The tile may be the visible finish, but the surface below it decides how the installation behaves. Concrete absorbs moisture, plywood can move, metal can expand and corrode, and an old tiled floor may already contain hidden failures.
That is why tile to tile adhesive cannot be treated as a universal answer for every surface. Adhesive selection must begin with the substrate, then consider the tile, location, loading and exposure.
Why the Substrate Dictates the Adhesive
The adhesive must bond to two different materials while accommodating the movement between them. A porous cement screed behaves very differently from a smooth vitrified tile or steel sheet. Preparation and product chemistry therefore change with the substrate.
The MYK LATICRETE solutions for different substrates cover applications over concrete, existing tiles, metal, wood, plywood and boards.
Tiling on Concrete and Screed
Concrete and cement screeds are common tiling surfaces, but they must be adequately cured, stable and clean.
Before tiling on concrete:
- Remove dust, laitance, oil, curing compounds and loose material.
- Check cracks, moisture and hollow areas.
- Correct major unevenness with an appropriate preparation material.
- Confirm that the chosen adhesive suits the tile, bed thickness and location.
Fresh concrete and screed can shrink as they cure. Installing too early may transfer stress into the finished tile system.
Tiling on Wood Plywood and Boards
Wood-based substrates may flex with loading or react to moisture. Check the board type, thickness, support spacing, edge support and load-bearing capacity before tiling on plywood. The board must be securely fixed and approved for the intended environment.
A normal cement-based adhesive should not be assumed suitable. PUA 212® is a modified polyurethane adhesive approved for various substrates including plywood, concrete, masonry, metal and drywall boards. The board manufacturer’s limitations must also be followed.
Tiling on Metal Surfaces
Metal presents a smooth, non-porous surface and moves with temperature. It may also corrode if moisture reaches unprotected areas.
Before tiling on metal surface:
- Confirm that the sheet, deck or frame is rigid enough for the tile finish.
- Remove grease, dust, loose coatings and corrosion.
- Complete any specified rust treatment or compatible priming system.
- Check movement, vibration and deflection.
- Use a purpose-approved tile adhesive for metal.
PUA 212® is listed for approved metal substrates and provides flexibility, water resistance and thermal-shock resistance. Product suitability must still be checked against the metal type, surface treatment, tile and service conditions.
Tile Over Tile
Installing new tile over an existing surface can reduce demolition, but only when the old installation is firmly bonded.
Inspect the existing tiles for hollow sounds, cracks, loose pieces, wax, grease and coatings. Repair failed areas and clean the surface thoroughly. A purpose-approved tile on tile adhesive must bond to the existing finish and support the new tile.
LATICRETE® 315 Plus can be considered for approved tile over tile applications within its stated limitations. Also review the added floor height, load, door clearances and drain levels before work begins.
Tiling Over Waterproofed Surfaces
In bathrooms, balconies and wet areas, the membrane must be fully cured and designed to receive tile. The adhesive must be compatible with it. Avoid puncturing the membrane during subsequent work and preserve the specified movement joints and changes of plane.
Waterproofing and adhesive have different jobs. The membrane manages water ingress, while the adhesive bonds the tile.
Quick Reference Adhesive by Substrate
| Substrate | Main checks | Adhesive direction |
|---|---|---|
| Concrete or screed | Curing, laitance, cracks, flatness and moisture | Compatible cementitious or specialty adhesive based on tile and location |
| Plywood or approved board | Rigidity, support spacing, moisture and board approval | Flexible specialty adhesive approved for the board |
| MS, GI or other metal | Stability, corrosion, grease, coating and movement | Purpose-approved polyurethane or reactive-resin adhesive |
| Existing tile | Bond of old tiles, contamination, cracks and height | Approved tile to tile adhesive after preparation |
| Waterproofing membrane | Cure, integrity and system compatibility | Adhesive approved by the membrane and system manufacturer |
This table is a selection guide, not a product specification. Confirm the complete assembly before installation.
FAQs
1. Can tile over tile work be done without breaking the old floor?
Yes, if the existing surface is sound, stable and correctly prepared. Use an approved tile to tile adhesive and account for the additional height and load.
2. Which tile on tile adhesive should I choose?
Choose a tile on tile adhesive based on the old tile finish, new tile type, application area and exposure. Check the latest technical data sheet rather than selecting by price alone.
3. Is tiling on plywood safe?
It can be, provided the board is structurally suitable, firmly supported and compatible with the selected adhesive. Wet or flexible plywood should not be tiled without an approved system.
4. Can tiles be installed directly on metal?
Only with a suitable tile adhesive for metal and proper surface preparation. The metal must be stable, clean and free from active corrosion.
5. Does concrete need preparation before tiling?
Yes. For dependable tiling on concrete, the surface must be cured, clean, stable and free from materials that interfere with bonding.
6. Can tile adhesive be applied over waterproofing?
Yes, when the membrane is cured, designed to receive tile and compatible with the adhesive. Follow the complete waterproofing and installation system.
