An inspection opening is a purposely created or already existing opening in a structure, component, or tank that enables controlled access for examination, measurement, sampling, or internal work. In the practice of concrete demolition, strip-out, special demolition, and tunnel construction, it is a central element of structural diagnostics. When properly planned and executed, inspection openings can be produced with low vibration, dimensional accuracy, and safety—for example by selective nibbling with concrete demolition shears or by splitting with rock and concrete splitters powered by suitable hydraulic power units. This provides a clear, low-risk view into the construction and material, enabling well-founded preparation of subsequent steps.
Definition: What is meant by inspection opening
An inspection opening is an opening of defined size and location in concrete, masonry, natural stone, steel, or tank materials that serves the purpose of inspection, control, and processing either temporarily or permanently. It enables the exposure of reinforcement, voids, and utilities, the sampling of construction materials, the ventilation of enclosed spaces, as well as the insertion of measuring or working equipment. In existing structures, inspection openings are often created retrospectively; in new construction they can be provided structurally as access openings.
Tasks and application areas of inspection openings
The function of an inspection opening depends on the construction task and the material. In the application areas of Darda GmbH—concrete demolition and special demolition, strip-out and cutting, rock demolition and tunnel construction, natural stone quarrying, as well as special operations—inspection openings fulfill the following tasks in particular:
- Verification of reinforcement layout, component thickness, and concrete quality prior to deconstruction or strengthening works
- Localization and exposure of lines, inserts, or voids for damage diagnostics
- Pressure relief, ventilation, and safe accessibility in enclosed hollow bodies (e.g., vessels, tanks)
- Exposing joints and incipient cracks for controlled demolition without unwanted crack propagation
- Insertion of probes, endoscopes, suction, or flushing equipment for monitoring and sampling
- Enabling selective interventions during strip-out in sensitive environments with low emissions
Planning and preparation: location, size, and structural boundary conditions
Planning begins with a clear definition of the objective: What should become visible or accessible? From this, location, geometry, and the appropriate method are derived. For load-bearing components, structural boundary conditions must be taken into account; openings are positioned to preserve load-bearing zones and connections. Before starting, utilities must be located, the material buildup checked, and the work area secured. In sensitive areas, temporary shoring or redistribution of loads may be required. Approvals and protective measures are always project-specific and according to the applicable rules of the art.
Exploration and documentation
- Review as-built documents; combine locating and scanning methods
- Create trial cuts or small pilot openings for verification
- Organize protection against dust, noise, vibration, and falling objects
- Document dimensions, photos, and findings of the inspection opening in a traceable manner
Production methods in concrete, masonry, steel, and natural stone
The method is chosen according to material, environment, and objective. In many cases, hydraulic, low-vibration methods are appropriate because they work in a controlled manner and are gentle on the surroundings.
Selective nibbling with concrete demolition shears
Concrete demolition shears allow material-appropriate removal of small to medium segments, particularly during strip-out and concrete demolition. They are suitable for enlarging edge-adjacent openings step by step or revealing reinforcement without weakening the component uncontrollably. In combination with hydraulic power packs, this can be achieved with comparatively low emissions.
Splitting with rock and concrete splitters
Rock and concrete splitters—including dedicated rock splitting cylinders—generate a split in the material by controlled hydraulic pressure. In this way, dimensionally accurate inspection windows can be produced in thick components or natural stone with very low vibration and without sparking. The method promotes a clean, fracture-edged opening line and minimizes unwanted crack formation.
Cutting and separating steel and tank materials
For inspection openings in steel components, tanks, or pipelines, steel shears and tank cutters are used. They enable the clean cutting of plates and profiles. Multi cutters and combination shears combine cutting and pressing functions to open composite elements made of concrete and steel selectively, for example in composite structures.
Core drilling, sawing, and complementary methods
Core drilling, wire saws, or wall saws are common methods for circular or rectangular openings. They can be combined with hydraulic splitting or nibbling: drill holes define the contour, concrete demolition shears or splitters release the inner field. This combination is particularly suitable when edge quality and minimal peripheral damage are required.
