Substrate Preparation5th February 2016
The suitability of a substrate should always be fully assessed before carrying out any tiling. The main criteria to be assessed is:
- Is the substrate strong and stable?
- Has the substrate dried/cured completed?
- Is the substrate smooth and reasonably level?
- Is the substrate porous or non-porous? A test area should be used.
If the answer to any of these is ‘no’, then the substrate is not suitable to be tiled onto and further preparation is required before priming and fixing.
Why should you prime?
Priming of substrates is key to ensuring the selected adhesive can perform to its optimum. There are three basic reasons why priming is important. UltraTile provides the perfect solutions.
- The sealing of substrates to reduce moisture absorption from cementitious adhesives enabling them to hydrate and cure properly. We recommend the use UltraTile Prime IT FP or UltraFloor Prime IT Multi-surface Primer.
- On dense and impervious substrates it is beneficial to utilise a bonding primer to enhance the adhesion of the tile to the substrate. Such substrates would include epoxy damp proof membranes, tile on tile, asphalt and painted surfaces. For this we recommend the use of UltraFloor Prime IT Multi-surface Primer neat.
- On some substrates it may be necessary to create a barrier between the substrate and adhesive to ensure compatibility. This may be when applying cement adhesive to calcium sulphates or when bonding onto substrates affected by high alkali adhesives. We recommend that UltraFloor Prime IT Multi-surface Primer is used when a barrier primer is required.
Is the substrate porous or non-porous?
General priming guidance is to use UltraTile Prime IT FP or UltraFloor Prime IT Multi-surface Primer when tiling onto a porous substrate such as sand/cement. Whereas UltraFloor Prime IT Multi-surface Primer neat should be used on non-porous substrates such as ceramic, terrazzo, asphalt and epoxy based damp proof membranes. We do not recommend the use of PVA for priming.
For underfloor heating systems in terms of priming please see specific advice guides.