11/08/2026
Why do we think the render failed?
There are a number of factors that can contribute to the failure of a lime render, including an incorrect mix, insufficient hair reinforcement, inadequate mechanical fixing, a poor key between coats, or unsuitable weather conditions during application and curing. At the outset, therefore, there were several possible causes.
However, once the failed render was removed, we were able to identify a number of specific issues with the existing work:
Image 2 – Lack of hair reinforcement: There was insufficient hair within the lime mix. Hair is an important component of traditional lime plaster/render, providing reinforcement and helping to control movement and cracking.
Image 3 – Poorly fixed laths: The laths were inadequately fixed, compromising the mechanical support for the render.
Image 4 – Lack of key in the scratch coat: The scratch coat had not been adequately keyed, reducing the mechanical bond between the coats and increasing the likelihood of delamination.
Image 5 – Inadequate fixings: The fixings used were insufficient to provide the required support and stability to the lath.
Image 6 – Our fixing method: As part of the replacement works, we only use stainless-steel ring-shank nails to fix our laths, providing a secure mechanical fixing suitable for the application.
We also only use UK-sourced hair in our lime mixes, ensuring appropriate reinforcement within the mix.
While factors such as the mix specification and the weather conditions at the time of the original application may also have contributed to the failure, the defects identified during removal provide clear evidence of deficiencies within the original lath and render.
Our approach to the re-render is therefore to address these issues at the substrate and fixing stage, as well as using the correct lime mix and reinforcement, so that the new render has the best possible opportunity to perform as intended.
