When it comes to modern insulation systems, achieving a durable, breathable and aesthetically consistent finish is just as important as thermal performance. K Rend LW1 lightweight render has become a go‑to solution for contractors and specifiers looking to achieve a scratch render finish on external wall insulation (EWI) systems with excellent workability and long‑term performance.
In this Blog, we’ll explore what K Rend LW1 is, why it’s ideal for insulation systems, and how it can be used to achieve a professional scratch render finish, while maximising durability and visual appeal.
What Is K Rend LW1?
K Rend LW1 is a cement‑based, polymer‑modified, lightweight render designed for direct application onto both masonry and insulation substrates. It is self‑coloured, reducing the need for decorative coatings, and is fully compliant with BS EN 998‑1, CE marked and Kitemarked.
Key features of K Rend LW1 include:
- Lightweight formulation for easy application
- Suitable for EPS, mineral wool and phenolic insulation
- High coverage rates compared to traditional renders
- Hand or machine application
- Excellent adhesion and flexibility
These properties make K Rend LW1 especially well suited to external wall insulation systems, where substrate movement and breathability must be carefully managed.
Why K Rend LW1 Is Ideal for External Wall Insulation (EWI)
External wall insulation systems require a render that can accommodate thermal movement, resist cracking and maintain a consistent finish over large façades. K Rend LW1 is specifically designed to meet these demands.
Key Benefits for Insulation Systems
- Direct application onto insulation boards including EPS and mineral wool
- Two‑pass application system with embedded reinforcing mesh for impact resistance
- Nominal thickness of 12–16mm on insulation, ensuring strength without unnecessary weight
- Lightweight composition, reducing strain on the insulation system
- Breathable yet water‑resistant (W2 classified) for long‑term façade performance
These characteristics allow K Rend LW1 to perform exceptionally well as part of a complete EWI render system.
Can K Rend LW1 Be Used for a Scratch Render Finish?
Yes – K Rend LW1 is highly suitable for achieving a scratch (textured scraped) render finish on insulation systems.
While often associated with contemporary scraped or roughcast textures, LW1’s aggregate structure and open working time make it ideal for producing a uniform scratch finish when applied correctly.
How to Achieve a Scratch Render Finish with K Rend LW1
1. Surface Preparation
Ensure insulation boards are:
- Securely fixed
- Flat and level
- Free from dust and contaminants
Fix alkali‑resistant reinforcing mesh across the façade, with additional mesh around openings, corners and other stress points.
2. First Pass Application
- Apply the first coat at approximately 6mm thickness
- Embed reinforcing mesh into the wet render
- Ensure full coverage with no mesh visible
This base layer provides the structural strength required for the scratch finish.
3. Second Pass Application
- Apply a second pass of approximately 8mm on insulation systems
- Rule off to achieve a flat and consistent surface
- Do not polish – this is crucial for textured finishes
The total finished thickness should not be less than 12mm on insulation substrates.
4. Scratching Process
The scratch finish is achieved during the textured scraping stage:
- Allow the render to firm up until:
- A thumb impression cannot be made
- Aggregate scrapes cleanly without dragging
- Using a scratching tool or scraper, work in tight, consistent circular motions
- Brush down the surface with a soft brush once complete
Timing is critical:
- Early scraping results in darker shades
- Late scraping produces lighter tones
Consistency across the entire elevation is essential for a uniform appearance.
Design Flexibility and Aesthetic Appeal
K Rend LW1 is available in an extensive range of colours, allowing scratch render finishes to suit both traditional and contemporary designs. Because it is self‑coloured, the finish maintains its appearance without ongoing decoration, lowering maintenance costs over the building’s lifespan.
A sample panel is always recommended to:
- Confirm colour choice
- Assess texture
- Agree finish quality with the client
Performance and Durability
From a performance perspective, K Rend LW1 delivers:
- CS III compressive strength
- Thermal conductivity of 0.30 W/mK
- Strong resistance to water penetration
- Long‑term colour stability
When applied within the manufacturer’s guidelines and protected during curing, a scratch render finish using K Rend LW1 offers excellent durability, even in exposed environments.
Ideal Applications for K Rend LW1 Scratch Render
- Residential external wall insulation systems
- Retrofit insulation upgrades
- Low‑rise commercial buildings
- New‑build housing developments
- Façade refurbishment projects
Final Thoughts
If you’re looking to achieve a high‑quality scratch render finish on an external wall insulation system, K Rend LW1 is a proven, specification‑grade solution. Its lightweight formulation, compatibility with insulation substrates and ease of texturing make it an excellent choice for contractors aiming for both performance and visual consistency.
When installed correctly, K Rend LW1 delivers a durable, breathable and attractive scratch render façade that stands the test of time.
Shop LW1 Now
Disclaimer: The above is a high-level breakdown for a specified render system and was fully up to date and correct at the time of writing. Whilst we endeavour to ensure this page is kept up to date in line with any changes made by the manufacturer, we strongly recommend customers verify the above information directly with the manufacturer prior to a making a purchase or the application of any products and do not rely solely on the information provided above when making a decision. We accept no liability or responsibility for losses or damages occurring as a result of a customer’s failure to comply verify the above information. The render system should be applied in strict accordance with the manufacturer's instructions and specifications. These can be obtained directly from the manufacturer.