Arc Pro-Flex Slow Set Tile Adhesive

Arc Pro-Flex is a white, flexible, regular-setting, cement-based, highly polymer modified, thin-bed ceramic tile adhesive. It is suitable for fixing all types of ceramic floor and wall tiles, including mosaics, porcelain, fully vitrified tiles, marble, natural stone, slate etc. Arc Pro-Flex is ideally suited for application onto timber panels, plywood, concrete, block work and floor screeds without the need to include a flexible admixture in the mix. It has improved flexural strength, water-resistance and is suitable for swimming pools, underfloor heating applications and both interior & exterior use.

substrate preparation

The substrate must be structurally sound, dimensionally stable and strong enough to support the tiling installation and expected traffic. Surfaces to be tiled must be clean, suitably dry and free from contamination such as dust, paint, oils, grease, sealers or any other substance which may impair adhesion.
All tiling should be carried out to current best practice and relevant standards. For further information or details of substrates not covered below, consult Arc Tiling Guide.

Concrete: Concrete should be a minimum of 6 weeks old. Prime with Arc Tiler’s Primer diluted 3 parts primer to 1 part water.

Power-floated concrete: Mechanically abrade surface and vacuum dust. Prime surface with 1 coat Arc Tiler’s Primer Plus.

Sand Cement Screeds: New screeds should be a minimum of 4 weeks old. Prime with Arc Tiler’s Primer diluted 3 parts primer to 1 part water.

Gypsum screeds: Screed must be confirmed dry and the residual moisture content must be below 0.5%. Mechanically abrade surface and vacuum dust. Prime surface with Arc Tiler’s Primer diluted 3 parts primer to 1 part water followed by one neat coat of Arc Tiler’s Primer.

Timber floors: Timber substrates must be sufficiently rigid and supported to be free from excessive deflection under expected loads. Arc recommend overlaying timber floors with Arc MagnaBoards, screw fixed at 150mm centres. Where plywood is used as overlay it must be exterior grade and a minimum of 15mm thick. Prime boards with Arc Tiler’s Primer diluted 3 parts primer to 1 part water.

Blockwork / Render: New blockwork must be a min New Gypsum Plaster – Gypsum plaster must be at least 4 weeks old. Polished plaster must be brushed with a stiff brush. Weight of tiles and adhesive must be less than 20kg/m2. Prime with Arc Tiler’s Primer diluted 3 parts primer to 1 part water.

Plasterboard: For plasterboard without a skim finish, weight of tiles and adhesive must be less than 32kg/m2. Prime with Arc Tiler’s Primer diluted 3 parts primer to 1 part water.

Plywood Walls: Timber based boards including plywood are no longer recommended substrates for tiling. If they are present, Arc recommend replacing them or over-boarding them with Arc MagnaBoards.

Underfloor Heating: Piped underfloor heating systems must have been fully commissioned to maximum running temperature. Turn off heating 24hrs prior to tiling (or in cold conditions to below 15°C). When tiling is completed allow 7 days before switching on heating and increase the temperature gradually by max 5°C per day.

Movement Joints: Ensure there is adequate provision of movement in the tiling installation by the inclusion of sufficient and adequate joints. This is particularly important on heated screeds and with larger tiles.

Priming: Generally prime absorbent surfaces with Arc Tiler’s Primer diluted 3 parts primer to 1 part water and non-porous surfaces with 1 coat Arc Tiler’s Primer Plus. Allow primer to dry before tiling.


mix preparation

Do not use when temperatures are below 5°C. Pro-Flex should be added to water in a clean container whilst mechanically stirring and mixed thoroughly to give a soft, slump-free, easily worked mortar. The recommended mixing proportions by volume are 1 part water to 3 parts powder (approx 5L water per 20kg bag). The consistency of the paste can be adjusted with slight additions of water or powder at the initial mixing phase, however part-used adhesive should never be “freshened up” with later water additions.


For fixing ceramic tiles or mosaics, use a notched trowel to give a ribbed mortar bed on the substrate into which the tiles are firmly bedded with a twist and slide action to ensure full contact. Use a 3mm x 3mm notch at 6mm centres for mosaics and thin flat backed wall tiling, a 5mm x 5mm notch at 10mm centres for general wall tiling and 10mm x 10mm notch at 16mm centres for floor tiling. The position of the tiles can be adjusted up to 10 minutes after initial fixing. Open time of the exposed mortar bed is approximately 20-30 minutes, depending on surface porosity and site conditions. It is recommended that tiles with raised or studded back profiles, (or in situations where dampness is likely after tiling), should be buttered to ensure solid bed fixing. Do not trowel out an area of adhesive greater than can be tiled over within a 10-15 minutes period. Surfaces such as rutted concrete and masonry block-work which are rough and uneven may first be levelled with Arc Floor Levelling Compound. Adhesive should not exceed 6mm in depth. Back-butter large format tiles and natural stone tiles to achieve maximum bonding.


Grouting may proceed as soon as the tile bed is sufficiently firm, which for Pro-Flex will be after approximately 24 hours at room temperature. This period will be slowed by lower temperatures and accelerated by higher temperatures.



  • Porcelain, Ceramics, Terracotta, Quarry, Quartz, Glass, Marble, Mosaics, Limestone, Travertine, Natural Stone, Slate.


  • Plywood, Concrete, Plaster, Screeds, Backer Boards, Anhydrite Screed, Underfloor Heating, Plasterboard, Existing Tiles, Render, Brick & Block, Heated Screed, Vinyl Tiles, Fibre Cement, Asphalt Flooring.
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