Description

Cornerstone SuperTherm is a premixed dry lime plaster that serves as an exceptionally lightweight and low-density fibred basecoat, specifically intended for use in a minimum two-coat rendering system for interior spaces. This product is offered in a classic white shade.

Meticulously engineered, this internal lime plaster boasts outstanding insulating capabilities. It incorporates an advanced foamed aggregate featuring a nanometre pore structure, effectively reducing heat loss through the building’s outer layers. The plaster comes standard with reinforcing fibres and high-purity Calcium Hydroxide combined with pozzolan.

This solution is ideal for projects that demand an ultra-lightweight plaster with remarkable insulation features. With a measured K Value of 0.04, applying it at a thickness of 50mm can enhance the U value of a solid wall by over 75%.

Key Features

Cornerstones best performing insulating plaster
Engineered to enhance insulation while lowering heating costs.
Exceptional vapour permeability to aid moisture management.
Minimises relative humidity and prevents condensation.
Enhances indoor air quality and promotes thermal comfort.
Free from harmful halogens, VOCs, and heavy metals. Contains absolutely no toxic heavy metals.
Highly vapour permeable to assist with moisture control.
Can be applied in high-build layers of up to 50mm per pass.
Ultra-lightweight formulation for easier levelling and finishing.

Technical Information

Coverage Rate

After mixing with water, a bag will cover approximately 1.8-2 m2 at 10mm thickness.

Benefits

K-Value - 0.04 W/mK
Significantly warmer buildings
Reduced heating costs
Management of relative humidity and condensation within living areas
lightweight and easy to apply
Dry Hardened Density - 260kg.m3
sustainable and environmentally friendly plaster
Consistency of Product compared to site mixed alternatives

Product Test Data

Compressive Strength - 3.014N (EN1015-11)
Flexural Strength - 0.511N (EN1015-11)
Vapour Permeability - 4.2µ (EN1015)
Water Absorption - 1.8kg (EN1015-18)
Reaction to Fire Classification - B-s1, d0 (BS EN13501-1:2018)

Preparation

Best practice is where the surface is clean, free of dust and other debris.
The background should be adequately dampened when necessary to promote good adhesion and bonding with the base surface.
Absorbent backgrounds or materials require dampening before application to prevent rapid drying after application. Dense or impervious backgrounds or materials don't require dampening.
There is an in-depth application guide available that details the technical aspects of using SuperTherm. We recommend reading the document for tips and advice prior to purchase and application.

Mixing

Consistency: Prepare the plaster to achieve a workable texture, ensuring you do not add too much water. Excess moisture can weaken the plaster and reduce its thermal efficiency. Typically, more water is needed when using a spray application than when hand mixing. Adding additional water increases the risk of shrinkage, so proper curing and aftercare are essential.

SuperTherm can be mixed using a standard cement mixer or a plastering whisk set to a slow speed. Due to its lightweight composition, mixing with a whisk slows down the setting process and requires a longer curing period—about two weeks between coats, compared to one week when using a cement mixer.

For each 15-litre bag of SuperTherm, you will need approximately 4.5 to 5.2 litres of clean potable water. Note that water content may vary slightly between bags because of the aggregate's natural porosity; however, this will not impact the final strength of the finished wall.

Always mix SuperTherm using full bags—do not split bags into smaller portions. To mix, add roughly 80% of the required water first, then incorporate the dry plaster. Allow the mixture to blend for 1 to 2 minutes, then add any additional water as needed and continue mixing. Covering the mixer mouth is recommended to prevent powder splashing during operation.

When using a mixer, regularly check the consistency of the mixture every few minutes. Thanks to its lightweight nature, you may need to scrape down the sides and bottom of the mixer to ensure thorough mixing.

Once water is added, the mixture remains workable for approximately 1 hour and 20 minutes.

View the mixing and application guide for more in-depth information.

Application

Application of SuperTherm plaster involves a process similar to applying a standard base plaster coat. To maximize insulation efficiency, ensure the build-up is even throughout. Always finish with a meshed topcoat plaster layer for the best results.

Since SuperTherm is lightweight, it should not be pressed or worked into the substrate like traditional dense sand and lime plasters. Although it can be applied using a trowel in the conventional manner, pressing the material compresses it, slightly reducing its thermal performance, even though it doesn't compromise its structural integrity. For optimal insulation properties, spraying or casting is recommended.

During application, use a serrated edge to level the surface gently, avoiding overworking or compressing the material. Floating the plaster is discouraged to maintain performance.

Curing

For curing, a slow and steady approach yields the best results. Maintain a humid environment by misting the surface occasionally over the first 7-10 days to prevent rapid drying and support strength development.

SuperTherm gains strength gradually over the initial 2-3 days, with significant improvements following this period. Keeping the plaster moist during early curing is critical for achieving top insulation performance.

Temperature conditions should be controlled to ensure optimal application. It is best to apply SuperTherm when the ambient temperature ranges between 5°C and 25°C, and the surface should be protected from extreme heat or cold during curing.

Documents

Try our downloadable information below for in-depth guidance on application and product specification.

Links open in new tab