Roundtower NHL 3.5 Coarse is a factory-blended, dry ready-mixed lime mortar made with Natural Hydraulic Lime (NHL 3.5) and a 5mm down coarse kiln-dried sand. Designed for bedding, pointing, and general-purpose masonry, this mortar is also suitable for use as a base render coat, particularly in traditional or breathable construction.
Roundtower NHL 3.5 Coarse combines the strength and breathability of NHL 3.5 with selected additives that enhance workability, extend open time, and reduce shrinkage risk, all while maintaining the essential properties of a cement-free, vapour-open lime mortar.
Key Benefits
✅ Pre-Mixed for Consistency – 2:5 NHL to coarse sand ratio ensures reliability and performance across bags.
✅ NHL 3.5 Strength – Suitable for medium-strength applications, including external pointing and bedding.
✅ Improved Workability – Extended open and finishing times make it ideal for site work.
✅ No Cement or Synthetic Additives – Breathable and conservation-appropriate.
✅ Versatile Use – Suitable for new builds, historic masonry, and breathable render systems.
✅ Eco-Friendly Packaging – Supplied in recyclable 25 kg bags with polythene lining.
Applications
🔹 Pointing – For stone, brick, or block masonry in both restoration and new build settings.
🔹 Bedding Mortars – For laying block, brick, or natural stone.
🔹 Base Render Coats – Use as a undercoat in breathable lime plaster systems.
🔹 General Masonry Work – Ideal for wall construction where vapour permeability and moderate strength are needed.
🔹 Conservation Projects – Suitable for use where NHL 3.5 binder strength is compatible with the host material.
Technical Performance & Coverage
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Binder: Natural Hydraulic Lime (NHL 3.5)
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Mix Ratio: 2:5 (lime to coarse sand)
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Sand Size: Coarse (up to 5 mm)
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Compressive Strength: Moderate (based on NHL 3.5 binder)
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Coverage (Rendering): ~1.4 m² at 10 mm thickness per 25 kg bag
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Coverage (Pointing): ~25 bricks per 25 kg bag
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Yield: ~13.5 litres of mortar per 25 kg bag
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Open Time: Minimum 8 hours once mixed, longer in cooler conditions
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Packaging: 25 kg bags (40 bags per 1 tonne pallet)
Mixing Instructions
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Add 4–5 litres of clean water per 25 kg bag, adjusting for desired consistency.
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Start by adding 60–70% of the water to the mixer, then the dry mortar.
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Mix for 5–10 minutes until fully blended.
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Let the mortar quench (rest) for 10–20 minutes, then remix briefly before use.
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If needed, a small amount of additional water may be added to maintain workability.
Why Choose Roundtower NHL 3.5 Coarse ?
Roundtower NHL 3.5 Coarse is the ideal choice for medium-strength lime mortars where consistency, ease of use, and breathability are key. From stone bedding to base coat renders, it delivers the strength and vapour permeability required for heritage restoration, traditional wall construction, and natural building systems—all without the risks associated with cement-based mortars.
