slurry priming.

For the exact slurry method, refer to the article: 

Kwik-Key Slurry Guide

Damp-proof, bitumen-based, or elastomeric paints

  • These coatings react with moisture and are not suitable for direct tiling. They must be ground or sanded back to a stable substrate, cleaned thoroughly, and slurry primed before tiling.

Coverage rules (bond quality)

  • Aim for at least 80 percent adhesive coverage in dry areas.
  • Aim for about 95 percent coverage in bathrooms, showers, and other wet areas.
  • Lift tiles regularly during installation to confirm full contact and proper ridge collapse.

Movement and gaps

  • Movement joints are required on painted walls just as they are on other substrates.
  • Leave perimeter gaps at room edges and use a flexible sealant where tiled walls meet corners, countertops, baths, cabinets, or other materials. Do not fill these changes of plane with grout.

Never tile over these drywall conditions

  • Stop and fix first if you encounter flaking or soft paint, damp or mouldy walls, powdering paint, remaining gloss after sanding, paint applied over loose plaster, silicone, wax or grease contamination, or surfaces that were not primed correctly.

These conditions can lead to cracking, hollow tiles or bond failure if they are not corrected before installation. Use our guide to diagnose tile failure quickly and identify the likely cause.