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Surface Preparation

Brick Walls

Brick walls are a strong, durable, and tile-friendly substrate when they are prepared correctly. Most problems when tiling onto brick are caused by weak mortar joints, excessive porosity, moisture, or uneven surfaces. Brick is rarely flat or consistent, so preparation is essential to achieve proper adhesion and a professional finish. This guide explains how to assess, prepare, and prime brick walls safely before tiling.

Minimum requirements before you start

Brick walls must be solid, dry, clean, and reasonably flat before any priming or tiling begins.

Stability

  • Bricks and mortar joints must be firm with no movement. Tile adhesive cannot compensate for loose bricks or weak mortar

Dryness

  • Brick must be dry before priming. Moisture trapped in brick leads to debonding, efflorescence, and long-term failure

Surface condition

  • Brick faces must be free from dust, coatings, and contaminants that prevent bonding.

Quick checks that tell you what prep you need

Identify the brick type

  • Clay bricks and face bricks are generally dense and lower in absorption and tile well when primed correctly.
  • Cement stock bricks and maxi bricks are usually highly porous and uneven and require sealing and patching before tiling.
  • Plastered brick walls should follow the Plaster and Skimmed Plaster guide, but the strength of the brick beneath still matters.
  • Painted brick walls must be sanded and slurry primed in line with the Painted Walls guide.
  • All brick types can be tiled, but preparation depends on porosity and surface condition.

Mortar joint check

  • Tap mortar joints with a key or screwdriver. Solid joints are acceptable. Hollow joints must be raked out and refilled. Crumbling mortar must be repaired with new mortar. Weak joints lead directly to bond failure.

Brick stability check

  • Press firmly across the wall. Any movement indicates a structural issue that must be repaired before tiling.

Moisture check

  • Look for dark patches, efflorescence, mould, or damp smells. Brick must be dry before priming or tiling.

Flatness check

  • Brick walls are often uneven. High spots must be ground down and hollows filled or skimmed. Tiling over uneven brick wastes adhesive and causes lipping.

Preparation steps for suitable vinyl

Clean the brick surface

  • Brick surfaces hold dust easily and must be cleaned thoroughly. Dry brush the wall to remove loose dust.
  • Remove mortar smears and high spots using a scraper or light sanding. Washing the wall with clean water and mild detergent is recommended where possible.
  • Rinse well and allow the wall to dry fully.

Remove contaminants

  • Any paint, bitumen, whitewash, old sealers, oil, mould, or similar contaminants must be removed by sanding, grinding, or stripping. Tile adhesive will not bond to contaminated brick.

Assess brick porosity

Perform a simple water drop test by sprinkling water onto the brick surface.

  • If water is absorbed within one to two seconds, the brick is very porous and requires sealing.
  • If water absorbs slowly over ten to fifteen seconds, the brick has normal absorption.
  • If water beads or runs off, the brick is sealed or coated and must be mechanically prepared and slurry primed.

Priming brick walls

Priming controls suction and ensures reliable bonding.

Standard bricks

  • Apply Kwik-Key diluted 1:1 with water using a block brush, roller, or spray. Allow the primer to dry fully.

Very porous bricks

  • Apply one coat of neat Kwik-Key and allow it to dry. If the brick still absorbs water quickly, apply a second coat. This prevents flash drying of the adhesive.

Sealed, painted, or resin coated bricks

  • Sand or grind to remove the coating, clean thoroughly, then slurry prime to create a cementitious bonding surface.

For the correct slurry mix and application method, refer to the article

Kwik-Key Slurry Guide
  • Diluted primers are not suitable for vinyl surfaces.

Levelling brick walls before tiling

Brick walls are rarely flat and must be corrected before tiling.

  • Deep hollows should be patched using a suitable plaster repair or skim coat.
  • Thin areas may be built up carefully, but tile adhesive must not be used as a levelling compound.
  • High spots should be ground down.
  • Severely uneven walls may require a full skim coat or a thin render of approximately 5 to 10 mm.

A flat substrate reduces adhesive consumption and prevents tile lipping.

Coverage rules

  • Brick surfaces are uneven by nature, so high coverage is essential.
  • Aim for at least 95 percent adhesive coverage across all tiles.
  • Lift tiles frequently during installation to confirm full contact and proper ridge collapse.

Movement and joints

Brick is rigid, but buildings move.

  • Movement joints are required at perimeter edges, ceiling junctions, wall corners, doorways, changes in material such as brick to plasterboard, and every 3 to 4 metres along long walls.
  • Fill joints with a flexible sealant. Do not grout movement joints.

Never tile over these brick conditions

  • Stop and fix first if the brick is damp or wet, mortar joints are weak or hollow, bricks move when pushed, the surface remains dusty after cleaning, paint or sealers have not been removed, primer has not been applied or was absorbed instantly, the wall is severely uneven, brick is crumbling or soft, efflorescence is present, or slurry priming was required but not used.