We consider the proposed parameters for the complete characterisation of substrates and fixing surfaces to be universally applicable to every type of material and product. The following features have been related:
- Base substrate to stability and durability, without loss of base substrate physical attributes as the structural construction element on which the modular rigid covering is to be installed.
- Intermediate layers, also to the dimensional stability of their constituent materials: dimensional stability related to the compressibility of organic and prefabricated materials, and to the maturity of layers made with cement and/or lime conglomerates.
- Fixing surface to conditions of flatness, to key characteristics in fixing surface relation to bonding material and adhesion [texture, cohesion, absorption/suction, surface state, and chemical compatibility], and to a final characteristic, also linked to stability and durability: sensitivity to water and damp of the material making up the surface
These characteristics, together, allow the substrate to be fully contextualised in relation to the choice of materials and tile installation technique. Though the specifications writer is usually familiar with these characteristics through the different standards, such a contextualisation is often a complicated matter for other construction professionals, including all those involved in the marketing and sales of covering materials, as well as tile fixers, owing to the multiplicity of the variables involved, particularly when there are no specifications in the project technical reports.
The charts below represent a first approximation that does not, in any way, enter into the consideration of matters of detail; nor does it encompass all the types of substrates that could receive a covering.
For example, concrete building envelopes are usually not tiled, while internal building columns are very frequently tiled to match given areas. Metal formwork will produce smooth as well as impervious surfaces, owing to the intrinsic characteristics of structural reinforced concrete. Hence the need to fix tiles with adhesive, in an intermediate or thin bed.
However, structures are also subject to movements of different types and not just those stemming from structure maturity (for example, creep in concrete structures). Sometimes, those movements produce stresses with the rigid elements fitted in the structure and ensuing potential cracking at the junctures.
For that reason, when columns are tiled, the tiling needs to be performed on glass-fibre mesh that will protect the tiling from cracking, through a contact layer with deformable adhesive.
The example provided is intended to illustrate the limitations of a brief contextualisation of substrates and fixing surfaces, a contextualisation that cannot be reduced to a few synoptic consultation charts
. For that reason, it is recommended that the Reader should fill in the questionnaire on substrates