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Common Claims - Render Failure

We all learn from our mistakes so we thought we would take that theory and let you learn from others so you can avoid problems for yourself and the homeowner in the future. Our Technical Team have put together this advice to help you understand real life defects and the issues surrounding them.

Type of claim: Render is a popular solution to improve aesthetics or provide weather protection to a property but we get approximately 20 claims a year complaining of render failure.

How does this defect occur?

This defect can occur:

  •          if there is a lack of movement allowance
  •          incorrect mixing
  •          inadequate thickness
  •          wrong mix for the underlying surface

Implications of this type of defect: Issues range from cracking and de-bonding, which only gets worse as water gets in behind the render and becomes trapped. Others include complete detachment and/or water ingress through poor detailing or inadequate thickness or type of mix.

How can this be avoided from the outset? The main issue is selecting the correct render for the application, then ensuring detailing is correct. Some render systems fail due to poor weatherproofing at tops of walls, or around the opening and the base of walls, so it’s important that the other systems in place are correctly installed such as wall capping, parapet, roof covering and lead work. The render should be considered at design stage and the amount of exposure, type of construction and movement should be reviewed.

What are the early signs of this defect?

Hairline cracking, and localised discolouration on the render surface. You can also look out for a hollow sound when tapped.

Can this be prevented from worsening?

Unfortunately if it’s showing signs of failure then occasionally a patch can work but otherwise the only real solution is to start again.

Estimated costs of this type of claim: £££ (Key; Low £ - £££ High)

This type of claim can be costly as it usually involves stripping off render and re-applying, in some cases additional work will be required to the rest of the weatherproof envelope.

How can you learn from this?

It’s important to understand that rendering is increasingly becoming a specialist job and not something anyone can do. To ensure your render is adequate we would advise you thoroughly consider it at design stage and employ someone with experience to do it.

Further information: Please see Chapter 7, External Masonry Walls

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