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Why Do Resin Bound Surfaces Crack and How to Fix Them?

Resin Surfacing has gained immense popularity in recent times. Despite its many advantages, it's still a relatively new addition to the hard landscaping market. Over the years, I've observed numerous instances of cracks appearing in resin surfaces. This article aims to shed light on this issue, benefiting both contractors and end-users.

Contractor applying resin bound surfacing to a concrete surface for a back garden patio space.

Understanding the Basics of Resin Bound Surfacing

Resin bound surfacing is an in situ bonded screed, implying that it's bonded directly to the substrate. This means that the fate of the resin surface is intertwined with that of the substrate. While cracks in the resin bound surfacing are visible symptoms, they are not the root problem.

Let's delve into the five most prevalent reasons behind the cracking of resin bound surfaces:

1. Reflective Cracking from Different Types of Adjoining Substrates

What is it? When different substrates, like an asphalt base adjoining a concrete base, are combined, or when a new concrete slab is laid next to an aged one, reflective cracking can occur. These substrates have different curing profiles, leading to movement, tension, and eventually, cracks in the resin bound surface.

How to fix it? The most reliable solution is to replace all existing substrates with a new, open-grade asphalt surface. If that's not feasible, consider using an expansion joint trim or segregating areas with an internal border. If overlaying different substrates is unavoidable, remedial work at the joint using an epoxy and a jointing mesh can help.

2. Cracking from Intrusions Called Re-Entrant Cracking

What is it? Re-entrant Cracking, a common yet often misunderstood cause of cracking, occurs due to stress forces concentrating on a single point, especially at acute angles. As Tony McCormack from Paving Expert explains, these stress forces seek the shortest path to relieve pressure, leading to cracks.

How to fix? While fine hairline cracks can be repaired using a thickened resin, the best approach is prevention. Avoid any intrusions that disrupt the shape of a resin bound area.

3. Application onto Surfaces Not Designed to be a Base

Resin bound surfaces require a hard base like asphalt or concrete. However, not all hard surfaces, like block paving or crazy paving, are suitable. These surfaces may to move, which can lead to cracks in the resin bound surfacing.

How to fix? For areas with vehicle traffic, overlaying such substrates is not recommended. While some opt for overlays in gardens or patios with limited use, it comes with risks.

4. Reflective Cracking Caused by Expansion Joints or Existing Cracks

What is it? Overlaying concrete substrates can lead to reflective cracking, especially if the concrete has induced joints designed to move. Such movement can cause cracks in the resin bound surface.

How to fix it? While replacing with an asphalt substrate, there are other solutions. One can repair existing cracks with high-strength epoxy mortar. For larger, structural joints, installing an expansion joint is recommended.

5. Failure or Subsidence of a Sub-Base and/or Base

The sub-base, usually MOT Type 1 or 3, lies beneath the base on which the resin bound surface is applied. Any failure in these can lead to subsidence and cracks in the resin bound surface.

How to fix? The best approach is to replace the base and sub-base of an existing project. If that's not possible, ensure the base is solid before applying the resin bound surfacing.

In Conclusion: Key Takeaways from Resin Bound Surfacing Issues

Resin bound surfacing, while a remarkable addition to the landscaping domain, does come with its set of challenges. To ensure the longevity and beauty of your resin surface, it's essential to be aware of potential pitfalls. Here's a quick recap of the issues discussed:

Reflective Cracking from Different Substrates:

  • Caused by adjoining different types of substrates.

  • Watch out for areas where new and old substrates meet.

Re-Entrant Cracking:

  • Stress cracks often found where acute or right-angle intrusions occur.

  • Be cautious of areas with sharp angles or intrusions.

Unsuitable Base Surfaces:

  • Not all hard surfaces are suitable for resin bound surfacing.

  • Avoid using block paving or crazy paving as a base.

Cracking from Expansion Joints:

  • Movement in concrete joints can reflect as cracks in the resin surface.

  • Be wary of overlaying concrete with visible joints or cracks.

Sub-Base and Base Failures:

  • Subsidence in the base or sub-base can lead to surface cracks.

  • Ensure a solid foundation before application.

In essence, while resin bound surfacing is a fantastic choice for many landscaping projects, it's crucial to be informed and vigilant. By understanding potential issues and taking preventive measures, you can ensure a crack-free, stunning resin surface for years to come. Always consult with a professional when in doubt, and prioritise quality and expertise over shortcuts and quick fixes.

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