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A general-purpose lime undercoat plaster. Suitable for most masonry backgrounds.

Great for renovation, conservation or eco-friendly new builds, Duro lime undercoat offers superior levels of breathability - perfect for walls with damp or salt problems since water can evaporate easily and does not remain trapped where it can damage stone, brickwork and wood.

Duro lime plaster base coat is also flexible and long-lasting, so it's more resilient to cracking or crazing compared with a site mixed lime render.

Duro is applied as a standard base coat plaster and finished with a finishing plaster such as Lime Green Solo or Fine stuff lime putty plaster.

For situations where extra a lightweight thermally insulating mix is required see our Ultra undercoat, which contains insulating beads.

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Ideal for old stone and brick walls

Use as a "scratch" coat

Highly breathable, durable and elastic.

Bring walls to a level and consistent surface before the final finish is applied

What is Duro for?
This product is a premixed lime undercoat for masonry. Just add water and used to build out the levels of the wall true and straight before applying a lime plaster finish coat, or to level the walls before applying Warmshell Woodfibre Boards.

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Weight: 25 kg
Coverage (per bag): 
Over 1m² each 1mm of thickness requires approximately 1.7kg
- at 10mm thick 1 bag will cover 1.5m²
- at 15mm thick 1 bag will cover 1m²
- at 20mm thick 1 bag will cover 0.25m²
Vapour Permeability: 5 to 15 µ
Compressive Strength: 1.5 to 5 N/mm²
Dried Density: 1600 to 1700 Kg/m³
Composition: Natural Hydraulic Lime, sands, calcium carbonate. Less than 1% admix for air entrainment and water retention

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Preparation

Remove dust, surface contamination, dirt or lichen and loose or friable existing coatings. Where necessary repair and consolidate masonry and structural defects beforehand. Painted or waterproof surfaces will need special treatment before applying Duro, seek further advice. Before application dampen masonry with clean water to control suction. For low-porosity brick or stone or difficult backgrounds a splatter-dash can be applied of Lime Green Natural Stipple For highly absorbent surface indoors the range of Lime Green Silic8 Primers are also suitable.

Mixing

Duro can be mixed in a drum mixer, a paddle mixer, or a suitable 3-phase mixer pump. Add the bag slowly to the mixer, carefully avoiding creating too much dust. Add approximately 4 ½ to 5 litres of water per bag. Mix for between 3 and 10 minutes. Duro may be re-tempered for up to 4 hours after being mixed.

Application

Use Duro in temperatures of 5°C and rising or 30°C and falling. Apply in coats of around 10 to 15mm, or thicker if dubbing out. Once ruled off and ready key the coat using a render comb in a regular wavy pattern if further coats of Duro are being applied. For the final undercoat before finishing, apply a light key using a devil float. Leave the Duro to set and harden for between 2 and 7 days depending on the temperature. Following coats should be applied while the Duro is still “green”.

Aftercare

Cover with hessian or mortar fleece and cure the coat by misting with water to control drying. Protect from drying winds, strong sun, frost and driving rain until hardened and dry.

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