Cable duct

A cable duct organizes, protects, and routes electrical conductors as well as data and control cables. In buildings, industrial plants, infrastructure structures, and especially in concrete construction, it creates clear routing paths, enables later accessibility, and reduces damage. For work in the application areas of concrete demolition and special deconstruction, strip-out and cutting, as well as rock excavation and tunnel construction, knowledge of the construction, location, and behavior of cable ducts is crucial to plan interventions safely, selectively, and with minimal damage. The connection to work reality becomes evident, for example, when controlled openings are made in concrete components along embedded ducts: here, the properties of the cable duct influence the selection of concrete pulverizers, rock and concrete splitters, and other hydraulic tools, while maintaining a product-neutral, professional approach. In specialist usage, cable ducts may also be referred to as trunking, raceways, or installation conduits depending on design and context.

Definition: What is meant by a cable duct?

A cable duct is a built-in or prefabricated system for orderly cable routing and for the mechanical protection of cables and conductors. This includes surface- and flush-mounted installation ducts, underfloor and floor ducts, ducts and conduits integrated in concrete, as well as tray-like solutions. Functions include routing, separation (e.g., power and data), shielding against external influences, fire protection measures through appropriate materials and firestopping, and ensuring maintainability and accessibility. Cable ducts are usually made of plastic or metal and have covers, dividers, fastening elements, and fittings for changes of direction and branches. In practice, additional criteria such as ingress protection, impact resistance, smoke and toxicity behavior of plastics, and electromagnetic compatibility are considered to align with project-specific risk assessments and applicable codes.

Construction, types, and materials of cable ducts

Cable ducts differ by location, material, and purpose. What is essential is how they react to mechanical loads, heat, moisture, and chemical influences, and how they behave during deconstruction. The choice affects service life, safety, and later processing during demolition and conversion phases. Environmental exposure classes – interior dry areas, wet rooms, outdoor with UV, or embedment in concrete – determine the required material properties and joints.

Distinction by location: surface-mounted, flush-mounted, and in concrete

Surface-mounted ducts run visibly on walls or ceilings. They are easily accessible and often modular. Flush-mounted ducts and chases disappear behind plaster or cladding; the route layout depends on documentation and is difficult to locate if as-built information is lacking. Ducts and conduits integrated in concrete are placed during formwork or worked in afterward. For work with concrete pulverizers and rock and concrete splitters, the position relative to reinforcement, anchors, and embedded components is essential to open precisely and with low vibration. Where documentation is incomplete, non-destructive locating and cautious trial openings minimize collateral damage.

Underfloor and floor ducts

Underfloor systems run within screed or subfloor. They supply workstations, machines, or switchgear. Covers, inspection openings, and boxes allow access. During strip-out and cutting, these sections are selectively exposed before load-bearing components are processed. Load classes for floor boxes, resistance to moisture ingress, and clean separability of power and data spaces are central to planning and later dismantling.

Materials and components

• Plastic ducts (e.g., halogen-free) with covers and dividers for power and data cables
• Metal ducts made of steel or aluminum with increased impact resistance and temperature resistance
• Insert ducts, installation conduits, and boxes for concrete construction
• Fasteners, hangers, and penetrations with appropriate sealing and firestop elements

In addition, fittings and accessories such as reducers, bends with compliant radii, strain relief elements, and identification systems ensure functional continuity and safe maintenance. Material selection should reflect thermal loads, expected electromagnetic fields, and corrosion potential in the given environment.

Planning, sizing, and route layout

A proper route considers cross-section, permissible fill factor, reserve for future additions, bend radii, separation of different systems, and accessibility for operation and maintenance. Transitions between duct types, for example from flush-mounted to underfloor, must be mechanically and from a fire protection standpoint consistent. In massive components, reinforcement layers, concrete cover, minimum clearances, and component constraints must be observed. Typical planning values include a fill factor aligned with manufacturer guidance and codes, thermal derating for tightly packed conductors, and defined separation distances for EMC-sensitive lines.

