Outrigger Pads for Boom Trucks: Sizing and Setup Guide

07 October, 2026 | Admin

SafeRig outrigger pad — Barq Al Mustaqbal Contracting Company case study

Short answer: boom trucks and truck-mounted cranes work from outriggers on roadsides, yards and building sites, often on ground nobody has tested. Size your outrigger pads for a boom truck from the leg load in the manufacturer’s chart, then use the ground-pressure formula. Do not set up on bare outrigger floats.

Table of Contents

Why Boom Trucks Need Extra Care

They stop wherever the job is: kerbs, asphalt edges, fill and near trenches.
Outriggers often have a shorter span than on large mobile cranes, so the load per leg is high.
Set-up is frequent, so the pads get handled all day. Weight and durability matter.

Sizing Steps

Get the maximum outrigger reaction from the load chart, in tonnes.
Choose the ground category. Treat unknown ground as sandy or weaker.
Compute minimum area = leg load × 9.81 × safety factor ÷ allowable pressure.
Pick the smallest standard pad with area above the minimum and rated capacity above the leg load.

Reference allowable pressures used in this guide:

Ground	Indicative allowable pressure
Rock or compacted aggregate	300 kPa
Compacted fill	200 kPa
Sandy ground	120 kPa
Sabkha, soft or reclaimed	75 kPa

Worked Example (Planning Estimate)

A boom truck weighs 18 tonnes and lifts 5 tonnes, a total of 23 tonnes. With no load chart figure to hand, use the 60% planning assumption: 23 × 0.60 = 13.8 tonnes on the worst leg. The ground is compacted fill (200 kPa) and the safety factor is 1.5.

Leg load: 13.8 × 9.81 = 135.4 kN
Factored: 135.4 × 1.5 = 203.1 kN
Minimum area: 203.1 ÷ 200 = 1.02 m²
The 1000 × 1000 mm pads (1.00 m²) miss by a hair. The smallest standard pad that passes is 1200 × 1200 mm (1.44 m²), for example SR-12126 (1200 × 1200 × 60 mm, rated capacity 180 tonnes).

Replace the 60% assumption with the real leg load before the lift. For the full method and a free Excel template, see Crane Outrigger Load Calculation.

Setup Checklist

Level the ground under each pad and remove loose material.
Centre the outrigger float on the pad.
Keep pads clear of trench edges, drains, manholes and buried services.
Use the same pad size under all four outriggers unless the load chart says otherwise.
Re-check after rain or any sign of settlement.
Inspect pads for cracks, deep gouges or warping between jobs.

Common Boom Truck Mistakes

Setting outriggers on kerb edges or the shoulder of an asphalt road, where the edge can break away.
Using small pads sized for a pickup-mounted crane under a heavier truck crane.
Stacking several small pads instead of using one correctly sized pad.
Placing a pad over a drain cover or a recently backfilled trench.

Which Material?

For a boom truck that moves between jobs daily, a light UHMWPE pad is easier to carry and position than timber or steel. See Outrigger Pads vs Timber Cribbing and our range of Saferig outrigger pads.

Frequently Asked Questions

What size outrigger pad does a boom truck need?

It depends on the leg load and the ground. Use the formula in this guide or our free Outrigger Pad Size Calculator.

Can I use timber under a boom truck?

For a one-off job, it can be acceptable. For repeat use in hot climates, timber degrades faster and costs more over time.

Do boom trucks need pads on asphalt?

Yes. Asphalt softens in heat and the load concentration can punch through or deform it. A pad spreads the load.

Can I use one pad size for every job?

Only if it passes the area and capacity checks for your heaviest lift on your weakest likely ground. Otherwise size per job.

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