ARDEX A125 Fine Coat Smoothing and Finishing Render Grey 22kg

ARDEX A 125 is ideal for leveling and smoothing surface irregularities on vertical and overhead substrates, including concrete, brickwork, blockwork, and previously applied cement/sand renders. It dries to a smooth, durable surface that can be left exposed or painted with cement-resistant decorative coatings. Suitable for both internal and external applications, ARDEX A 125 is particularly effective in moisture-prone areas, such as swimming pool halls and underground tunnels. Note: It is not recommended for use on low-strength backgrounds, such as lime/sand renders.

Surface Preparation

The surface must be rigid, clean, and free from dust, grease, and any other materials that could hinder adhesion, and it can be either dry or damp. It is advisable to use ARDEX Degreaser to remove oils, waxes, curing agents, and other contaminants from the substrate. Any loose surface coatings that are not firmly bonded should be removed before application. In-situ concrete, brickwork, and concrete blockwork should be a minimum of six weeks old to allow for initial drying shrinkage. Thoroughly remove paint, gypsum plaster, and other barriers to expose a clean, solid background. Settlement cracks can be filled with rendering mortar, but cracks caused by structural movement cannot be guaranteed to be eliminated. Small cracks should be enlarged for better contact with the material. Metal components require proper corrosion protection. When rendering over dense surfaces like old glazed bricks, ceramic tiles, or timber-framed constructions, or where old paint finishes cannot be removed, install anchored reinforcement securely fixed to the background, following the guidelines in BS 5385: Part 2. Proper substrate preparation is essential for ensuring the render adheres effectively. We recommend applying ARDEX AM 100 Rapid Hardening One Coat Render through the reinforcement, which can be applied up to 20mm thick, allowed to harden for at least two hours, and then smoothed with a thin layer of ARDEX A 125 for the desired finish.

Mixing

To mix ARDEX A 125, add the powder to water in a clean container while stirring, ensuring a thorough mix to achieve a slump-free, easily workable mortar. Using an ARDEX mixing paddle with a 10mm chuck variable speed electric drill is recommended for ease of mixing. The mixing ratio by volume is approximately 3 to 3½ parts ARDEX A 125 powder to 1 part water. A 22kg bag of ARDEX A 125 requires around 5½ to 6 liters of water. The pot life of the mixed mortar is approximately 4 hours at 20°C.

Application

Apply the mixed mortar with a suitable trowel to the prepared substrate as a bonding layer or scratch coat, approximately 1mm thick, then apply the ARDEX A 125 mixed mortar to the desired thickness, using the fresh-in-fresh method to reduce bubbling. The maximum application thickness is 5mm. For a smooth finish, lightly trowel the surface with a wet tool once it becomes firm. After drying for about 24 hours at 20°C, ARDEX A 125 can be painted or covered with other cement-resistant decorative coatings. For localized thicker applications, such as filling cracks and holes, use ARDEX A 46 Multi-Purpose Repair Mortar. For smoother finishes, apply ARDEX A 125 on top of ARDEX A 46 once it has set sufficiently, which can take as little as one hour at 20°C. For deeper applications over larger areas, ARDEX AM 100 Rapid Hardening One Coat Render can be applied from 2mm to 20mm, then smoothed with ARDEX A 125 in as little as 2 hours. For more details, consult the relevant datasheets or contact ARDEX Technical Services.