How to Choose Ground Mat Thickness
Thickness is a bending-stiffness decision, not just a load-rating decision. Use the ground condition and contact area to choose between 12.7 mm, 15 mm and 20 mm.
Catalogue load ratings are a poor way to choose a mat thickness. A thick panel on firm ground is wasted money; a thin panel on saturated clay will flex, lift at the edges and eventually crack even though its published rating looks adequate. The property you are selecting for is bending stiffness relative to the support the ground provides.
This page gives a repeatable method. It is a selection aid, not a structural design – lifting operations and public-safety structures need a competent engineer.
The four inputs you need
- EquipmentGross weight, axle or track layout, tyre pressure, and whether outriggers or stabilisers create point loads.
- Contact areaA crawler track or a wide tyre spreads load more than a narrow outrigger foot. Smaller contact areas need a stiffer panel.
- Ground bearing capacityDry granular soil, damp turf, saturated clay and peat behave very differently. If you cannot measure it, describe it conservatively.
- Duration and trafficHundreds of passes over a season is a different problem from one delivery on a dry day.
Selection table
| Ground condition | Traffic | Thickness | Connections |
|---|---|---|---|
| Firm, dry | Pedestrians, hand carts | 12.7 mm | Recommended on public routes |
| Firm, dry | Vans, pickups, small plant | 12.7 mm or 15 mm | Yes |
| Damp, moderately soft | Delivery lorries, skid steers | 15 mm | Yes, every seam |
| Saturated clay / peat | Excavators, loaded trucks | 20 mm + geotextile | Yes, every seam |
| Any | Crane outriggers, high point loads | 20 mm + engineering review | Yes |
| Uneven with deep ruts | Any vehicle | Regrade first, then 20 mm | Yes |
If the subgrade is so weak that it fails beneath the mat, a thicker panel will not fix it. Add separation geotextile, a granular working layer or a different route.
Why thickness changes behaviour
A mat works as a plate resting on an elastic foundation. Increasing thickness raises bending stiffness much faster than it raises weight, so a 20 mm panel spans soft spots that a 12.7 mm panel would follow into the ground. That is why step-up advice is about ground condition rather than headline load capacity.
The cost of going one gauge thicker is small compared with a cracked panel, a stuck machine or a delayed lift. When the ground is wet and the assessment is uncertain, choose the thicker option.
Common mistakes
- Selecting from the load rating alone and ignoring subgrade
- Using a thin panel on a long-duration haul route because it was only 'temporary'
- Leaving seams unconnected, so panels work individually instead of as a platform
- Driving over unsupported corners or edges – the leading cause of cracked mats
- Assuming a mat can bridge a trench or void; it is designed to sit on the ground
Frequently Asked Questions
Is a thicker mat always better?
No. On firm ground with light traffic a 12.7 mm panel is lighter, faster to lay and cheaper. Thickness buys bending stiffness, which you only need when the ground cannot support the load locally.
What thickness do I need for a 30 tonne excavator?
On soft or wet ground, start with 20 mm connected panels and assess the subgrade. On firm dry ground 15 mm may be adequate. Confirm with the track configuration and ground condition.
Can I mix thicknesses on one site?
It is possible by zone – for example 12.7 mm on pedestrian routes and 20 mm on the haul road – but avoid mixing thicknesses within a single continuous traffic platform, as the step creates an impact point.
Do crane outriggers need a special mat?
They need an engineered assessment. Our 20 mm panel is the starting point, but outrigger reaction forces and ground bearing capacity must be reviewed by a competent engineer, and we can supply material test data.
Related Resources
Need a mat specification for your site?
Tell us the equipment, ground condition and project duration. Our team will recommend the right size, thickness and connection layout, then send a quote with loading quantities and lead time.
Request a Quote Email albert@hdpegroundmat.com- Size and thickness recommendation for your load
- Loading plan, MOQ and lead time
- Samples and third-party test data on request