Contact Us

  • Celtic Sustainables
  • 01239 777009
  • 9 Parc Teifi Cardigan Ceredigion SA43 1EW


About us

Put something nice about your company here...

Skip to main content
Free delivery icon
Free delivery icon
Free delivery icon

Cornerstone Insulating Render - 9kg

Cornish Lime


Prices Include VAT


Prices Include VAT

Adding to cart… The item has been added

Cornerstone Insulating Render is a dry mixed render/plaster designed to reduce heat loss in buildings constructed with solid walls. Suitable for both internal and external applications it is applied as a base coat and then finished with a Lime finishing plaster. We recommend Cornerstone CLM66 for internal finishing and Cornerstone Drymix NHL2 fine as an external finish. 

The render is lightweight and can be applied in multiple coats. Each coat can be applied at a thickness of 30mm helping to reduce labour times and cost.

The superior performance of Cornerstone Insulating render means that it is 50% more insulating than the closest performing market alternative and is priced to meet or cost less.

Cornerstone insulating render contains NHL2, recycled aggregates and an additive which enables it to stick to virtually any background. There are no organic aggregates in the plaster which could be affected by moisture. The mortar also has fibre additions to improve the flexural strength of the render, distributing stresses across the render helps reduce point loading, and negates the need for any mesh to be applied to the wall or inserted within the render.

Insulating render also 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. 


As with any lime plaster application, ensure surface is clean, free of dust and loose particles. For porous substrates, damp down to ensure good adhesion and to prevent rapid drying which can compromise the durability of lime plasters. 


Cornerstone Insulating Render is a drymix product, only requiring the addition of water. 1 bag will usually require 4 to 5 litres of clean potable water. However the water addition will vary according to the application and desired consistency/workability of the mortar. Avoid adding too much water to start as a mix that is too wet will result in shrinkage, especially when used as a render.

Note: It is possible that some settlement or separation of the dry ingredients may occur during transit; when mixing part bags, it is especially important that the dry contents are thoroughly blended prior to mixing with water.

For drum type mixers, it is essential not to overfill the mixer.

We accept that it is often site practice to add the water to the mortar, and providing the mortar is well mixed and not too wet, this method will be sufficient.

Mix the contents of the bag with 60-70% of the required amount water. Keep mixing until the water is thoroughly distributed, then add additional water to achieve your desired consistency. Mix for a minimum of 5 minutes.

Quenching - Like traditional lime mortars, Cornerstone Insulating Render will benefit from Quenching; after mixing, allow the mortar to stand for 10 to 20 minutes before use. During this rest period the mortar consistency will improve making it easier to work. If after quenching the mortar still requires extra water, add it slowly and ensure it is fully mixed in.

Once water has been added, Cornerstone Insulating Render has an open time of at least 18 hours.


After mixing, a bag will produce approximately 13.8 litres of mortar.

For every 10mm of render thickness, you would need 0.72 bags per square meter. (1.38 m2 per bag).
e.g. to calculate 10m2 at a thickness of 50mm
multiply 0.72 (the consumption per 10mm) x 10 (total area) x 5 (multiple of 10mm to get the required 50mm thickness) = 36 bags


Store in dry conditions, in unopened bags and keep clear from the ground. Protect bags from water and damp. - Use within 6 months of manufacturing date (printed on bag).


Cornerstone Insulating Render Data Sheet

Insulating Render and Part L1B - Building regs

Insulating Render and Part C - Building regs

Thermal Conductivity Calculations