The key to success when installing ARDEX products is to achieve a good bond between the substrate and the underlayment or topping and also the flooring adhesives (this includes membranes and tile adhesives as well). Proper preparation of the surface is the most important factor in achieving this bond. Whatever topping or underlayment is used to level, smooth, or repair a substrate’s surface, it will only be as strong as the surface to which it is bonded. The same applies to other materials applied to the surface such as flooring adhesives, membranes or tile adhesives. The surface, therefore, must be sound, clean and free of oil, grease, wax, dirt, asphalt, curing compounds, latex and gypsum compounds, dust, paint or any contaminant which might act as a bond breaker.

The methods required to properly prepare the subfloor vary with the type of substrate, its surface and condition. Several methods of preparing a substrate may be available, and some methods are used because they are cheaper, easier or faster, depending upon the size of the job. However, taking shortcuts in proper substrate preparation can be an invitation to installation problems and failures. This Article is by no means an all-inclusive guide but is intended to give recommendations for many common substrate conditions and the proper preparation.

Surface preparation for flooring materials to be installed:

Information to be provided by flooring contractor

– Whether any repairs to the subfloor are required,
– Whether the surface of timber subfloors needs to be sanded.
– Whether the surface of the subfloor requires cleaning to remove existing floor covering, any deleterious materials such as grease, oil, paint curing or parting agents, or any surface treatment which could adversely affect adhesion.

Surface preparation

Before laying operations begin, materials such as grease, oil, paint, existing floor coverings and their adhesives, curing or parting agents, or any surface treatment, particularly oxides, mark-out paints, wax crayons which could adversely affect adhesion, discolouration or any other detrimental effect shall be removed from the subfloor via mechanical means.

New concrete subfloors surface

New concrete subfloors on which floor preparation materials and the resilient covering are to be laid without underlay, shall be finished to a smooth and porous surface. Burnished concrete surfaces, waterproofing additives, curing compounds and other types of treatments or coatings will adversely affect the adhesion of the floor preparation and resilient covering to subfloor and shall be removed by mechanical treatment methods. Concrete surface physical defects which also compromise adhesion of flooring systems, such as laitance or rain damage to the concrete surface, shall also be removed by mechanical preparation methods. All loose materials or dust present either as building debris or residue from mechanical preparation shall be removed by vacuum cleaning. Surface cosmetic defects such as score marks, grooves or depressions shall also be removed either by mechanical preparation methods or the installation of an underlayment.

CONCRETE

Concrete floors must be solid and sound. Over-watered, frozen, rain damaged or otherwise weak concrete must be removed mechanically to provide a sound base. In addition, concrete should be evaluated for moisture and be free of oil, grease, wax, dirt, asphalt, curing compounds, latex and gypsum compounds, dust, paint or any contaminant which might act as a bond breaker.

New Concrete:
There are two important reasons to avoid the installation of ARDEX products over concrete, which is less than 28 days old:
1) Drying and shrinkage cracks may occur as the concrete cures. Installing flooring ARDEX products over “green“ concrete will result in the cracks telegraphing through the ARDEX underlayment as they develop in the concrete. To avoid this, allow the concrete to cure a minimum of 28 days and repair any cracks before proceeding with the installation of the ARDEX material. NOTE: Some selected tile adhesives can be applied after seven days.

2) ARDEX primers must be installed over a completely dry surface to assure proper bonding. Under many conditions, concrete may not be free of excess moisture before 28 days. Caution: ARDEX primers, underlayments, toppings and adhesives are not vapour barriers and will allow free passage of moisture.

Power-Floated concrete/Hi-strength concrete greater than 35 MPa. Burnished concrete finishes, Hi-strength concrete greater than 35 MPa including post-tensioned, suspended concrete, off-form concrete etc, represent a finish that is extremely dense (non-porous) and with no surface profile. Adhesion to these concrete finishes without mechanical preparation is questionable. It is recommended to remove the glazed/dense surface finish to provide a roughened open porous matrix of the concrete.

Forced Drying. If forced drying of the concrete slab is used, care must be taken that no oils are present in the air source as these can contaminate the drying surface. Also, if entire rooms are heated by salamanders or other heaters using fossil fuels, the exhaust must be vented. This will prevent carbon dioxide from combining with calcium hydroxide in fresh concrete which can form a weak layer of calcium carbonate on the surface by a process known as carbonation. If carbonation does occur, the floor must be mechanically re-prepared.

