Gravel Car Parks - Permeable Parking Grids
Gravel Car Parks
A permeable car park that stays flat. IBRAN grids confine the stone so the surface takes daily traffic, drains where it falls, and satisfies the drainage strategy without a drop of tarmac.
Why reinforcement matters here
Loose gravel fails fastest exactly where a car park works hardest: turning circles, bay entrances, the approach to a barrier. Stone migrates under braking and steering, ruts form in the wheel paths, and within a season you are back with another delivery of aggregate.
A cellular grid confines the stone so it cannot move. Load still passes through the aggregate into the ground beneath, but the stone stays interlocked and stays where it was laid. That turns gravel from a surface you maintain into a surface you specify.
It also drains. On a commercial site that is rarely a nice-to-have: it is usually the condition attached to the permission.
Where this works well
- Commercial and staff car parks
- Retail, hospitality and visitor parking
- Service yards and delivery areas
- Access roads and internal site roads
- Farm, rural and estate parking
- Overflow bays alongside existing hard standing
- Accessible bays and pedestrian routes
At a glance
| Sub-base | 150-200mm compacted MOT, depending on traffic and ground conditions |
| Infill | 6-20mm graded blend, angular and clean, filled level plus a 5-10mm blinding |
| Typical loading | Cars, vans, delivery vehicles and occasional HGV movements |
| Permeability | Fully permeable. Normally treated as a SuDS component in a drainage strategy |
| Accessibility | A densely packed graded fill gives a firm, level surface suitable for accessible bays and routes |
| Bay marking | Contrasting aggregate, or bay markers fixed into the grid |
| Design life | 25 years, subject to documented installation |
| Material | 100% recycled polypropylene, made in the UK |
How it goes in
- Set out the area and establish falls. Even a fully permeable surface wants somewhere for a cloudburst to go, and levels are far easier to fix now than after the sub-base is in.
- Excavate to the depth of your sub-base plus the grid depth plus the infill blinding. Remove soft spots rather than building over them.
- Lay a woven geotextile across the formation, lapping joins by at least 300mm, so the sub-base and the subsoil cannot mix and the depth you have paid for stays where it is.
- Lay and compact the sub-base in 50mm layers. Compacting the full depth in one pass does not work, whatever the compactor.
- Blind with a thin layer of grit sand and screed it level.
- Push-fit the grids together across the area, working from one edge and staggering the joints. Cut around drainage, kerbs and lighting columns with a jigsaw or fine-tooth saw.
- Restrain every open edge. On a car park the perimeter takes load the interlocked field does not.
- Fill the cells with a 6-20mm graded blend, level plus a 5-10mm blinding, and work it in with a stiff brush so no cell is left hollow.
Full step-by-step detail is in our gravel grid installation guide.
Choosing your stone
Use a graded blend of 6-20mm, angular and clean. Most guidance points you at a single size, and a single size leaves voids: uniform stone bridges against itself and never quite packs solid. A blend fills those gaps, because the smaller stone wedges in between the larger.
On a car park that matters twice over. A fully bedded cell puts load through the stone and into the ground beneath; a part-filled cell puts it through the plastic instead. And a densely packed surface is a firm one, which is what makes gravel viable for accessible bays and pedestrian routes rather than something to apologise for.
Ask your merchant for washed graded aggregate, angular rather than rounded. Avoid fines and scalpings: they bind the surface and cost you the permeability the drainage strategy is relying on.
Marking out bays
You cannot paint a line onto gravel, but you have two better options.
Contrasting aggregate is the simplest: fill the bay divisions with a different colour stone as you go. It needs no maintenance, cannot be scuffed off, and looks deliberate rather than municipal.
Alternatively, bay markers fix directly into the grid, giving a defined edge for bays, accessible spaces and pedestrian routes. Both approaches survive far longer than paint on tarmac, which is worth factoring into the whole-life cost.
Which grid depth?
The number on a grid is a decision about how deep the confined stone layer is, and on a commercial site that decision usually belongs to the drawing rather than to preference.
