Continuing with the theme of tests carried out on different natural stone products, today we are going to see those necessary for stones used in a facade.
“Tiles for wall coverings. Requirements.” (UNE-EN 1469: 2015) is the European standard that regulates the requirements for natural stone tiles used in wall coverings for wall and ceiling finishes in interiors and exteriors.
The tiles can be fixed or suspended at any angle, as can be seen in the following image (picture 1):
A dimensional and appearance control of the tiles in the factory must be carried out for each batch supplied for a work.
In addition, within the quality control of the wall tiles, and to complete the technical sheet of this product in accordance with the CE mark, there are a series of laboratory tests that are essential (see table 1).
All tests have a validity of 10 years, except for water absorption, density, porosity, and bending resistance, which must be renewed every 2 years.
What are these tests used for?
- The bending resistance is a reference parameter to determine the thickness of the coatings. Proper dimensioning prevents breakage in the tiles due to some forces that are subjected once placed, such as wind.
- The resistance to anchors is necessary when the tiles are mechanically fixed using anchors at the edges (see picture 2).
- Accelerated aging tests or durability, which reproduces adverse climatic situations and is used to verify the ability of the stone to maintain its essential characteristics of appearance, strength and resistance:
- 14 Frost-thaw cycles (resistance to freezing), reproduces the effect of frost.
- 20 thermal shock cycles, reproduce sudden thermal changes and humidity, which can occur for example by thermal variations between day and night in certain climates.
- Sensitivity to changes in appearance produced by thermal cycles, another accelerated aging test that assesses changes in tonality, appearance of oxidations, etc.
- Water absorption by capillarity: Essential test for rocks with an open porosity greater than 1% and in areas with risk of developing capillary ascension phenomena, such as when the tile comes into contact with horizontal elements where water may be present, such as baseboards, cornices, balcony slabs, etc.
The granites in general have an open porosity and water absorption by capillarity generally very low, as well as an excellent resistance to durability, which makes them the ideal choice for the construction of facades.
Nuria Sánchez Delgado
Doctor in Geology
TECHNOLOGICAL CENTRE FOR GRANITE OF GALICIA