Surface load is a central topic wherever components, floors, and subgrades must be safely loaded. In concrete demolition, special demolition, strip-out, as well as in natural stone extraction and tunnel construction, the correct assessment of surface load determines whether equipment, material storage, and demolition debris rest safely and whether components are not overstressed in their load-bearing capacity. Especially for work with concrete demolition shears, hydraulic rock and concrete splitters, and compact hydraulic power units, controlled load distribution on slabs, floor slabs, or rock bearings is an essential part of safe and efficient work planning.
Definition: What is meant by surface load
Surface load refers to the force per unit area acting on a subgrade or a structural element. In practice, it is usually given in kilonewtons per square meter (kN/m²). Mathematically, it is defined as q = F/A, i.e., the quotient of applied force F and loaded area A. Surface loads can be uniformly distributed or non-uniform; surface loads frequently result from point loads (e.g., equipment feet) or line loads (e.g., edge bearings) redistributed via auxiliary means. Distinct from surface load is surface pressure or contact stress at immediate contact surfaces, for example under skids or plates. For practical deconstruction work, both quantities are relevant because they influence load-bearing capacity, cracking, and deformations.
Importance of surface load on construction sites and in deconstruction
In demolition and deconstruction scenarios, several load components coincide: the self-weight of components and equipment, live loads from attached tools, temporary storage of demolition debris, and dynamic portions from work processes. Concrete demolition shears, for example, generate alternating loads by gripping, crushing, and breaking; stone and concrete splitters generate high, locally introduced forces that must be carried into floors or slabs via bearing surfaces. A sufficient bearing area and targeted load distribution then determine whether the resulting surface loads remain within the allowable values of the load-bearing structure.
Surface load in concrete demolition and special demolition
When processing reinforced concrete components with concrete demolition shears or combination shears, loads from the tool, carrier machine, hydraulic power pack, and material accumulation act together. These summed forces are distributed via wheels, tracks, supports, or auxiliary bearings onto the floor or slab surface. The smaller the bearing area, the larger the resulting surface load. Therefore, in storey-by-storey deconstruction, load distribution plates, timber beams, or steel sheets are often used to convert point loads into surface load and thus comply with the slab load-bearing capacity.
Typical influencing factors
- Self-weights: tools (e.g., concrete demolition shears), hydraulic power packs, supply lines
- Live loads: operating personnel, component add-ons, temporary storage of demolition debris
- Dynamic components: impact and vibration loads from cutting and splitting operations
- Contact geometry: tires, tracks, supports, plates and their contact area
- Component condition: crack pattern, deflection, bearing, and cross-section weakening
Calculation and conversion in practice
The basis is the relation q = F/A. From masses, forces are obtained using F ≈ m · g (with g approx. 9.81 m/s²). Several loads add up to a total load that is transferred via a real or enlarged contact area. From line loads (e.g., rails) or point loads (e.g., supports), surface loads can be generated using auxiliary means (plates, timber beams). For practical assessment, compare with the allowable surface loads of the component; these vary depending on design, construction age, condition, and use. Reference values can vary widely; decisive are project-specific documents and a technical assessment.
Simple calculation example
A tool with a total mass of 1,200 kg (including hydraulic power pack and adapters) generates a weight force of around 11.8 kN. If the effective bearing area is 0.25 m², the resulting surface load is about 47 kN/m². If the bearing area is increased by load distribution plates to 1.0 m², the surface load drops to around 11.8 kN/m².
Load distribution and bearing areas
Targeted load distribution is the most effective lever for reducing surface load peaks. When working with stone and concrete splitters or concrete demolition shears, load distribution plates, multilayer timber beams in crosswise arrangement, and robust steel sheets reduce surface pressure and redirect loads into load-bearing areas.
Proven measures
- Load distribution plates made of steel or hardwood to enlarge the bearing area
- Crosswise stacking of timber beams to minimize point loads
- Shimming to achieve full-surface bearing without tipping edges
- Interlayers (rubber/PU) to damp dynamic peaks, where suitable
- Plan load paths to direct loads onto load-bearing walls, beams, or columns
Surface load in strip-out and cutting
In concrete cutting, core drilling, or separating with multi cutters, loads arise from machine weight, contact forces, and the build-up of stacks of cut material. Particularly on upper floors, cut material and demolition pieces must not be stored uncontrolled. The combination of limited surface load and local surface pressure at rollers and feet requires careful planning of work sections, removal, and temporary storage.
