The term threshold stone refers in the construction and infrastructure context to different yet functionally related elements: on the one hand, the door or floor threshold made of natural stone or concrete in buildings; on the other, the historical stone sleeper in railway track construction. What both share is that they introduce concentrated loads, define edges and transitions, and must withstand mechanical and climatic stresses over long periods. In planning, maintenance, and deconstruction, precise procedures, material-appropriate processing, and low-vibration techniques are crucial—especially when threshold stones are worked in sensitive existing buildings or in the track environment. Depending on the situation, tools such as hydraulic rock and concrete splitters, concrete pulverizers, multi cutters, or steel shears may be used.
Definition: What is a threshold stone
In construction practice, a threshold stone is understood to be a massive, usually elongated component made of natural stone (e.g., granite, basalt, sandstone) or concrete that forms a threshold. In buildings, the threshold stone serves as a door, balcony, or gate threshold, separates interior and exterior surfaces, transfers loads from door frames, and protects adjacent floor finishes. In historical and museum railway construction, the threshold stone denotes the stone sleeper (sleeper block) that served as a support for rails before timber and later concrete sleepers became widespread. Both types are designed for permanent loads and are installed and fixed accordingly solidly.
Configuration, materials, and loads
Threshold stones are compact stonework or concrete components with high compressive strength and edge stability. They must safely accommodate point loads, impact and rolling loads, thermal length changes, and moisture and freeze–thaw cycles. In addition to bulk density and strength, water absorption, abrasion resistance, freeze–de-icing salt resistance, and the finishing of visible edges are decisive.
Door and floor thresholds made of natural stone or concrete
Door thresholds made of natural stone are often executed as monolithic workpieces with chamfered or rounded edges. They bridge connection joints, serve as moisture and dirt barriers, and define height offsets. In barrier-reduced configurations, threshold stones are dimensioned lower or combined with falls or channels. Concrete thresholds are found in industrial floors, hall doors, or at ramps, sometimes with reinforcement and embedded profiles.
Stone sleeper in railway track construction
Historical stone sleepers are cuboid blocks made of hard natural stone. They rest on a compacted subbase, carry rail chairs, and transfer the dynamic loads of rail traffic. Today they are found primarily on museum lines, protected sections, or as isolated finds in the subsoil and, during modifications, pose special requirements for deconstruction.
Typical dimensions and installation methods
Dimensions depend on use and load case. Door thresholds are often in the range of 20–80 mm component height (lower for barrier-reduced solutions), with lengths matching the opening width and sufficient bearing length in the jamb. Industrial thresholds and gate upstands reach several hundred millimeters and may be reinforced. Stone sleepers in railway construction are more massive and executed as cuboids with high self-weight; their geometry secures position and limits settlement. Installation is on a load-bearing, even substrate with a capillary-breaking layer, defined joints, and, depending on the application, elastic interlayers or grout.
Typical damage, aging, and inspection criteria
Over time, threshold stones exhibit damage that affects serviceability and safety:
- Edge spalling and cracks due to impact and rolling loads
- Freeze–de-icing salt damage with high water absorption and insufficient protection
- Settlement and tilting due to inadequate subgrade
- Chloride and moisture exposure in entrance areas, algae and dirt films
- For reinforced concrete thresholds: corrosion and spalling above the reinforcement
- In railway track: support shifts, breakout/spalling at drill holes and dowels
Assessment uses visual inspection, sounding, joint and bearing checks, moisture and salt indications, and, for concrete, non-destructive testing. In track-adjacent areas, positional accuracy and the connection to rail chairs and fasteners also play a role.
Deconstruction, repair, and replacement of threshold stones
In refurbishment, the focus is on joint regularity, flatness, slip resistance, and protection of adjacent components. If a threshold stone must be removed or replaced, low-dust and low-emission methods and controlled, low-vibration work practices are key.
