Pathology of humidity. Coated walls in the building sector

Building according to the rules of the trade, conserving or rehabilitating heritage, avoiding disorders, diagnosing the causes of pathology - all these concepts must be reflected in the act of building.

The potential recurring pathology on building walls is often as follows:

• cracks with or without water infiltration ;

• soiling ;

• detachment of exterior plaster ;

• concrete spalling due to oxidation of reinforcing bars;

• mould on the inside of the walls.

Depending on the prevailing pathology (existing or future), the builder and/or client have a number of products or systems at their disposal to intervene and clad the wall.

In rehabilitation, the aim of diagnosis is to determine the cause(s) of the pathology.

In new construction, the rules of the trade, often translated into "regulations" (standards, DTU, professional rules, etc.) aim to "achieve results" while avoiding "pathology".

In standard NF P 84 401, the legislator defined four possible functions for cladding, namely :

• appearance maintenance: coatings are used to maintain the original appearance of the cladding. These are generally colorless or lightly pigmented products, film-forming or not, designed to temporarily improve water and/or dirt resistance;

• Decoration: coatings enhance or embellish the substrate by changing its appearance: color, gloss, grain size. The solutions used are pigmented, film-forming products that also act as surface protection for the substrate;

• waterproofing: the coating makes the wall waterproof. These are flexible, multi-layer systems, and in some cases, the intermediate layer includes a reinforcement: woven or non-woven fleece, or dispersed fibers;

  Note

  the word "impermeability" covers two actions: "waterproofing" and "sealing".

• thermal insulation: the cladding significantly increases the thermal insulation of the wall. These are either interior thermal insulation (ITI) or exterior thermal insulation (ITE) systems.

The question the builder (project manager and/or owner) needs to ask is: given the pathology to be treated, what are the performances and limitations of the coating selected or applied?

The aim of this dossier is to study the behaviour or deterioration of a single wall, once clad (with one of the systems described in standard NF...