Outline specification : plastering, rendering

Product Description

Unilit 25 is a traditional, dry premixed lightweight mineral mortar based on natural hydraulic lime as the binder and well-graded expanded aggregates.

Unilit 25 is characterised by a slow but strong bonding, a high plasticity, a low content of soluble salts and an excellent water vapour permeability.

The natural hydraulic lime mortar is inherently stable and designed to reduce problems of micro cracks along with premature drying out.

The natural hydraulic lime binder, used to prepare the preblend, conforms to the European Standard EN 459-1, NHL 5 for building limes. The mortar Unilit 25 conforms to the European Standard UNI EN 998-1.

Application Area

Unilit 25 is especially suited for the application to highly porous substrates, such as lightweight insulating blocks, silicate or gypsum blocks, cellular concrete, etc.  Irrespective of whether used internally or externally,

Unilit 25 will regulate the moisture content present within the walls enabling them to dry out in the utmost favourable conditions. All common moisture problems can be solved as such. The control of the moisture content within the substrate will prevent also the occurrence of mortar joint lines appearing in the render finish.

Unilit 25 can perfectly be applied in new construction, renovation as well as restauration, both internally and externally.


Prior to application, the substrate must be cleaned and freed of all traces of oil and grease. The substrate benefits from being slightly dampened. Saturation of the substrate is not recommended, as this will influence negatively impact upon the bond of the hydraulic lime mortar to the substrate as well as the aesthetic appearence.

The mortar is mixed with clean water at a ratio of 5 to 7 litres of water to a bag of 30 kg ready mixed natural hydraulic lime powder. Mixing is undertaken with a slow speed electric paddle for a period of 3 to 5 minutes. A creamy workable mortar is obtained, which has approximately 2 hours of open time.

The mortar is applied either manually or by mechanical means at the required thickness. A drying period of 1 to 2 days must be respected.

The lightweight mortar Unilit 25 may not come into contact with surfaces below ground level. Basements and other places susceptible to rising damp must be treated with the stabilising mortar Unilit 30. The use of stainless brick mesh is recommended where there is a likelihood of structural movement.

The mortars must not be applied at temperatures below +5°C nor when a risk of frost exists. They should never be applied on to a frozen surface or in the case of thick fog. In hot, windy and dry conditions measures should be taken to prevent accelerated drying out of the freshly applied mortars. Applied mortars must be protected from frost and direct sunlight for 48 to 72 hours after their application.

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