Roundtower Insulating Plaster

Roundtower Insulating Plaster

Lightweight plaster which offers low strength, high flexibility, high vapour permeability and advanced thermal performance, for use on solid walled masonry.

This product is not available to buy online. Please contact us for pricing and more information.

€ 19.56 EUR
Every effort has been made to ensure the accuracy of our digital colours and textures however due to limitations with technology, we strongly advise purchasing sample products for testing in situ prior to the full order being placed.
All prices specified on our website include VAT. Contact our team for bulk pricing and trade discounts.
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Delivery Information

Unless otherwise specified all products within Ireland should be delivered within 2-3 working days. Please contact us for delivery options outside of Ireland or if you wish to ship to Northern Ireland.

Our stock is primarily shipped by Fastway or via the pallet network depending on the total weight of the order. The delivery method will be automatically assigned and priced at checkout. All delivery prices include VAT.

Main Purpose

Roundtower Insulating Plaster has been specifically designed to reduce heat loss in solid walls and older buildings.


Approximately 1.7m2 at 10mm thickness.

Plaster, Insulation and Dehumidifier all in one. Roundtower Insulating Plaster is a lightweight plaster which offers low strength, high flexibility, high vapour permeability and advanced thermal performance, for use on solid walled masonry.

Insulating Plaster has been specifically designed to reduce heat loss in solid walls and older buildings. Working as a lightweight base coat for rendering and plastering applications, Insulating Plaster offers significantly improved insulation and moisture management, as well as much faster application times compared to conventional lime renders.

Key Benefits

  • Work Quicker, Apply Thicker – Insulating Plaster can be applied up to 30mm depth as a single coat, compared to standard lime mortar which is 10/12mm per coat, significantly reducing labour times and costs.
  • Let Your Walls Breathe – behaves the same as a standard NHL2 render, offering a highly vapour permeable and highly flexible coating, helping reduce issues such as damp and decay
  • Highly Insulating – with a measured K Value of 0.12, a 25mm coat will improve the U Value of a solid wall by around 40%, whereas a 50mm coat will improve the U Value by around 60%.
  • A Dehumidifier for Your Walls – by incorporating non-porous aggregate Insulating Plaster helps to regulate moisture movement through the wall and reduce cold spots. Independent testing verifies how Insulating Plaster can absorb, store and buffer excess moisture, releasing it when suitable and never trapping it within the wall, improving the air quality and comfort of internal spaces.
  • Space Is A Premium – Insulating Plaster can be applied directly the wall it does not require framing or boards which can reduce space. If you are looking to maximise insulation it can also be incorporated within a boarded system.
  • Natural Mineral Ingredients – made using only NHL2, recycled aggregates and additives enabling it to be used on virtually any background and contains no organic content so no fear of the coating rotting or breaking down.

Roundtower Insulating Plaster is designed to improve the thermal performance of solid walled masonry, whilst maintaining the high vapour permeability and low strength of an NHL 2 render. Insulating Plaster offers a viable solution for Part L1B legislation in that it meets the requirements for improving the thermal performance of a wall, whilst maintaining a permeable fabric which absorbs and readily allows for the evaporation of moisture and will not prejudice the character of the host building or increase the risk of long-term deterioration of the building fabric or fittings. With a measured K Value of 0.12, Insulating Plaster significantly outperforms similar systems both in terms of performance and cost. A 50mm application will improve the U value of a solid wall by 50% or more, significantly reducing heat loss.

Most available lightweight/insulating materials use aggregates that have a two-dimensional structure, when these are subject to pressure during application the aggregate can breakdown, reducing both the thermal performance and durability of the mortar. Roundtower Insulating Plaster uses a specialist recycled ultra-lightweight hardened aggregate with a three-dimensional structure, which does not breakdown under application and improves both the durability and insulating properties of the render.

Fibre additions improve the flexural strength of the plaster, distributing stresses across the render to help reduce point loading, and negate the need for any mesh to be applied to the wall or inserted within the plaster.

Insulating Plaster can also be used in sustainable construction projects as a basecoat onto natural building materials such as hemp, straw and rammed earth. The insulating properties help reduce the thermal expansion differentials between the background and any subsequent coatings.


For internal applications it can be applied as backing coat or through to finish coat, or finished with a lime plaster. For external applications, apply as a backing coat with Roundtower NHL2 Drymix as a finish.

Suitable for application onto most host surfaces. If working on weak/friable backgrounds such as cob, please contact us for further application information.

Please read the Roundtower Insulating Plaster DataSheet for full application information.

Each project is unique, always seek professional advice before undertaking a project.