This technical specification refers to the installation of slabs on cementitious screed or plastered walls by adhesive.

1. Relevant standards

EN 12440 (2017) Natural stone - Denomination criteria

EN 12670 (2019) Natural stone - Terminology  

EN 1469 (2015) Natural stone products - Slabs for cladding - Requirements

EN 12058 (2015) Natural stone products - Slabs for floors and stairs - Requirements

EN 12004 (2017) Adhesives for ceramic tiles - Part 1: Requirements, assessment and verification of constancy of performance, classification and marking 

EN 13888 (2009) Grout for tiles - Requirements, evaluation of conformity, classification and designation

and other standards mentioned in these standards.

2. Material

The contractor is obliged to submit stone samples and manufacturer's certificates for all materials to the supervisor for approval, through the Submittal process, before procuring the material.

The samples should be the same size and thickness as the slabs to be installed. If the material is accepted, the samples are kept on the construction site until the end of the works.

If there are natural defects on the samples (such as stains or similar), they should be classified as acceptable or unacceptable. Defects that are not present on the samples cannot be acceptable on the slabs to be installed.

Slabs of the same type of stone that are installed in the same room should be from the same quarry, and in the case of smaller quantities, from the same block.

The surface of the slabs should be dull polished ("honed") with a matt finish (treated by polishing disk with grain size F.400 to produce a very flat but not polished finish). All edges of the slabs, that are visible in the interior, must be finished in the same way as the surface of the slab.

Deviations in the dimensions of the boards and their thickness, flatness and surface finish are not allowed. The angles of slabs must be 90° (unless otherwise provided by the design).

The stone slabs should meet the following minimum requirements:

Flexural strength (EN 12372): 15Mpa
Uniaxial compressive strength (EN 1926): 130Mpa
Water absorption at atmospheric pressure (EN 13755): maximum 0,5%
Slip resistance (EN 14231): maximum 50 for dry surface and maximum 30 for wet surface
Abrasion resistance (EN 14157): maximum 20mm

The supervisor may accept the material even if some of the above requirements are not met.

There are no special requirements for stone slabs that are installed on the walls.

There are no special requirements regarding the emission of radioactivity and the release of dangerous substances. The material should comply with the requirements of local regulations.

Adhesives for natural stone slabs should be cementitious, white and classified according to EN 12004 as class C2F S1.

Before starting work, the contractor should check with the stone supplier the compatibility of the adhesive and the stone, in order to avoid the situation that stains appear on the stone surface.

Grout for stone slabs should be fast drying and classified according to EN 13888 as class CG2AW. Chemical compatibility with the material of the slabs should be checked by contractor.

For impregnation of the stone, the contractor should use a ready-made water-based material that reduces the absorption of water and oil on the surface of the stone, does not change the colour of the stone and which is provided by the manufacturer for the honed stone. The material should be resistant to UV radiation and with the allowed amount of harmful (VOC) substances.

3. Workmanship

Prior to the start of works the contractor is obliged to check whether the room has been prepared, e.g.:
- whether the substrates (cement screed, plastered walls) are cleaned, without cracks and other damages and the level and flatness are in accordance with the requirements in the technical specifications for cementitious screeds and plastering works and the design.
- whether all electrical installations, mechanical installations and installations of water supply and sewage systems have been finished and tested,
- the waterproofing is completed and tested and
- frames for joinery and other equipment are built in.

Irregularities in the cementitious screed should be remedied mechanically (by scraping), by installing additional layer of levelling compound (must be compatible with the adhesive) or by thicker layer of adhesive, in accordance with the manufacturer's recommendations. Irregularities in the plastered walls should be remedied mechanically (by scraping) or by installing additional layer of adhesive over the mash. If none of the methods can be applied, the substrates should be removed and a new one made.

If the room is ready for the installation of stone slabs, the contractor should, in writing, request the supervisor to approve the commencement of works.

After the delivery of the stone slabs to the construction site, it should be unpacked and inspected for compliance with the approved samples. If, due to the large quantities of delivered stone, it is not practical to unpack all the pallets, a few pallets should be unpacked and inspected, and the rest of the material should be checked regularly during installation.

Mechanical damage to the stone slabs is not allowed. Any form of repairing the damage or patching is not acceptable. Damage to the edges of the stone is also not acceptable.

Vertical displacement between two adjacent stone slabs after installation (lippage) is not allowed.

