Floor loading and ground bearing pressure: industrial floors, slabs and paving

In short: the floor does not “feel” the machine’s weight spread over the area it occupies. It feels the wheel load or outrigger-pad load and the ground bearing pressure at that point. JLG specification sheets give the maximum ground bearing pressure (in kg/cm² or daN/cm²) and many manuals also list the maximum load per wheel. Before working on suspended slabs, in shopping centres, in underground car parks or on paving, ask the structural engineer or the building manager for the allowable load — both the uniformly distributed load and the concentrated load — and add the platform load to the weight of the machine.

Indoors, in shopping centres and in buildings, the risk is not only whether the platform is stable: it is also what the floor can take. A compact scissor lift of a little over one and a half tonnes can put, under each tyre, a pressure many times higher than the uniformly distributed load the slab was designed for. This guide explains the difference between wheel load and ground bearing pressure, where that matters, how to find the right figures in JLG publications, and what to check on the route and at the work position.

Wheel load and ground bearing pressure are not the same thing

Three quantities are easy to confuse and should be read separately:

• Weight of the machine (and the load in the platform). This is the total mass: the machine, people, tools and materials in the platform. JLG specification sheets publish the machine weight and note that certain options or country standards increase it. In use, always add the platform load.
• Wheel load or pad load (concentrated load). This is the force that goes through a single tyre, track or outrigger pad. It is not shared equally by all four wheels: with the scissor or boom extended, or with the platform deck extension out, one wheel can take a much larger share of the weight. IPAF calls this a point load — a force applied at a concentrated point.
• Ground bearing pressure (contact pressure). This is that force divided by the contact area of the tyre, track or pad. The smaller the area, the higher the pressure, even at the same weight. JLG’s EMEA specification sheets usually give it as maximum ground bearing pressure, in kg/cm² or daN/cm².

A useful way to see the difference: if you divide the total weight by the machine’s plan area (length × width), you get a relatively low “average” pressure. The floor, however, is not loaded over that whole area: it is loaded only under the wheels or pads. In its Floor Loading Specs (ANSI A92.20), JLG distinguishes occupied floor pressure (the average pressure over the occupied area) from maximum tire ground bearing pressure (the maximum pressure under one tyre, with the machine in its working configuration and supporting its rated load) and from maximum tire load (the maximum load on one wheel).

Many building slabs and floors are specified with a uniformly distributed load (for example in kN/m²) and, separately, with an allowable concentrated load (in kN, over a given area). An aerial work platform behaves as a concentrated load, not as a uniformly distributed one. Comparing only the machine’s weight with the floor’s distributed load is not enough and can be misleading.

Units: kg/cm², daN/cm² and kPa

On JLG sheets for Europe, kg/cm² is common. 1 kg/cm² is about 98 kPa (almost 100 kN/m²). On the X-series crawler booms, JLG uses daN/cm²: 1 daN/cm² is exactly 100 kPa, or about 1.02 kg/cm². Values in psi in ANSI publications convert in the same way (1 psi ≈ 0.0703 kg/cm²). What matters is to compare like with like: pressure with allowable pressure, wheel load with allowable concentrated load.

Why this matters on industrial floors, slabs and paving

A well-built industrial ground-bearing slab is usually more tolerant than a suspended slab. Even so, joints, drains, manhole covers, defects in the concrete and finishes (epoxy resin, tiles, paint) can suffer when the machine travels or works. IPAF notes that many floors, basements and intermediate slabs cannot support the weight of a MEWP and could collapse without warning.