Curing Compounds. The vast majority of curing compounds are bond breakers, which will inhibit the ability of an underlayment or topping, flooring adhesive, membrane or tile adhesive to bond to the concrete substrate. They can also affect the drying curing times. Regardless of the type of curing compound used, including dissipating curing compounds, these materials must be completely removed prior to proceeding with the installation of the flooring system.

Acrylic Sealers. Acrylic sealers can oxidize and flake off from exposure to ultraviolet light and air. Although acrylic sealers may not contain bond-breaking oils, waxes, resins or rubbers, a good bond cannot be guaranteed and complete removal is required.

Laitance, Weak Surface Areas, Frozen, Frost-Damaged or Overworked Concrete. These surfaces are unsuitable for flooring systems and any signs of spalling, scaling, delamination, crumbling or laitance must be removed down to solid, clean concrete. A hammer or heavy instrument should be used to sound out weak, hollow and unsound material. The concrete surface has a layer of laitance which needs to be removed back to the sound material underneath.

Contaminated Concrete. All oil, grease, wax, dirt, chemicals, asphalt, latex and gypsum compounds, dust, paint, or any contaminant which might act as a bond breaker must be completely removed before installing a flooring system. Failure to remove these contaminants is the most common cause of flooring materials de-bonding from the sub-surface. Chemical methods may be successful at removing oil if it has not penetrated too deeply, however, the material used to remove the oil or grease may itself leave a contaminant behind. To remove any doubt, the substrate should be mechanically cleaned down to sound, solid, uncontaminated concrete.

Asphalt and Tar-Based Residues. Although quite different in composition, both asphalt and coal tar-based residues on concrete substrates pose their own threats to the performance of flooring system. Roofing asphalt is often found on concrete roof decks upon which new floors are to be built. Tar products can also be found as a contaminant in these roof type renovation projects, as well as in the adhesive used on old wood block floors in warehouses and factories. All asphalt and coal tar-based materials found on concrete substrates must be completely removed by mechanical means down to clean, sound, solid concrete prior to the installation of any flooring system. Arditex NA may be used in some situations for advice, please call your local ARDEX Representative.

Old Adhesive residues

This is a common source of surface contamination and it is necessary to remove them entirely from the substrate before a flooring system is installed. This can easily be achieved by mechanical means. It is not uncommon for an installer to be encouraged to apply toppings over old adhesives. To provide a primer or system to adequately bond to most of these compounds isn’t the problem, but you are then relying on the standard of the previous preparation, the bond strength of the old adhesive and of course the cohesive strength, in itself, of the adhesive or coating. The risk of the old adhesive (coating) lifting from the substrate or indeed splitting within itself can sometimes be very high depending on the type of floor covering, the environment and usage. Certain products can have a high surface tension, putting enormous pressure on the old adhesive such as parquetry. Some adhesives, such as the old bituminous types (Black Jack) may be reactivated by the new adhesive and in time cause underlayment and subsequent floor covering to de-bond. ARDEX Arditex NA can be applied over old residues if there is no option to remove the contaminants however, this application is entirely dependent on the condition of the bond of the old adhesive, and the quality of the workmanship for advice, please call your local ARDEX Representative. A minimum of 3mm of Arditex must be applied to minimise the risk of any new adhesives re-activating the old residues with the risk of the whole surface debonding.

Rain damaged concrete. Concrete which has been affected by rain prior to cure must be mechanically prepared back to the sound underlying material. The rain damage concrete is mechanically very weak and can de-bond under traffic loadings, and may be weak enough to fail when tensile strain from the drying topping is applied.

Definitions of Mechanical means ‘Mechanical means’ is the process of surface preparation performed by application of applied physical forces to the substrate surfaces to remove contamination. For the purposes of installations on concrete, this refers to the use of diamond grinders, scarifiers and captive shot blasters. , or smaller areas this can include chippers and nail gun type scabblers. When installations are to be performed on timber floors ‘mechanical means’ refers to floor sanders.

ARDEX Preparation