Duro application overview
Surface Preparation
Before application of Duro any loose and friable materials must be removed, usually by brushing the surface. Brick & stone backgrounds are porous allowing the lime to be drawn helping it bond. The brick should therefore not be waterproofed or painted, so do not apply PVA. However, the suction will need to be reduced so the Duro does not dry rapidly. Dampening the surface with an even spray of clean water is sufficient to reduce excess suction from the background. This is usually repeated several times, so the bricks are damp but not saturated.
Mixing/Water Addition
Mixing Duro correctly allows for good workability. Time is required for water to spread completely into the dry powder. If the process is rushed then there may be insufficient water in the mix leading to rapid drying. Each 25kg sack of Duro needs mixing with 4-5 litres of clean water and for up to 10 minutes in a mixer. If a mechanical whisk is used then whisk for 2-3 minutes, then stand for 10 minutes before mixing again just before using it.
Application
Duro is applied in one coat of 15mm on straight walls in unexposed locations or applied in two coats up to 20mm for uneven walls or exposed locations. Using fibre mesh reinforcement is standard practice at corners of openings, or at junctions of dissimilar materials, the mesh can be doubled up at corners and around openings, in some cases the whole surface is meshed. Fibre mesh is embedded by applying the first basecoat in 2 passes with the mesh trowelled onto the first pass. The fibre mesh overlaps should be no less than 100mm. The mesh can be doubled up at corners and around openings./p>
DEach coat of Duro must be scratched to give a good mechanical key before further coats are applied. Always dampen down the surface prior to further coats. A second coat of Duro can be applied when the previous has adequately cured, usually after 2-4 days. Ensure the second is thinner than the first. The final coat of Duro must be keyed. The most effective method is with a nail or devil float when the surface has stiffened.
Curing
Duro should dry slowly and rapid drying needs to be prevented. In warmer weather water can be added to slow drying by lightly spraying the surface.
Additional protection such as a sheeted scaffold is used to protect from adverse conditions such as frost, rain, etc.
Adequate curing of a final external finish coat should be more stringent, ideally using a fully sheeted scaffold when outside.
Finish Coat
Outside Duro is finished with Lime Green Natural Finish applied at 5mm. This is available in a range of colours. As the surface begins to stiffen the surface is finished with a sponge float which reveals some of the aggregate on the surface.
Inside plaster usually has a smoother finish by applying Lime Green Solo plaster. Although the Solo plaster can be left undecorated it is usually finished with a breathable Lime Paint, or Beeck Mineral Paint.
View detailed Duro Guide
