Cracked Render and Damp on External Walls. Causes, Problems and Long Term Solutions
- Sam - PlasterSmart
- 3 days ago
- 4 min read
Cracked Render and Damp on External Walls. Causes, Problems and Long Term Solutions
Cracked render on external walls is one of the most common issues we see on older properties across Surrey. Many homes were originally rendered using strong sand and cement mixes that were never designed to work with softer, traditionally built masonry. These rigid renders are not very flexible and, over time, natural building movement and temperature changes cause cracks to form.
In many cases, these older renders have also been painted with non breathable masonry paints. Once cracks appear, rainwater inevitably finds its way into the render and masonry behind. Because both the paint and the render are dense and non breathable, moisture becomes trapped within the wall rather than being able to dry out naturally. Over time, this moisture can migrate inwards and start to show internally as damp patches, peeling paint, blown plaster and mould growth. This is one of the most common causes of penetrating damp we come across.
Why traditional sand and cement render often fails long term
Traditional sand and cement render requires ongoing maintenance to perform well. Cracks need to be regularly filled and the paintwork needs to be kept on top of, often every few years. In reality, most homeowners understandably do not keep up with this level of maintenance. Cracks are left, water continues to get in, and problems slowly worsen over time.
Even where repairs are carried out, properties can end up looking like a patchwork quilt of filled cracks and repainted areas. This is rarely a long term solution and often just delays more serious problems developing beneath the surface.
The best long term solutions for cracked render
The right solution depends on how far the problem has progressed and the condition of the existing render and wall beneath. There is no one size fits all fix, which is why proper assessment is important.
Filling cracks and patch repairs to existing render:
For homeowners working to a tighter budget, filling visible cracks and carrying out localised patch repairs to damaged areas of render can help reduce immediate water ingress and slow down penetrating damp issues. This approach can be effective as a short term measure to deal with obvious entry points for moisture.
However, this is not a long term solution. Traditional sand and cement render remains rigid and prone to future cracking as the building continues to move and respond to temperature changes. Ongoing repainting is also required to maintain any water resistance. Over time, new cracks will often appear in other areas, meaning regular maintenance and further patch repairs are usually needed.
Cork render overspray over existing render:
Where the existing render is generally sound and well bonded but suffers from widespread cracking, a cork based render overspray can be one of the most cost effective long term solutions. Cork render can be applied directly over stable existing render. It is highly flexible, which helps prevent future cracks reflecting through. It is also breathable, allowing trapped moisture to escape over time rather than becoming locked into the wall. This system comes with long term durability and is available in a range of colours, removing the need for regular repainting. It also improves the thermal performance of external walls, helping to reduce heat loss through the wall surface. Any loose or blown areas of render would be repaired first before application. As an overspray, existing undulations in the wall may still show through, although cork can also be applied as part of a full render system with a base coat where a flatter finish is required.
Full removal and replacement of failed render:
Where cracking has been left for many years, the render may have become blown in areas and the underlying wall saturated. In these cases, full removal of the existing render and replacement with a more appropriate breathable render system is often the best long term solution. This involves more work but provides a full external upgrade and a much more durable, long lasting finish for the property.
External wall insulation over existing render (where suitable):
In some situations, it may be possible to install an external wall insulation system over an existing rendered property. This can avoid the need for full render removal and provides a significant improvement in thermal performance. However, careful inspection is essential to ensure that moisture is not already trapped within the wall. The system must be designed correctly to avoid creating further moisture problems.
Not sure which option is right for your home?
If you are unsure what is causing the cracks in your render or whether moisture is already getting into your walls, we are happy to take a look and talk you through the most suitable options for your property.
We assess the condition of the existing render, check for signs of trapped moisture and advise on the most appropriate long term solution, whether that is targeted repairs, a cork render overspray, full render replacement or external wall insulation where suitable.
Contact PlasterSmart to discuss your cracked render and possible solutions
Our approach
We assess each property individually to understand the causes of cracked render, the current condition and stability of the existing render, and whether there is any evidence of moisture ingress or trapped moisture within the wall. This allows us to recommend solutions that are appropriate for the construction of your home and the severity of the issue.
We often provide a range of options based on budget and whether you are looking for a short term repair or a long term upgrade. This can range from localised render repairs, cork render overspray, full render replacement systems, through to external wall insulation where appropriate.
We cover homes across Surrey including Chertsey, Addlestone, Weybridge, Shepperton, Walton on Thames, Woking, Staines, Egham, Esher, Sunbury on Thames, Cobham and more.
If you have cracked render and are concerned about damp, mould or cold walls, we are happy to offer honest advice on what options may be suitable for your property and provide clear quotations for long term solutions rather than short term cosmetic fixes.
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