1. Record the cable inventory and performance data (voltages, cross-sections, communication requirements)
2. Define the route: shortest possible, service-friendly paths with clear reference points
3. Sizing and separation: sensibly segregate power, control, and data
4. Define transitions across components, penetrations, and inspection points
5. Create documentation and maintain it for future modifications
6. Coordinate with other trades and digital models to prevent clashes and ensure maintainability
7. Define test, acceptance, and labeling standards for handover and later changes

Cable ducts in existing structures: investigation, locating, and documentation

In existing buildings, plans are often incomplete. Before interventions, routes are reviewed, marked, and-if necessary-investigated using non-destructive methods. These include visual inspection, tactile tracing, endoscopy via existing openings, cable locating, and cautious exposure of individual sections. The results flow into updated as-built documentation. This is the basis for targeted progress within strip-out and cutting and during concrete demolition.

Complementary techniques such as ground-penetrating radar, rebar scanning, and electromagnetic locating refine the picture of embedment depth and proximity to reinforcement. Findings are consolidated in a traceable log with photo evidence and coordinates to support selective opening and later reinstallation where required.

Deconstruction and opening of cable ducts in concrete

For selective deconstruction, cables must be identified, isolated, tested, and dismantled before massive members are processed. Embedded ducts, conduits, and boxes influence the fracture behavior of the concrete. Precise, stepwise openings along the duct axis facilitate low-damage recovery and reduce secondary damage to adjacent structures. Dust, vibration, and noise emissions are minimized by choosing suitable sequences and tools, and by applying extraction and shielding measures.

Selective intervention with concrete pulverizers

Concrete pulverizers enable controlled nibbling of concrete webs, exposing ducts in wall or ceiling areas, and separating local edges, for example at inspection openings. The combination of high shear force and limited removal width allows ducts to be made accessible section by section. Steel reinforcement becomes visible and can then be cut in the next step with suitable cutting tools. Adjusting jaw pressure and working in small bites reduces spalling and preserves adjacent components.

Controlled splitting with rock and concrete splitters

Rock and concrete splitters act with high, locally introduced forces. They are suitable for exposing ducts in massive components without impact and vibration loads. By using drilling patterns adapted to the component and the correct sequence of setting, separation cracks form where they are planned – e.g., along the duct axis or between the duct and the adjacent reinforcement zone. This protects the surroundings and embedded items and improves the recyclability of separated parts.

Hydraulic system chain and tool changeover

For changing work steps-opening, splitting, cutting-hydraulically driven tools are coupled to suitable hydraulic power packs. This enables efficient changeover from a concrete pulverizer to a rock splitting cylinder or to steel shears and multi cutters. Selection is based on member thickness, reinforcement ratio, embedded parts, and the material of the cable duct (plastic, sheet steel, aluminum). Quick couplers, pressure and flow matching, and oil cleanliness management support consistent performance and reduce downtime.

Occupational safety and electrical safety

Before working on cable ducts, ensure safe isolation from the power supply, mark the work area, and test for absence of voltage. Mechanical risks (pinch, crush, cut injuries), dust generation, and noise must be minimized with appropriate measures. In areas with elevated fire load or in confined spaces, plan for extinguishing agents, ventilation, and escape routes. When working on embedded routes, clear communication channels between electrical specialists and deconstruction teams take priority. Lockout-tagout procedures, suitable measurement devices, and defined re-energization protocols are part of the documented safety concept.

• Isolate and secure against re-energization
• Test and document absence of voltage
• Mark the route; define protection zones
• Minimize dust and sparks; provide extraction
• Use personal protective equipment and maintain safety distances
• Coordinate hot work permits and gas monitoring where required

Fire protection, firestopping, and building requirements

Cable ducts often penetrate elements forming fire or smoke compartments. Accordingly, firestopping, sealing systems, and material selection must be matched to the required protection. During deconstruction, these elements are documented, separated by material type, and-if part of a reconfiguration-replaced with equivalent solutions. During careful opening, for example with concrete pulverizers, the integrity of adjacent fire-protection-relevant components should be preserved. In underfloor areas, tight cover systems prevent the spread of smoke and hot gases; such functions must be restored after interventions.

Where penetrations are reinstated, performance class, installation details, and identification are recorded to maintain traceability. Smoke tightness, durability under movement, and compatibility with cable sheath materials are verified during acceptance.

