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 NHL2 Promix Medium or 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 costs.

The superior performance of Cornerstone Insulating render means 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 that enables it to adhere to virtually any surface. 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, as it meets the requirements for improving the thermal performance of a wall whilst maintaining a permeable fabric. 

Preparation

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

Mixing

Cornerstone Insulating Render is a dry-mix product that only requires the addition of water. 1 bag will usually require 4 to 5 litres of clean potable water. However, the water addition will vary depending on the application and the 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 water to the mortar, and that, provided 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 of 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's consistency will improve, making it easier to work with. 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.

Coverage

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

Storage

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

Downloads

• Cornerstone Insulating Render Data Sheet
• Cornerstone Insulating Render Safety Data Sheet
• Insulating Render and Part L1B - Building regs
• Insulating Render and Part C - Building regs
• Thermal Conductivity Calculations
• Mixing And Application Guidance

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