The short answer is yes, resin bound surfacing can often be laid over an existing surface, provided the existing construction is sound, stable and suitable for the new system.
For commercial projects, this can be a significant advantage. If an existing surface can be retained, it may reduce excavation, waste, disruption and installation time. However, not every existing surface is suitable for a direct resin bound overlay.
Before deciding whether to overlay or replace an existing surface, its condition, stability, drainage, levels and intended use all need to be considered. Cracks, movement or deterioration beneath the surface won’t simply disappear when resin bound surfacing is installed over the top.
What surfaces can resin bound be laid over?
Permeable or open-graded tarmac is typically used as the immediate base beneath resin bound surfacing, accompanied by an MOT Type 3 subbase. Other surfaces may require additional preparation or a new base before resin bound can be installed.
The important consideration isn’t simply what the existing surface is made from. It is whether that surface and the construction beneath it provide a suitable, stable base for the proposed resin bound system.
Can resin bound be laid over existing tarmac?
If the existing tarmac is permeable or open-graded, it can provide a suitable base for resin bound surfacing, as long as it is in good condition and capable of supporting the intended use of the area. Before overlaying, the existing surface should be assessed for issues including:
- Cracking
- Potholes
- Movement or settlement
- Loose or deteriorating material
- Contamination
- Poor drainage
- Uneven areas
- Damage to the underlying construction
Where the existing surface is sound, retaining it can potentially avoid the need for complete excavation and reconstruction. However, if the tarmac has failed, laying resin bound surfacing over it isn’t a solution in itself. The underlying problem should be addressed before the new surface is installed.
Can resin bound be laid over existing concrete?
No. HMS does not recommend installing resin bound paving directly over an existing concrete surface.
One of the key benefits of resin bound paving is its permeability, allowing water to pass through the surface and into the construction below. Concrete is impermeable, so installing resin bound paving over concrete prevents water from draining freely through the complete system.
Even where falls or additional drainage are introduced, there is still a risk of water becoming trapped between the resin bound surface and the concrete beneath it. Over time, trapped moisture can compromise the system and increase the risk of surface failure.
For this reason, an existing concrete surface would need to be removed and replaced with a suitable construction before resin bound paving is installed.
A typical permeable build-up may include a suitable permeable sub-base, such as MOT Type 3, followed by an open-graded/permeable asphalt base and the resin bound paving system.
This allows water to drain through the resin bound surface and the layers beneath it, rather than becoming trapped within the construction.
Can resin bound be laid over block paving?
No. Block paving isn’t a suitable base for resin bound paving and shouldn’t be directly overlaid.
Unlike a continuous asphalt base, block paving is made up of individual units that can move independently over time. Movement, settlement and the joints between the blocks can create an unstable substrate beneath the resin bound surface, increasing the risk of cracking and failure.
Even where existing block paving appears to be in good condition, it doesn’t provide the stable, continuous base required for a correctly specified resin bound paving system.
For a commercial resin bound installation, the block paving should be removed and the construction assessed before installing an appropriate base. Where a fully permeable system is required, this would typically involve a suitable permeable sub-base and open-graded/permeable asphalt before the resin bound surface is installed.
Removing an apparently sound surface can add to the initial programme, but creating the correct base is essential to the long-term performance of the resin bound paving.
Can resin bound be laid over gravel?
Loose gravel isn’t a suitable surface for a direct resin bound overlay. Resin bound surfacing requires an appropriately designed and stable base. Simply installing it over loose aggregate wouldn’t provide the necessary support for the finished surface.
Where an area is currently gravelled, additional construction work will generally be required to create a suitable base before the resin bound surface is installed.
When is an existing surface suitable for overlaying?
The decision needs to be made on a project-by-project basis, but there are several important considerations.
Is the existing surface permeable and structually sound?
A suitable permeable tarmac surface may be retained if it is in good condition. Concrete, block paving, paving slabs and loose gravel aren’t suitable surfaces for a direct resin bound overlay and should not simply be covered with resin bound paving.
The surface and construction beneath it need to be capable of supporting the anticipated use.
A pedestrian footpath, public space and vehicle access area can place very different demands on a surfacing system, so the intended application needs to form part of the assessment.
Is there existing cracking or movement?