Selective deconstruction in existing structures
In existing buildings—such as when adjusting door openings, removing gate upstands, or creating barrier-reduced transitions—a sequential approach has proven effective:
- Expose bearings and cover sensitive surfaces
- Make defined separation cuts to decouple adjacent components (dust suppression, water management)
- Split instead of hammering: use stone and concrete splitters or stone splitting cylinders to open massive workpieces in a targeted manner and divide them into manageable segments
- For reinforced concrete: pre-crush with a concrete pulverizer, then cut reinforcement with multi cutters
- Remove segments with suitable lifting gear; protect bearing surfaces
- Prepare joints and bearings professionally for replacement or rebuild
The required hydraulic output for splitters, concrete pulverizers, or multi cutters is provided by compact hydraulic power units. This enables work to be performed low-vibration and with reduced dust generation even in sensitive interior areas.
Removal of stone sleepers in the track area
When deconstructing historical stone sleepers in the track zone, confined spaces, ongoing operations, vibration limits, and heritage protection requirements must be considered. Controlled opening using stone and concrete splitters allows massive sleepers to be released with minimal impact on the subbase. Remaining metal parts such as anchors, clips, or bolts can be cut off with steel shears or multi cutters. In special cases, for example where sleepers are embedded in concrete, a combination of locally confined use of a concrete pulverizer followed by splitting is appropriate. Power supply is via compact hydraulic power packs; this supports special operations scenarios with strict emission and noise constraints.
Tool selection and equipment: criteria in controlled demolition
The choice of method depends on material, section thickness, reinforcement, accessibility, and requirements for vibration, dust, and noise. The following guidelines are common in practice:
- Monolithic natural stone with limited access: stone and concrete splitters or stone splitting cylinders for targeted opening along boreholes
- Reinforced concrete threshold body: pre-breaking with a concrete pulverizer; expose and cut reinforcement with multi cutters
- Steel inserts (anchors, profiles): cut with steel shears
- Large section thicknesses or high strength: staged drill-and-split strategy powered by adequately sized hydraulic power packs
- Sensitive surroundings: prefer low-vibration splitting methods, dust suppression and extraction, reduced separation cuts
Occupational safety, emissions, and protection of the surroundings
Work on threshold stones involves risks of cuts, crushing hazards, dust, noise, vibration, and protruding edges. Personal protective equipment, safe load handling, dust-reducing measures, and adapted working speed and pressure settings on hydraulic power packs help reduce risks. In buildings, coverings and temporary enclosures protect adjacent surfaces; in the track area, isolation and safety concepts, signalling, and involvement of responsible parties are essential. Legal requirements, technical rules, and local regulations must be observed.
Planning, logistics, and disposal
Clean separation of materials facilitates recovery: natural stone can often be reused or used as recycled aggregate; concrete goes to mineral processing; metals are collected separately. The deconstruction sequence includes access organization, utilities management (water, hydraulics), intermediate storage, and haulage. In constrained environments, compact hydraulic tools help avoid extensive site setups. Necessary permits and coordination—for example in traffic areas or occupied buildings—must be addressed early.
Application links to areas of use
Threshold stones occur across several fields; the connection to typical activities is diverse:
- Concrete demolition and special deconstruction: removal of gate and floor thresholds made of concrete, selective separation, size reduction with a concrete pulverizer and splitting
- Building gutting and cutting: opening door areas, lowering thresholds for barrier-reduced transitions, controlled separation cuts and finishing
- Rock excavation and tunnel construction: handling threshold stones in underground existing facilities or track-adjacent structures with strict vibration limits
- Natural stone extraction: production of workpieces for thresholds, quality criteria, and edge finishing
- Special operations: work in heritage areas, museums, or during ongoing operations with low-vibration methods and compact hydraulic power packs
Practice-oriented execution notes
The following approaches have proven effective for fast and safe processing:
- Before starting, clarify component build-up (natural stone vs. concrete, reinforcement, inserts); detect metals, plan water management
- Lay out the drilling pattern for splitting so that fracture lines follow the shortest paths; protect edges with chamfers
- Match hydraulic pressure and tool size to material and section thickness; perform a trial split to verify
- For concrete: first weaken the compression zone (concrete pulverizer), then cut reinforcement in an orderly manner (multi cutters), followed by segment removal
- In the track area: preserve supports, do not tear up the subbase; finally detach metal parts with steel shears
- After removal: clean bearings, check moisture barriers and falls, close joints professionally
By combining material-appropriate analysis, an orderly separation strategy, and suitable hydraulically powered tools—from stone and concrete splitters to concrete pulverizers and on to multi cutters—threshold stones can be processed precisely, safely, and with due regard for the existing structure.