• Suspended slabs and mezzanine or raised floors. IPAF recommends operating on a suspended floor only when it has been shown that the surface can safely support the MEWP in all positions with the maximum allowable load in the platform. Ask the person in control of the site for the loading limits and, in these cases, for the view of a structural engineer. A newly cast slab or a hollow-core floor only reaches its design capacity once the intended work (grouting, reinforced screed and so on) is complete and has cured.
• Shopping centres and occupied buildings. These are almost always suspended slabs, with visible finishes and public circulation. Besides the structure, there is the risk of marking or crushing the floor, overloading joints, and working next to openings, stairs and plant rooms.
• Raised floors and light mezzanines. Many were never designed for aerial work platforms. Do not assume they can take the machine just because the floor “looks solid”.
• Tiled, stone or epoxy floors. Even if the structure can take the load, the finish can crack, chip or stain. Non-marking tyres, protective mats and spreader plates reduce the risk of surface damage.
• Portuguese cobblestone (calçada portuguesa) and sidewalks. Calçada is typically small stones on a bedding layer. A concentrated wheel or pad load can settle, shift or break stones, especially at edges, in poorly bedded areas or where the surface is already uneven. The same applies to sidewalks, kerbs and pedestrian paving that “look firm” but were not designed for this kind of load.
• Underground car-park slabs. These are suspended slabs, often with drainage channels, joints, ramps and limited headroom. IPAF specifically highlights multi-level car parks and shopping centres: ask for the loading limits and do not conclude that the slab can take the machine just because a light vehicle has already used it.

IPAF also makes a practical point: travel loads and working loads are not the same. Just because the machine has driven across an area does not mean that area can safely support the MEWP in operation — for example with the scissor raised, with the deck extension out, or, on a boom, with the boom slewed over one wheel. Pressure spreads down and outwards in a fan below the point of contact, so the area around the contact point also matters.

How to get the figures: JLG specification sheets and manuals

The right figures are those of your machine: the data plate, the operation and safety manual, and the specification sheet for that model and version. JLG publishes the weight and the maximum ground bearing pressure on its specification sheets; maximum wheel load may also appear in manuals and in the Floor Loading Specs. During the pre-use check, confirm the data plate and the condition of the floor using the electric scissor lift checklist. JLG manuals are organised by model.

The examples below are figures published by JLG on EMEA specification sheets. They illustrate the order of magnitude and the differences between machine types — they do not replace the sheet and manual of the unit you will use. Options, country standards and the year of manufacture can change the weight and the pressure.

The table makes the main point: the ES1932 weighs 1,565 kg and reaches 8.01 kg/cm² under the tyres; the ERT2669, which is heavier (3,677 kg), stays at 2.75 kg/cm² thanks to much larger tyres; the Toucan 10E, at 2,980 kg, reaches 21.5 kg/cm² — a clearly higher pressure, because the contact area is smaller and the load concentrates when the mast and jib are at work. A “lighter” machine or a compact mast lift is not automatically gentler on the floor. The X17JP and X20JP crawler booms show the other side: when travelling on their tracks, pressure falls to about 0.64 to 0.67 daN/cm²; when working on the outriggers it rises to 2.45 and 3.04 daN/cm², still well below compact scissor lifts with narrow solid tyres. The X20JP outrigger footprint is 2.92 × 2.92 m (centre of the pads).

Spreader pads, non-marking tyres and floor protection

IPAF recommends that spreader pads should be used with all MEWPs that have outriggers, unless a risk assessment shows they are not necessary; they should always be used with boom-type MEWPs when the machine is fully supported on its outriggers. Even when pads are supplied with the machine, a larger pad may still be needed for that floor. The type, size and thickness are for the person planning the work to decide, after assessing the ground or floor. IPAF provides a spreader pad calculator as guidance for boom machines supported on their outriggers, to be used only after the supporting surface has been assessed.

• Spreader plates and protective mats. They must be stiff enough not to dish and to spread the load over the whole area of the pad. Pads are made in engineering plastic, aluminium, steel or timber; if timber is used, it must be dry, in good condition and of adequate thickness (IPAF advises against scaffold boards). On delicate floors, use mats or protective paths along the route as well, not only at the work position.
• Pads centred. The outrigger foot should sit in the middle of the pad, and the pad should bear evenly on the floor. IPAF recommends checking this periodically during the work.
• Non-marking tyres and tracks. On indoor electric scissor and mast lifts, non-marking solid tyres are the usual way to avoid marks on light or resin floors. On JLG X-series crawler booms, non-marking pads and low-profile non-marking tracks are standard features on the EMEA specification sheets.
• What pads cannot do. They spread the load at the finish and reduce contact pressure; they do not increase the structural capacity of a slab that is already at its limit. If the slab does not have enough allowable concentrated load, change the machine or the position, or obtain a structural opinion — do not “fix” it with a thicker mat alone.

