CPS technical guide · reviewed 19 July 2026
HIAB pad size starts with the stabiliser reaction
There is no responsible one-size answer for a HIAB or lorry loader. Start with the highest verified stabiliser reaction for the planned operation, the assessed capacity of the ground or supporting structure, and the exact data for the candidate pad.
The loader manufacturer, lift plan and current CPS manufacturer specification remain the sources of truth. This guide is an early-screening aid.
Three sizing inputs plus the setup check
1. Maximum stabiliser reaction
Use the highest relevant vertical reaction for the exact loader, vehicle installation, stabiliser deployment, configuration and planned operation. Obtain it from the manufacturer information or the lift-planning method used by the competent person.
2. Assessed ground capacity
Use a permissible value for the actual support at each stabiliser location. “Concrete”, “tarmac”, “hardcore” or “grass” is a surface description—not proof of bearing capacity.
3. Exact pad specification
Check the manufacturer-listed dimensions, capacity, thickness and intended use for the exact product. Pad structural capacity and ground capacity are separate checks; passing one does not pass the other.
4. Real setup and contact
Confirm the foot fits, sits centrally and bears on a level, sound pad. Stiffness, support, damage and local bridging can make the effective area smaller than the geometric area.
How to calculate the minimum bearing area
This is the starting calculation, not a product approval. The area used must be the effective bearing area accepted by the lift plan or engineering method—not automatically the pad’s full outline.
Illustrative calculation—not a HIAB product recommendation
If the verified maximum stabiliser reaction is 80kN and the assessed permissible ground pressure is 200kN/m², the strict minimum area is 80 ÷ 200 = 0.40m².
The square root of 0.40 is approximately 0.632m, so the theoretical square bearing area would need sides of at least 632mm. The actual selection must then be checked for project factors, effective contact, the stabiliser-foot fit and the exact manufacturer-listed pad capacity.
Area calculated; selection still to verifyA practical selection workflow
Identify the exact loader and setup
Record the loader make and model, vehicle installation, stabiliser arrangement, planned radius, load and deployment mode. Do not size from the vehicle’s gross or kerb weight.
Obtain the governing reaction
Use manufacturer information or a competent lift-planning calculation. If the stabiliser force is unknown, stop the sizing exercise and obtain it.
Assess every support position
Check the surface, supporting layers, slopes, edges, recent excavation, services, covers, culverts, basements, voids and weather-related change.
Calculate the required area
Divide the maximum reaction by the assessed permissible ground pressure. Apply only the project factors required by the chosen method.
Verify the exact CPS candidate
Check current manufacturer data for dimensions, structural capacity and intended use. Confirm the foot can be centred and that the support can distribute the reaction effectively.
Set up, inspect and monitor
Use the loader in accordance with its instructions and lift plan. Inspect the pad and ground before loading, keep people clear of the stabilisers and monitor for movement or deterioration.
What common descriptions can—and cannot—tell you
| Information available | What it helps with | What it cannot prove |
|---|---|---|
| HIAB model or tonne-metre class | Identifies the loader family and lifting-moment context. | The maximum stabiliser reaction for the planned operation or the required pad area. |
| Ground described as concrete or tarmac | Flags the surface and possible damage considerations. | The slab thickness, supporting layers, hidden voids or permissible bearing pressure. |
| Pad length × width | Allows geometric area to be calculated. | That the entire outline is effective under the real support and loading conditions. |
| Manufacturer-listed pad capacity | Supports the separate structural product check. | That the ground or supporting structure can carry the imposed pressure. |
| A previous successful setup | Provides operational context worth recording. | That a different lift, location, weather condition or machine configuration is acceptable. |
Stabiliser deployment and site setup
Follow the loader manufacturer’s instructions and the lift plan. ALLMI’s site guidance treats full stabiliser deployment as the default and limits short rigging to machine-specific monitored systems or an arrangement authorised and controlled by the appointed person. A generic online guide cannot approve partial deployment.
Firm, level and stationary
Position the vehicle as level and stable as practicable, apply the vehicle and trailer brakes and use the stabilisers in accordance with the safe system of work.
Foot centred on the pad
Place the stabiliser foot centrally on a level pad. An eccentric or sloping setup increases local pressure and can compromise load distribution.
Hidden support hazards
Do not treat a strong-looking surface as a capacity certificate. Check covers, drains, services, basements, culverts, voids, made ground and recent excavation.
Stabiliser exclusion zone
Keep people clear during deployment and stowage, particularly around powered swing-up systems. Operators must understand the manufacturer’s controls and instructions.
What CPS needs to help narrow the range
For a useful commercial conversation—not a guess—send the following to sales@cranepadsolutionsuk.co.uk:
Machine and operation
Loader make and model, vehicle or installation details, planned load and radius, stabiliser configuration and the verified maximum reaction.
Ground and footprint
The assessed permissible ground or structural capacity, surface/support details, available footprint and any edges, services or access constraints.
Foot and handling
Stabiliser-foot dimensions, pad quantity, storage space, manual-handling limits and any requirement for handles, recesses or stowage.
Evidence
The relevant manufacturer or lift-plan extract and clear photographs of the setup area. Do not send customer or site information that is not needed for the enquiry.
Frequently asked questions
Is there a standard HIAB outrigger-pad size?
No universal size can be selected responsibly from the HIAB name or tonne-metre class alone. The reaction, ground capacity, setup and exact pad data must all be checked.
Can I choose a pad from loader tonnage?
No. Do not divide truck weight by the number of legs or infer a stabiliser force from a lifting-capacity label. Use the governing stabiliser reaction.
Do I need a pad on concrete?
The supporting slab or hardstanding still needs assessment. Its visible surface does not reveal thickness, support, damage, voids or load capacity.
Does a higher pad rating make the setup safe?
No. Pad structural capacity does not prove ground capacity, effective bearing area, correct centring or suitability of the lift.
Is a bigger pad always safer?
Not automatically. The pad must be strong and stiff enough, properly supported and correctly positioned. Some ground conditions or structures require specialist design.
Can the CPS calculator approve the lift?
No. It can screen entered values and help compare candidates, but it cannot establish the site capacity, replace manufacturer instructions or approve the lifting operation.
Primary guidance used for this review
The revised method follows lorry-loader and construction-plant guidance that separates stabiliser forces, ground capacity, pad area, strength, stiffness and competent planning.
Calculate, screen, then verify the exact setup
Bring the verified stabiliser reaction and assessed ground capacity. CPS can help narrow the product range, while the competent person retains control of the lift plan and final selection.
Screening limitation: This article and the CPS calculators do not approve a lift, confirm ground conditions or replace manufacturer instructions, a lift plan, competent ground assessment or project-specific engineering. If the stabiliser reaction, support capacity or exact pad data is uncertain, stop and obtain competent advice.