- IBRAN®-X50 is our recommendation for commercial car parks. Use it where a specification calls for a deeper confined layer, where traffic is daily rather than occasional, or where you want design margin on a surface that has to stay flat for decades.
- IBRAN®-X40 for lighter-use car parks, staff parking and rural sites without sustained commercial traffic.
- IBRAN®-X30 where you are surfacing over existing concrete or tarmac, or finished levels are constrained by thresholds and drainage.
If you are between two options, take the heavier duty one. The cost difference across a car park is small next to closing it to relay the surface.
Get it right first time
The one thing worth knowing: build the sub-base properly, in layers.
Everything above the sub-base can be corrected. Stone can be brushed back level, a grid can be lifted and reset, an edge can be restrained after the fact. A sub-base compacted in one pass rather than in 50mm layers cannot be fixed without taking the surface up, and it will show as settlement in the busiest parts of the car park within the first two winters.
It is the cheapest part of the job to get right and by far the most expensive to get wrong.
Common Questions
Is a gravel car park suitable for daily commercial traffic?
Yes, when the stone is confined in a cellular grid and the sub-base is built for the loading. Load passes through the aggregate into the ground beneath, and the cell walls stop the stone migrating under braking and steering.
Specify against the heaviest vehicle that will use the site rather than the average, and use the 50mm grid where traffic is daily rather than occasional.
How do you mark out parking bays on gravel?
Two options, both better than paint. Fill the bay divisions with a contrasting colour aggregate as you lay, which needs no maintenance and cannot be scuffed off. Or fix bay markers directly into the grid for a defined edge on bays, accessible spaces and pedestrian routes.
Both outlast line marking on tarmac, which is worth factoring into the whole-life cost.
Is a gravel car park wheelchair accessible?
A stabilised gravel surface filled with a densely packed graded blend gives a firm, level surface suitable for accessible bays and pedestrian routes.
The key is the fill. A graded blend packs solid, where single-size stone leaves voids that castors and walking aids drop into. Loose unconfined gravel is not suitable.
Does a gravel car park count towards SuDS requirements?
A stabilised gravel surface is fully permeable, so water infiltrates where it falls rather than running off into a drainage network. It is normally treated as a component within a wider drainage strategy.
Permeability depends on the fill being clean and free of fines, which is why the stone specification matters as much as the sub-base.
What sub-base does a gravel car park need?
150mm to 200mm of compacted MOT, depending on traffic and ground conditions, laid and compacted in 50mm layers.
Compacting the full depth in one pass does not work whatever the compactor, and an under-built sub-base shows as settlement in the busiest parts of the car park within the first two winters.
What size gravel should a car park use?
A graded blend between 6mm and 20mm, angular and washed. A blend packs tighter than a single size because the smaller stone fills the gaps between the larger, and a fully bedded cell puts load through the stone rather than through the plastic.
Avoid rounded shingle, which rolls rather than interlocking, and anything carrying fines, which binds the surface and costs you permeability.
How does the cost compare to tarmac?
Installed cost is typically lower, and the whole-life difference is larger still. There is no resurfacing cycle, no crack repair and no line repainting, and the permeability often removes the need for the additional drainage infrastructure an impermeable car park requires.
Materials and groundworks vary by site, so ask us for a build-up and quantities against your area.
Can you lay grids over an existing tarmac or concrete car park?
Yes, provided the existing surface is sound and you have somewhere for water to go. Fill any holes, check your finished levels against thresholds and drainage, and use the 30mm grid to keep the build-up shallow.
If the existing surface is badly broken it usually has to come up, because breakage normally means the base beneath has already failed.
Do gravel car parks need edging?
Every open edge should be restrained. The perimeter takes load that the interlocked field does not, so without restraint the outer grids lift, spread and separate over time.
Use ramp edging at entrances and against thresholds, and edging strips where the surface meets soft ground.
How much maintenance does a gravel car park need?
Very little. Check levels after the first winter and brush any settled cells back up. Because the stone is confined it does not migrate, so there is no raking, no annual top-up and no resurfacing cycle.
The grid carries a 25 year warranty subject to documented installation.
Ask our engineer
Questions about depths, sub-base, edging or which system fits your project? Ask below.