Occupational safety, emissions, and environmental protection
Safety comes first. Measures depend on the material and environment. Hydraulically driven methods support low-emission work with reduced vibration and dust. For metallic vessels, safe emptying and ventilation are essential; where potentially hazardous media are present, appropriate clearance measurements and protection levels must be provided. Water flow and any resulting slurries must be collected in a controlled manner and disposed of properly. Accessibility, safe working platforms, and ergonomic handling of the tool must be planned in advance.
Quality criteria and post-treatment of the inspection opening
A properly executed inspection opening is clearly defined, easily accessible, and does not unnecessarily burden the remaining structure. After completion of the work, appropriate post-treatment follows.
Dimensional accuracy and edge quality
- Define and check geometry and tolerances on a project-specific basis
- Break or rework edges as required to reduce notch stresses
Reinforcement, cut edges, and temporary securing
- Protect exposed reinforcement against corrosion
- Deburr edges and cuts in steel components; for tanks, mitigate sharp edges
- Install temporary shoring or edging if required
Closure and reinstatement
- Close temporary openings with suitable systems (e.g., covers, mortar, plates)
- For permanent inspection openings, provide a secure and sealing execution
Practical sequence: step by step to the inspection opening
- Define the objective, review documentation, assess the environment
- Carry out locating, exploration, and pilot exposure
- Select the method: concrete demolition shear, rock and concrete splitter, cutting or drilling technology
- Secure the work area; define emission and protection concepts
- Create the opening: initially small, then expand to the specified dimensions
- Perform and document inspection, measurement, or sampling
- Rework edges, apply corrosion protection, and provide temporary securing
- Close or finish as an access opening—in line with purpose and specifications
Application-specific notes from practice
Concrete demolition and special demolition
Inspection openings serve the assessment of component thicknesses, the location of inserts, and the targeted separation of composite joints. Concrete demolition shears are suitable for creating openings step by step and exposing reinforcement without weakening large areas. Rock and concrete splitters help open thick components in a controlled manner and guide separation cracks precisely.
Strip-out and cutting
In strip-outs of existing buildings, low vibration, little dust, and controlled dimensions are crucial. Combination shears and multi cutters support the opening of composite members, for example where steel profiles connect to concrete elements. Hydraulic power packs enable finely metered, repeatable working in sensitive environments.
Rock demolition and tunnel construction
In rock and tunnels, inspection openings are used to check stratification, water ingress, or anchor positions. Rock splitting cylinders generate defined splits in natural rock to open small viewing windows—with minimal vibration and high control in confined situations.
Natural stone quarrying
Small inspection windows are helpful for assessing bedding joints, cracks, and block quality. Splitters enable controlled opening along natural planes of weakness without excessively damaging the block.
Special operations
In special situations—such as on tanks, pipes, or hard-to-reach components—tank cutters and steel shears create clean access points for inspection and recovery. Here, the combination of low spark formation, precise cutting guidance, and safe handling is decisive.
Tool spectrum and selection criteria
Various tool families are available for producing an inspection opening. Selection depends on material, environment, and objective.
- Concrete demolition shears: selective nibbling, good control, suitable for edge and corner areas
- Rock and concrete splitters as well as rock splitting cylinders: low vibration, for massive cross-sections and natural stone
- Combination shears and multi cutters: flexible for composite members, combining cutting and pressing functions
- Steel shears and tank cutters: metallic materials, profiles, and vessels
- Hydraulic power packs: energy-efficient, finely controllable drives for the full range of tools
Typical dimensions, tolerances, and clearances
Inspection openings are dimensioned to ensure the respective purpose is safely fulfilled. Common criteria include:
- Sufficient opening size for sight field, tool guidance, or sampling
- Minimum distances to edges, openings, and embedments to safeguard residual load-bearing capacity
- Edge quality and flatness for tight covers or subsequent closures
- Material- and component-dependent tolerances defined on a project-specific basis
Why low-vibration methods often offer advantages
Low-vibration methods such as splitting or selective nibbling have favorable effects on components, adjacent use, and measurement tasks. They reduce secondary damage, avoid uncontrolled crack formation, and improve occupational safety—especially in occupied buildings, existing stock, and sensitive facilities. Hydraulic drives support a precise, well-controllable execution.