Why is my Render Cracking?

Worried about cracked render? It’s a common problem that may or may not be serious, dependent on the underlying cause. In this article the Logic Plastering team use look at the reasons why you may be experiencing render cracking, offer tips for proactive render maintenance, and suggest 3 types of render that are less likely to succumb to cracks.

Rendering, or external plastering, protects our homes and buildings in two ways. First, it insulates them against either extreme cold, or extreme heat. Second, it weatherproofs the brickwork, adding a protective layer to ensure that walls remain dry and durable. Cracked render creates vulnerabilities in this protective layer and heightens the risk of damp and crumbling brickwork.


What Causes Cracked Render?

There are several factors that can contribute to the development of cracks on the exterior surface of your property or building:

1. Settlement and Movement

Buildings naturally settle over time. This is due to changes in the moisture content of the soil on which the property is built, external temperature variations, and the settling of the building foundation. All these factors can create stress on the exterior rendering, leading to cracks.

2. Moisture and Water Ingress

If water seeps into your rendering it will weaken it and cracks will form. These cracks bring their own problems; they can allow water to become trapped between the render and brickwork. If this is allowed to build up it can lead to damp patches on internal walls.

3. Inadequate Preparation of Substrate

The durability of render is heavily dependent on the preparation of the substrate, the foundational surface upon which the rendering is applied. The substrate serves as the anchor point for the rendering material, and if the surface beneath the rendering is not properly prepared, with appropriate bonding agents and reinforcement, it can lead to poor adhesion and cracked render as a result.

4. Inferior Materials, or Inappropriate Application

The quality of the rendering materials used can affect its durability. The use of poor materials or mixing them incorrectly can result in a rendering that is more prone to cracking. Equally problematic is rendering that has not been applied evenly, or at the thickness required. This uneven application can lead to weak points in the surface, which are more likely to crack.

5. Structural Issues

Horizontal cracks in render can be caused by underlying structural issues. If the building is subject to subsidence, or if there are integral problems with the design of the building, such as inadequate expansion joints or improper placement of openings, this can result in stress concentrations that lead to cracked render.

If you suspect structural issues to be the problem causing cracks in your render, you will need to get a structural engineer to assess your building. They will be able to advise on appropriate remediations.

6. Vibrations

Vibrations generated by nearby construction or heavy machinery can reverberate through the building’s framework, placing stress onto the structure and increasing the risk of cracks in the render.

Render Maintenance to Avoid Cracking

Render Maintenance to Avoid Cracking

Maintaining rendering to prevent cracking needs a proactive approach. You should inspect the surface every few months for any signs of wear, moisture intrusion, or developing cracks. Ensure proper drainage and grading to prevent water accumulation near the rendering. A quality waterproof coating will protect your render from water penetration; if this wasn’t applied when the render was installed it can be applied at a later date.

Which Renders Are Less Likely to Crack?

Some renders are known for their enhanced resistance to cracking. This is because of their specific properties and composition. The most crack-resistant rendering options include:

  • Polymer-Modified Renders. These renders incorporate polymer additives that enhance flexibility, adhesion, and overall durability. They can better withstand temperature fluctuations and structural movements, reducing the risk of cracking.
  • Silicone Render. Silicone-based renders are highly flexible and water-resistant. They create a breathable yet waterproof barrier, allowing the substrate to expand and contract without compromising the rendering’s integrity.
  • Acrylic Render. Acrylic renders contain acrylic polymers that provide elasticity and improved adhesion. They are less prone to cracking, especially when applied over a well-prepared and reinforced substrate.

What Should I Do About Cracked Render?

The best time to deal with this problem is when you first notice hairline cracks. Logic Plastering would recommend calling in a professional external renderer. Why? Because they’ll be able to either diagnose the problem or suggest that you can in a surveyor for more detailed inspection of your building’s structure.

Hairline cracks are fairly simple to deal with. They need to be securely sealed in order to ensure that moisture can’t get between the render and the walls. Where your render has ‘blown’, or fallen away from the walls leaving brickwork exposed, the render repair is more extensive. All crumbling plaster needs to be hacked away and patches applied. Our Logic Plastering specialists are normally able to achieve invisible render repairs for customers.

About Logic Plastering

We’re a local business, based in Bedford, and we’ve been providing internal and external plastering for over a decade now. Our plastering team are all skilled and professional tradesmen with years of experience behind them. We provide a free, no obligation quotation on all jobs and always guarantee the work we do. Customers across Bedfordshire can trust us to arrive when we say we will, complete the work to deadline, and charge competitive rates for what we do.

If you’re worried about cracks in your rendering, one of the Logic Plastering team will be happy to come out and assess it. Call us today on 07809 228328