Ask the structural engineer or the building manager for the limits

The person in control of the site should give the allowable floor load on the route and at the work position: the uniformly distributed load and the concentrated load, with the intended area of application. On suspended floors, IPAF treats this planning as different from an open construction site and notes that a structural engineer may be needed. Trapézio de Prismas does not carry out that structural calculation: we help you choose the machine and read the figures in the specification sheets and the manual, but whether the floor is adequate is the responsibility of those who manage the building and, where required, of the building’s engineer.

Take to that discussion the model and serial number, the machine weight, the planned platform load, the maximum ground bearing pressure and, if it is in the manual, the maximum load per wheel or pad. Also say how many machines may be working in the same area.

Plan the route, not only the work position

IPAF recommends that the operator should walk the route the machine will take and that, if there is any doubt about the floor in any configuration, the machine should not be used. Check:

• Ramps and slopes, within the machine’s gradeability and with a dry surface that gives traction.
• Lifts and goods lifts: capacity, dimensions and protection of the car floor. The weight to use is the machine plus its load, not only the brochure weight.
• Expansion joints, drains, gratings and manhole covers. These are weak points for concentrated loads; do not park or raise the platform on them.
• Openings, doorways and areas under construction, where the slab may have less support.
• Headroom, especially in underground car parks and basements.
• Floor protection along the whole route, not only under the machine at the work position.

The right weight, and alternatives that suit the floor

The figure to compare with the floor is the weight of the machine plus the load in the platform (people, tools and materials), in the configurations in which you will travel and work. If the specification sheet says that options increase the weight, use the real weight of the unit, not the lowest catalogue figure.

When the floor is the limiting factor, there are alternatives — but choose them by pressure and concentrated load, not by weight alone:

• Compact electric scissor lifts, such as the ES1932 or the ES2632, fit through doorways and corridors and are the usual choice indoors. Even so, the pressure under their narrow solid tyres is relatively high: 8.01 and 7.52 kg/cm² in these two examples. See how to choose a JLG scissor lift.
• Mast booms, such as the Toucan 10E, are useful in aisles and for reaching over obstacles. The weight may be moderate, but the contact pressure can be higher than that of a scissor lift: 21.5 kg/cm² on this model. Compare an electric scissor and a mast boom with the floor in mind as well.
• Crawler booms (X series), such as the X17JP and the X20JP, travel on tracks at low pressure and work on outriggers, with pads and, when the floor requires it, spreader plates and mats. They are an option when you need more height or must pass through a narrow opening, always with the floor assessed. See when to use a crawler boom.
• Push-around and low-level access lifts, when the working height allows, clearly reduce the weight and the concentrated load.

A practical checklist before you take the machine inside

1. Identify the type of floor on the route and at the work position (ground-bearing slab, suspended slab, mezzanine, resin, tiles, cobblestone paving, underground car park).
2. Ask the building manager, and a structural engineer where appropriate, for the allowable loads: uniformly distributed and concentrated.
3. Note the model and serial number, the real weight of the machine, the planned platform load and the maximum ground bearing pressure (and the load per wheel or pad, if it is in the manual).
4. Compare those figures with the floor limits in all configurations: travel and work, with the deck extension or boom in the intended position.
5. Walk the route: ramps, lifts, joints, drains, covers, openings, headroom and areas with a delicate finish.
6. Prepare suitable tyres or tracks, protective mats and, on machines with outriggers, spreader pads of the right size and stiffness, with the foot centred on the pad.
7. Do not park or raise the platform on joints, gratings, manhole covers or the edges of paving.
8. If the floor’s capacity has not been confirmed, do not go ahead: change the machine or the position, or wait for a structural opinion.

Need help choosing the right machine?

We are the official JLG dealer in Portugal. We help you choose the right platform for work indoors, in shopping centres and in buildings, whether you need new JLG machines or aerial work platform rental. You can check the JLG manuals to confirm the weight and ground bearing pressure of your machine. We do not carry out the building’s structural calculation; that opinion belongs to the engineer or to the person responsible for the floor.

If you would like help choosing a machine or a technical inspection, contact us.