If you’re planning a new car park, upgrading an access road or resurfacing your commercial yard, you’ll want to know whether the proposed asphalt thickness is suitable.
Your surface needs to support your daily operations without leaving you facing premature repairs. But an office car park and a busy delivery yard, for example, have very different demands.
At MR Surfacing, we’ll assess your site and how you’ll use it before recommending an asphalt specification. Here’s what determines the thickness you’ll need.
What does asphalt thickness include?
First, check which layers you’re discussing. The visible top layer, called the surface course, provides the finish that vehicles and pedestrians use. Beneath it, a binder course adds support, with an additional asphalt base included when the design requires it.
Below the asphalt sits the foundation, which includes a compacted granular sub-base and, where needed, a capping layer to provide additional support over weaker ground.
How thick should commercial asphalt be?
To give you an idea of the depths involved, here are three example asphalt constructions for different types of vehicle use:
- Small office car park: A 30mm surface course over a 60mm binder course gives 90mm of asphalt, supported by a suitable compacted granular foundation.
- Medium-weight lorry parking (payloads of up to about 5 tonnes): A 40mm surface course, 60mm binder course and 100mm asphalt base give a total asphalt thickness of 200mm.
- Heavy lorry parking: Increasing the asphalt base to 150mm beneath the same surface and binder courses brings the total to 250mm.
If your project involves work on the public highway or a new road intended for council adoption, we’ll check the relevant highway authority’s specification. Requirements can vary across the Midlands. Industrial access road specifications usually require somewhere around 300mm of asphalt across all layers, for example.
How does vehicle use affect asphalt thickness?
Tell us about your delivery vehicles, refuse collections and maintenance access as well as your everyday traffic. We’ll also need to understand where vehicles turn, brake and stand.
Slow-moving and stationary lorries can place greater stresses on the surface than vehicles travelling at normal road speeds. Forklifts and trailer support legs introduce concentrated loads that may require specialist materials or concrete sections.
What’s underneath the asphalt?
If your site has soft clay, poorly consolidated fill or wet ground, the foundation design must account for that. We may use a California Bearing Ratio test to assess the ground’s strength and help determine how deep your foundation needs to be.
Depending on the findings, you may need deeper granular layers, capping or ground improvement.
Your sub-base and drainage need to be planned together. The finished levels should direct rainfall towards suitable drainage, while the design must also account for water below the surface.
Does resurfacing mean replacing every asphalt layer?
If the supporting layers are still sound, planing and replacing the worn surface course may be sufficient. However, sinking areas or widespread cracking may indicate deeper weakness. Those sections need investigating before new material is laid.
What should your surfacing quote include?
Look for the compacted thickness and asphalt type for each layer, along with the proposed groundwork, drainage and treatment of existing defects. The specification should account for the traffic you’ve described.
Thickness alone won’t give you a durable surface. Asphalt also needs to be laid and compacted correctly, with suitable bonding between layers.
Frequently asked questions
How thick should asphalt be for a commercial car park?
It depends on the vehicles using it. A small office car park might have a 30mm surface course over a 60mm binder course, giving 90mm of asphalt on a compacted granular foundation.
How thick should asphalt be for lorry parking?
Medium-weight lorry parking could use a total of 200mm of asphalt, while heavy lorry parking could increase the asphalt base to 150mm for a total of 250mm.
How is ground strength assessed before asphalt surfacing?
A California Bearing Ratio test may be used to assess the ground's strength and help work out how deep the foundation needs to be. Depending on the findings, deeper granular layers, capping or ground improvement may be needed.
Does resurfacing mean replacing all the asphalt layers?
Not always. If the supporting layers are still sound, planing and replacing the worn surface course may be enough, but sinking areas or widespread cracking may point to deeper weakness.
Is asphalt thickness enough to guarantee a durable surface?
No. Asphalt also needs to be laid and compacted correctly, with suitable bonding between layers.
Get the right specification for your commercial site
You don’t need to knock on our door and ask us for a full resurfacing if you haven’t reached that point yet. Bring us your plans, explain how your premises operate and tell us what you need to improve.
We’ll help you understand the options for your car park, access road or yard, including the preparation needed before surfacing begins.
Contact MR Surfacing to arrange a free, no-obligation consultation, or call 0116 216 2372 to discuss your project.