Cutting and finishing of stone slabs on site is allowed only on the borders of the surfaces where the stone is installed and where it is necessary due to penetration of installations or similar reasons.

Adhesives to be prepared and used strictly according to the manufacturer's instructions. The space between the stone slabs and the substrate must be completely filled by adhesive, no cavities are allowed.

The installation should be without joints.

The temperature in the room, during the installation, must not be less than 10°C. This temperature should be in the room also 7 days after the completion of the installation. After the work is finished, it is not allowed to move people in the room for a period of 3 days.

Upon completion of the laying of stone slabs on the walls and floors, stone surfaces shall be thoroughly cleaned in accordance with manufacturer's approved cleaning instructions and the contractor should check again the performed works, particularly whether the position of all installation outlets are done as per design.

In case of detection of minor damage to the installed slab it is allowed to repair the damage with repair mixtures tinted in the colour of the stone, with the approval of the supervisor. If the repair does not give satisfactory results, the damaged slabs must be replaced.

Before the start with grouting, the contractor has to prepare mock-up and invite the supervisor to approve the beginning of grouting in writing. Grout mass to be prepared and used strictly according to the manufacturer’s instructions.

Expansion joints should be done on every 40m2 of stone cladded surface, at the junction of floors and walls and without exceptions above the structural movement joints. The width of the expansion joint is at least 10 mm. Joints should be filled with a permanently elastic sealant on a polyurethane base.

Before applying the impregnation, the surface of the stone should be thoroughly cleaned. Impregnation should be applied according to the manufacturer's instructions, evenly, by hand (brush, roller, etc.) or by sprayer.

Stone surfaces should be protected from contact with acids, even those in alcoholic beverages and juices. Hot items should never be left on the surface of the stone. Stone surfaces should be cleaned in accordance with the maintenance instructions provided by the contractor.

4. Supervision and measurement of works

After the material is delivered to the site, the supervisor should check whether the material is delivered undamaged and whether it is in accordance with the approved sample.

Supervisor is obliged, before the beginning of the works, to check the condition of the rooms and approve the commencement of works. During the execution of the works, supervisor is obliged, on daily basis, to visually check the appearance of performed works. Verticality of the walls, horizontality of the floors to be checked by the mason's bubble level.

Inspection of areas receiving down washed lighting shall be done with the down washed lighting turned on.

The executed works to be calculated per sqm of cladded area. Areas not bigger than 0.5m2, that are not cladded by stone slabs, should not be subtracted from the total quantity.
Plinth is calculated per m1. Special pieces (treads, risers, windowsills, thresholds, tops, etc.) are calculated per piece. If the deviations in the dimensions of the installed elements are from the contracted up to 10%, this difference is not considered in the calculation.

March, 2021
Please note that the technical specifications on this web site are templates only, information provided should be carefully checked and aligned with your project needs.
Final surface applied to the face of stone slab during fabrication can be: polished (treated by polishing disk with grain size F.600 to F.2000), honed (surface finish having a dull polish or matt surface, treated by polishing disk with grain size F.120 to F.400), flamed (surface texture obtained by thermal treatment the stone using a high temperature flame), bush hammered finish (finish obtained by using a bush hammer), tooled (finish resulting from the mechanical surface treatment with tools), axed finish (rough and rugged surface achieved by using a punch or axe), pointed finish (semi-rough finish achieved by using a point chisel), sand blasted finish (a matt finishing resulting of impact of the sand or other abrasive grains expelled by a sand jet) etc.
According to the EN12004 adhesives are classified as follows:
C - cementitious
D - dispersion
R - reaction resin
1 - normal characteristic
2 - improved/additional characteristics
F - fast setting
T - reduced slip
E - extended open time
S1 - deformable
S2 - highly deformable
According to the EN 13888 grouts are classified as follows:
CG - cementitious grout
RG - reaction resin grout

1 - normal characteristic
2 - improved/additional characteristics
A - high abrasion resistance
W - reduced water absorption
Natural stones are classified as Class A1 by reaction to fire unless containing asphalt or organic patching, fillers or other similar products, at greater than 1% by mass or volume. In that case the stones shall be tested for reaction to fire and classified in accordance with EN 13501-1.
If the floor is to be covered with high gloss polished slabs, the best results are achieved when matt slabs are installed (e.g. treated by polishing disk with grain size F.300) and then the floor with already installed slabs is polished with diamond tools to a high gloss.