Material separation, disposal, and circular economy

During removal, plastics, metals, sheathed cables, and concrete debris are generated. Separate collection facilitates recycling and reduces disposal costs. Low-vibration methods, such as the use of rock and concrete splitters, reduce secondary damage and keep material fractions in better quality. Metal duct parts can be efficiently downsized with steel shears or multi cutters; plastics are collected by type. Cables are treated separately where intended. Hydraulic methods support precise dismantling with lower dust and noise.

Documentation of quantities and fractions supports compliance and potential reuse. Halogen-free plastics and aluminum often exhibit favorable recycling routes, whereas mixed or contaminated fractions require proper conditioning. Clean cutting and low dust loads improve recyclate quality.

Cable ducts in tunnel structures and in rock excavation

In tunnels, cable ducts run along the walls, at the roadway edges, or in niches. They carry power, control, communications, and safety-critical systems. During modification or expansion, low vibrations and controlled interventions are crucial to protect operations and infrastructure. Rock and concrete splitters are suitable for targeted openings in massive cover slabs and edge beams. Metal inserts, covers, and brackets can be separated with steel shears or combination shears. Where cutting torches are required, special safety measures must be observed; use depends on material, wall thickness, and accessibility.

Operational constraints such as evacuation routes, ventilation effects, and signaling interlocks are factored into work sequencing. Robust shielding and clear zoning ensure that adjacent equipment remains protected and accessible.

Typical damage and its assessment

In service, wear and damage occur: deformed covers, corroded metal ducts, embrittled seals, ducts integrated in concrete with cracking in adjacent zones. Causes include overload, moisture, temperature changes, improper fastening, or crushing. Before deconstruction, a condition assessment focusing on load-bearing components, proximity to reinforcement, corrosion indicators, and media separation helps. This influences the choice of opening method: localized nibbling with concrete pulverizers, linear splitting, or cutting covers and brackets with multi cutters.

Evidence-based assessment includes photographic records, measurements of corrosion loss, checks of fastening integrity, and verification of functional separation between power and data. Findings inform both the deconstruction approach and any temporary safeguarding measures.

Practice in the application areas

• Concrete demolition and special demolition: Embedded ducts are exposed locally, cables are dismantled, and then components are removed with concrete pulverizers or separated with rock and concrete splitters. Neighboring components largely remain intact.
• Strip-out and cutting: Surface- and flush-mounted ducts can be systematically removed. Underfloor systems are opened, cleaned, and dismantled by material type before cut- or drill-intensive work begins.
• Rock excavation and tunnel construction: Cable routes in niches and edge areas require low-vibration methods. Splitters and precise cutting tools act in a controlled manner, even with limited accessibility.
• Natural stone extraction: Temporary cable routes for power and control must be protected against mechanical loads. Robust, quickly installed duct or tray solutions facilitate safe operation and subsequent dismantling.
• Special operations: In complex facilities with sensitive equipment, selective opening along documented routes is essential. Hydraulic tools with fine metering support controlled work steps.

Across all areas, a consistent sequence of locate-expose-separate, combined with clear documentation and acceptance criteria, reduces rework and safeguards interfaces with other trades.

Workflow: from investigation to acceptance

1. Survey the existing situation: review plans, locate routes, assess risks
2. Establish electrical safety: isolate, secure, test
3. Dismantle the cables: label, disconnect, sort
4. Opening the components: localized with concrete pulverizers, linear with rock and concrete splitters, metal parts with steel shears or multi cutters
5. Material separation and disposal: collect by type, transport, document
6. Quality assurance: visual inspection, dimensional checks, restoration of required building functions
7. Final documentation and acceptance: update as-built records, verify firestopping, and confirm maintainability

Good practice for selecting and using tools

The choice of tools depends on member thickness, reinforcement content, duct material, and the surroundings. Hydraulic power packs provide the necessary output, while concrete pulverizers and rock splitting cylinders enable controlled opening. Metallic covers, support rails, and brackets are separated with steel shears or combination shears. In tight interior spaces and sensitive environments, low-vibration methods support occupational safety and protection of the building fabric. A clear sequence-locate, expose, separate-increases precision and reduces rework.

• Match tool capacity to section thickness and reinforcement ratio; test on a non-critical area first
• Use drilling patterns tailored to the desired crack path for splitting operations
• Maintain sharp cutting edges and calibrated hydraulic pressures to ensure predictable behavior
• Provide extraction and shielding near openings to protect adjacent installations and improve visibility