Sustainable mortar solutions from SMET

The advantages of using NHL-based mortars over cement-based mortars are apparent from decades of experience and research. The manufacture of limes or NHLs consumes less energy and produces less greenhouse gases than that of Portland cement per unit weight.* 

Lime-based mortars also offer a range of advantages from a design perspective. 

Walls have improved ‘breathability’ to water and water vapour, which reduces the likelihood of frost failure of the unit materials and improves the internal living environment. 

Walls built with lime-based mortars have more tolerance to movement caused by thermal and moisture action, while movement within masonry walls built with lime-based mortars can be accommodated in the individual bed joints between the masonry units, reducing the need for vertical movement joints.

Finally, lime-based mortars are capable of self-healing microscopic cracks by plastic flow and diffusion and are less susceptible to sulphate attack, providing all-round consistently high-quality results. 

The SMET Professional range of quality lime-based materials is backed up with the expertise of a technical advisor. SMET is site focused, providing customers with industry specialists who will provide training, demonstration, and support in their application. 

The range includes pre-mixed EN 998-1 compliant renders and plasters for traditional hand or modern machine application, and EN 459-1 compliant SMET NHL 2, SMET NHL 3.5 and SMET NHL 5 natural hydraulic lime binders for conservation, repair, and sustainable new builds.

Why use Lime-based render and plaster?

SMET’s bauprocalc products are CE-marked, factory-produced hydraulic hardening skim coat plasters and render based on lime, specially designed for hand and machine application produced to DIN EN 998-1. Bauprocalc KG and bauprocalc 830 contribute to a healthy internal atmosphere. 

They are an excellent alternative to plaster and renders containing gypsum or patent cement that have less vapour- permeable qualities. They are ideal for kitchens, bathrooms and other rooms where high humidity levels are expected. Bauprocalc KG produces a mortar that is softer than cement mortar. After the initial set, stability and strength gradually build up over time, allowing enough flexibility to cope with minor settlement or movement in the building during this period, thereby reducing the risk of cracking. Bauprocalc 830 has unique properties, making it suitable for application on low, medium and high-density substrates, especially suited for the renovation of old/listed buildings and ecological new builds. Good vapour permeability performance allows an unhindered transference of excess internal moisture through the building to the outside, thereby contributing significantly to a balanced and healthy internal atmosphere.


SMET is delighted to have supplied its bauprocalc plaster and render for the lime rendering and plastering of Wilton House, helping Poplar Investments Ltd & Kelly Bros transform the 19th-century Belfast city centre building into unique, hotel-like, serviced apartments.

Michael Brannigan from Poplar Investments said, “Historical features are preserved not only in the appearance of the building but also in the actual build-up, which was exemplified by the use of lime plaster as it was done 200 years ago to ensure wall breathability” (Source: NB 32-4).

*Source: based on De Vekey, 2005.