Cracks can indicate movement or failure within the existing construction. Covering them with a new resin bound finish doesn’t necessarily prevent that movement from continuing.
The cause and extent of cracking should therefore be understood before deciding whether remediation or replacement is required.
Are there localised areas of failure?
A small number of damaged areas doesn’t necessarily mean the entire existing surface needs replacing. Depending on the condition of the site, localised repairs may be possible before the resin bound system is installed.
This can be particularly valuable on larger commercial schemes where most of the existing construction remains in good condition.
What will happen to the finished levels?
Overlaying an existing surface increases its finished height. This needs to be considered around:
- Kerbs
- Doorways and thresholds
- Drainage channels
- Manholes and utility covers
- Steps
- Edging
- Adjoining surfaces
These details need to be considered before installation rather than addressed once the resin bound surface is being laid.
What about drainage?
One of the major characteristics of resin bound surfacing is its permeability.
However, it’s important to distinguish between a permeable surface and a fully permeable construction.
Water can pass through the resin bound layer, but what happens next depends on the construction beneath it.
If resin bound is installed over an impermeable existing surface, such as concrete, water can’t simply continue vertically through the entire construction. Appropriate falls and drainage may therefore be required. HMS doesn’t recommend this as water may become trapped between the layers and cause the system to fail.
Where permeability and sustainable drainage form part of the project requirements, the entire construction needs to be considered.
When should an existing surface be repaired rather than replaced?
Remediation can sometimes provide a more efficient alternative to completely removing an existing surface.
For example, if the majority of the tarmaced area is sound but a small number of sections have deteriorated, those areas may potentially be repaired before the resin bound surface is installed. The appropriate approach depends on the cause and extent of the damage.
Localised deterioration is very different from widespread cracking, settlement or structural failure.
The objective shouldn’t be to retain as much of the existing surface as possible at all costs. It should be to retain what’s suitable and remediate or replace what’s not.
What are the advantages of overlaying an existing surface?
Where the existing surface is suitable, overlaying can offer several advantages on a commercial project.
It may reduce the amount of material that needs to be excavated and removed from site, potentially reducing waste and vehicle movements. Less reconstruction may also mean a shorter programme and reduced disruption. This can be particularly valuable when surfacing:
- Public spaces
- Commercial developments
- Footpaths
- Parks
- Schools
- Housing developments
- Courtyards
- Pedestrian areas
- Cycle routes
Where sites need to remain operational or access needs to be maintained, the ability to retain an existing base can make project planning considerably easier.
But overlaying isn’t always the best option
The potential time and cost savings shouldn’t be the deciding factor if the existing construction isn’t suitable. Installing a high-quality resin bound finish over an unstable or deteriorating base can result in problems developing later.
This can ultimately mean further remedial work, additional cost and more disruption than would have been required to address the underlying problem during the original installation.
For commercial projects, looking at the whole-life performance of the surface is therefore more important than simply finding the quickest installation method.
Overlay, remediate or replace?
Before installing resin bound surfacing over an existing surface, ask:
- What is the existing surface made from?
- Is it structurally sound?
- Are there cracks or signs of movement?
- Are there potholes or failed areas?
- Is deterioration localised or widespread?
- What will the finished area be used for?
- What loading will the surface experience?
- How will the overlay affect finished levels?
- How will water drain?
- Can damaged areas be remediated?
- Would a new base provide a more appropriate long-term solution?
The answers will help determine whether the existing surface can be retained, requires remediation or should be replaced.
Assess the surface before deciding
So, can resin bound surfacing be laid over existing surfacing?
Yes, in some cases it can. Sound tarmac or appropriately prepared concrete can potentially provide a suitable base for resin bound surfacing. Other existing surfaces may require more extensive preparation, stabilisation or replacement before installation.
The key is to assess what’s already there rather than assuming that either complete excavation or a direct overlay is automatically required.
For contractors, developers, local authorities and other commercial clients, this can help identify a solution that balances programme, disruption, cost and long-term performance.
Looking for a resin surfacing contractor?
HMS Decorative Surfacing has extensive experience delivering resin bound surfacing for commercial developments, public realm schemes, footpaths, parks and other public spaces.
Planning to upgrade an existing surface? Speak to HMS Decorative Surfacing about your project. We can help determine the appropriate preparation and resin bound surfacing solution for your site.
