Lime render
A selection of 9 natural hydraulic lime (NHL 5) rendering mortars: Unilit 15 (bond coat), 20 (VOLCALITE thermal insulation), 25 (lightweight base coat), 30 (damp remediation), 35N-M (pointing/base coat), 35F (fine pointing), 40 (water-repellent finish), 45 (finish), 65 (repair). Suitable for restoration and new build, with high water vapour permeability.
What is lime render?
Unilit lime render is a finishing or base-coat mortar made of pure natural hydraulic lime (NHL 5) and selected aggregates. The lime acts as the mineral binder: it sets slowly, then hardens on contact with the air, and gives a render that is compatible with old and new substrates alike.
The mortar is workable during application and hardens gradually, while keeping a high water vapour permeability (μ ≈ 4 to 12 depending on the product). Each Unilit variant meets a specific need: bond on a weak substrate (15), light thermal insulation (20 VOLCALITE), lightweight base coat on porous brick (25), treatment of a damp wall (30), standard or fine pointing (35N-M, 35F), standard or water-repellent finish (45, 40) and multi-purpose repair (65).
This range makes it possible to choose the mortar according to the hardness and porosity of the substrate, inside and outside, in new build and in restoration. The LIMETICS ETA (2018) covers exterior application on wood fibre and other insulating substrates.
Unilit is distributed in Belgium by Arte Constructo, in Schelle, a specialist in lime-based products for restoration and bio-ecological construction, which advises specifiers at design stage and on site.
Installation & uses
The render is prepared by slow mixing (3 to 4 minutes, at low speed), with a water-to-mortar ratio of around 0.18 to 0.25 L/kg depending on the product (0.16 L/kg for the Unilit 45 finish). The mortar remains workable for around two hours.
It is applied in two coats, wet-on-wet, to a total thickness of 3 to 4 mm for the finish (Unilit 45), and thicker for base-coat mortars. The finish is floated, sponged, trowelled smooth or polished, depending on the look required.
The minimum application temperature is +5 °C. The render is protected from frost and direct sun for 48 to 72 hours. No dehumidifier or hot-air blower is used while it sets, as it would draw the water out of the mortar too quickly.
The render can take a lime or silicate mineral finishing paint. The bags keep for 6 months in their original packaging, in a dry place.
About the producer
Arte Constructo is a Belgian supplier of lime-based products, based in Schelle, near Antwerp. The company distributes several ranges for restoration and bio-ecological construction: Unilit natural hydraulic lime mortars and renders, Coridecor decorative lime finishes and KEIM mineral silicate paints.
Drawing on long experience in restoration, it supports specifiers with technical advice at design stage and on site, and works with manufacturers of bricks and bio-ecological insulation.
Technical performance
Binder: NHL 5 lime to EN 459-1. Rendering mortar: EN 998-1. Strength: EN 1015-11 (compressive) and EN 1015-12 (bond). Density EN 1015-10. Grading EN 1015-1. Reaction to fire EN 13501-1. ETA LIMETICS (2018) for exterior application on wood fibre and other substrates.
Life cycle
Unilit mortars combine NHL 5 natural hydraulic lime with natural aggregates. Unilit 20 adds perlite and expanded sand for thermal insulation, and Unilit 40 a water repellent for the finish.
The Unilit range is distributed in Belgium by Arte Constructo, in Schelle, as pre-mixed mortars supplied in 13 to 30 kg paper bags. On site, the mortar is mixed with water and applied in coats whose thickness depends on the product.
No take-back scheme and no end-of-life scenario are documented for the Unilit range, which has no EPD. The renders are mineral lime mortars, rated A1 for reaction to fire.
FAQ
Which Unilit product suits which substrate?
Unilit 15 for bond on a weak substrate, 25 as a lightweight base coat on porous brick, calcium silicate or aerated concrete, and 30 to treat a damp wall. 35N-M and 35F are for pointing, 45 and the water-repellent 40 for the finish, and 65 for repair. Unilit 20 VOLCALITE, made with perlite and expanded sand, provides light thermal insulation.
Can wood fibre insulation be rendered on the outside?
Yes: the LIMETICS ETA, in force since 2018, covers exterior application on wood fibre and other substrates. The range remains very open to water vapour, with a μ of around 4 to 12 depending on the product.
How thick can each coat be?
It depends on the product: 20 mm for Unilit 20, 25, 30, 35N and 65N, 15 mm for 35F, 10 mm for 35M and 65M, and 5 mm for 65F, Unilit 65 coming in three gradings. Unilit 15 is applied at 2 to 4 mm as a thin render (P1) or 5 to 8 mm as a base coat (P2). The Unilit 45 finish is applied in two coats, wet-on-wet, at 3 to 4 mm in total, for 3 to 5 kg/m².
What conditions apply while the render sets?
The minimum application temperature is +5 °C, and the render is protected from frost and direct sun for 48 to 72 hours. Dehumidifiers and hot-air blowers must not be used, as they would draw the water out of the mortar too quickly.
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