PRO-511 Hardset is a high-elasticity, fibre-reinforced internal undercoat designed to level and prepare masonry surfaces before the application of finishing plaster. Formulated with white Portland cement, reinforcing fibres, polymers, modifying additives and mineral fillers, it creates a strong, stable base while offering excellent flexibility and crack resistance. It is ideal for flattening uneven brick and blockwork backgrounds, helping create a more consistent surface ready for final plaster and decorative finishes.

Why Choose PRO-511 Hardset?

• Designed to level and prepare internal masonry surfaces before finishing plaster.
• High-elasticity, fibre-reinforced formulation for added flexibility and crack resistance.
• Helps create a strong, stable base for internal plaster systems.
• Ideal for flattening uneven brick and blockwork substrates.
• Suitable for brick, blockwork, existing cement plasters, lime plasters and renders that need surface correction.
• Leaves a surface ready to be keyed for subsequent internal plaster finishes.
• Offers an A1 reaction to fire classification.

Intended Uses

PRO-511 Hardset is designed for internal levelling and preparation of masonry substrates before finishing plaster is applied. It is suitable for use on brick, blockwork, existing cement plasters, lime plasters and renders where flattening or surface correction is needed. It is particularly useful when uneven backgrounds need to be trued up before plastering, helping create a more uniform and reliable surface for the next stage of the build-up.

Substrate Preparation

Backgrounds should be clean, sound and free from dust, grease, paint residues, mortar droppings and other contaminants before application. The data sheet states that the product must be applied to a stable substrate that has been correctly primed using PRO-313 Green Internal Grit. Proper preparation helps support good adhesion and a more consistent finish.

Product Preparation

PRO-511 Hardset should be mixed with approximately 6.5 litres of clean, cool water until a homogeneous, lump-free consistency is achieved. After mixing, the material should be left to stand for 5 minutes before being remixed thoroughly. For consistency across the job, all batches should be prepared in the same way. Material that has started to set should not be re-mixed.

Application

Apply PRO-511 Hardset to the prepared substrate using a hawk and trowel to a thickness of 3–20mm. Once applied, the surface should be levelled and straightened with a straightedge, with high spots removed as needed. The surface is then finished with a devil float to create a key ready for the internal plaster.

Application Conditions

Application should be carried out when ambient, substrate and material temperatures are between 5°C and 25°C. During application and drying, the material should be protected from rapid drying and unsuitable site conditions that may affect curing.

Technical Data