At Roundtower Lime, we specialise in high-performance insulating plasters that provide exceptional thermal insulation, vapour permeability, and moisture buffering, making them ideal for solid masonry walls in both heritage and sustainable modern buildings.
Our range of natural insulating plasters includes:
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Roundtower SuperTherm – An ultra-lightweight, vapour-open insulating lime plaster with a market-leading thermal conductivity of 0.0395 W/m·K, applied in layers up to 50mm in a single coat. Suitable for internal and external applications where maximum breathability and moisture control are critical.
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Roundtower Insulating Plaster – A cost-effective NHL2-based insulating render with integral fibres and a K-value of ≤0.12 W/m·K, suitable for leveling uneven surfaces and as part of internal and external insulation systems.
These breathable lime-based plasters are ideal for use in historic renovations, damp solid wall retrofits, and eco-conscious new builds. They provide a seamless finish while maintaining the natural hygrothermal performance of masonry substrates.
Whether you are looking to improve thermal efficiency, address condensation risk, or comply with conservation requirements, our insulating plasters offer durable, sustainable solutions tailored to traditional construction.
Frequently Asked Questions (FAQs)
Q1: What makes insulating lime plasters different from other insulation materials?
Lime insulating plasters are breathable, vapour-permeable materials that allow moisture to evaporate naturally. Unlike synthetic insulation boards, they help regulate indoor humidity and are ideal for use on solid walls where damp is a concern.
Q2: Can insulating plasters be applied to all masonry surfaces?
Yes, they are compatible with most types of brick, stone, block, and even uneven historic masonry. Surfaces should be stable and free from cement-based contaminants. A bonding coat or key coat may be recommended in some cases.
Q3: How thick should the insulating plaster be applied?
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Roundtower SuperTherm can be applied in 50mm coats, with a total thickness of 80mm+ where needed.
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Roundtower Insulating Plaster can be applied in 30mm coats and is typically applied between 30mm and 60mm.
Always follow manufacturer guidelines for maximum thermal performance.
Q4: Can I apply a finish coat directly over insulating plaster?
Yes. We recommend finishing with breathable lime topcoats such as:
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Roundtower Heritage Lime Skim (for internal use)
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Roundtower NHL 2 Coarse or Roundtower NHL 2 Fine (for external use)
All finishes should match the breathability of the base layers.
Q5: Is it suitable for conservation or protected structures?
Absolutely. Our lime-based insulating plasters are frequently specified for use in protected buildings due to their reversibility, non-destructive moisture management, and chemical-free formulation.