Practical notes
- Keep sections small; remove cut material promptly
- Use equipment with wide skids/supports or additional plates
- Consider wet substrates and slurry (friction, slip hazard, bearing quality)
Rock demolition, tunnel construction, and natural stone extraction
Rock splitting cylinders and Rock Splitters generate high splitting forces in rock, while reaction forces are introduced into the ground via the bearing. On rock benches, surface pressure is often less critical than on loose soils; nevertheless, local pressure peaks must be avoided to prevent spalls or edge break-offs. In tunnel areas, bearing width, subgrade strength, and moisture influence the secure footing of power packs and equipment.
Subgrade assessment
- Solid rock: high contact stresses possible; consider edge break-offs
- Concrete bases: check load-bearing capacity; monitor existing cracks and deflections
- Asphalt/gravel: allow for settlements; provide large-area bearing
- Fills: low and highly variable capacity; minimize loads
Tool selection and surface load
The choice of suitable tool indirectly influences surface loads. Concrete demolition shears enable targeted removal with reduced impact peaks compared with percussive methods, which can reduce the need for extreme load reserves. Stone and concrete splitters introduce high forces locally; here, bearing areas and reaction forces require special attention. Steel shears and tank cutters often lead to lower component reactions in concrete; however, workpiece weights and handling can govern the surface load on the work floor. Hydraulic power packs control power delivery but increase total load as additional mass and should therefore always be included in the surface load assessment.
Planning steps for a safe surface load assessment
- Survey existing conditions: element type, spans, supports, visible damage, deflection
- Determine loads: self-weights of tools (e.g., concrete demolition shears), carrier machine, hydraulic power packs, demolition debris, personnel, and auxiliaries
- Determine contact areas: actual bearing areas, supports, skids, plates
- Calculate surface loads: divide load sums by bearing area; account for dynamic components
- Compare with allowable values: use capacity verifications from design documents or competent assessment
- Plan load distribution: plates, timber beams, shoring, load paths to load-bearing elements
- Define sequence: sections, order, minimize temporary storage, ensure removal logistics
- Monitoring: observe deflections, cracks, noises, and settlements; implement measures if anomalies occur
Terminological distinctions in technical practice
In practice, surface load is often equated with surface pressure. Technically, surface load is the distributed loading of an element (e.g., slab in kN/m²), while surface pressure describes the contact stress at the immediate bearing (e.g., under a support). Both quantities are relevant: a slab can carry a certain surface load, while local surface pressures under a support can still lead to spalling. Equally important is the distinction to line load (kN/m) and point load (kN), from which a distributed surface load can be generated via auxiliary means.
Avoid typical planning errors
- Temporary storage of heavy demolition debris without considering surface load
- Underestimating dynamic load peaks when using concrete demolition shears or combination shears
- Load distribution plates that are too small or compliant, which embed and reduce the effective area
- Unfavorable load paths away from load-bearing walls, beams, or columns
- Lack of monitoring of deflections and crack patterns during execution
Legal and safety guidance
The determination of allowable surface loads and the assessment of load-bearing capacities are fundamentally based on the applicable rules of construction and project-specific verifications. Information on load capacities must always be interpreted specific to the object. In case of uncertainties, expert assessments are required. For operations, protective measures against sliding, tipping, and local overstressing must be taken; the work area must be organized so that load changes remain controllable.
Monitoring and documentation
Ongoing control of deformations and bearing conditions increases safety. Practical measures include markings of crack widths, measuring wedges at joints, controlled settlement indicators under load distribution plates, and regular visual inspections. Simple documentation of equipment positions, load distribution aids, and material storage supports traceability and adjustment of the approach.
Practical application examples
Slab dismantling on an upper floor
For work with a concrete demolition shear, the total load from the tool, carrier machine, and hydraulic power pack, including a working margin, is determined. Using large-area steel plates under the supports quadruples the contact area, lowering the surface load below the allowable slab criteria. Demolition debris is removed section by section to avoid additional surface loads.
Rock processing with rock splitting cylinders
The reaction forces from the splitting process are introduced via wide, rough bearings into the rock. Edges are protected by shimming to avoid local overpressures. Loosening or undermining of the subgrade is eliminated before the full load is applied.
Material and subgrade influence on surface load
The load-bearing capacity of the bearing area strongly depends on the material. Reinforced concrete slabs carry high uniformly distributed surface loads but are susceptible to local surface pressures at edges and cracks. Masonry vaults react sensitively to concentrated bearings. Asphalt and gravel deform and reduce the effective contact area when plates sink. Wet or contaminated subgrades change friction values and can impair stability. These factors must be considered when selecting concrete demolition shears, stone and concrete splitters, and their bearing aids.
Good practice in load planning
- Capture total loads completely, including accessories and auxiliaries
- Check surface loads at the most unfavorable locations (e.g., edges, openings)
- Define load distribution early using suitable plates and timbers
- Choose the work sequence so that load peaks occur at different times
- Continuous control and adaptation when boundary conditions change