Installation day: how a shelter module reaches your property

Preparation: pit and foundation

Groundworks begin several days before delivery in accordance with DIN 18300 and the project-specific geotechnical survey. Excavation dimensions must accommodate the structural footprint of the precast unit, the external waterproofing perimeter, and adequate working space required under safety regulations. Depending on the soil classification and depth, the pit sides are either sloped at stable angles or secured with trench shoring to prevent soil collapse during installation.

Subsoil stability dictates the foundation design beneath the shelter. After removing loose earth down to undisturbed load-bearing strata, contractors place and compact a mineral sub-base to prevent differential settlement. A level concrete blinding layer, typically non-reinforced C12/15, is cast over the compacted gravel. This working surface provides an unyielding, horizontal plane that protects the underside waterproofing barrier and ensures the shelter body aligns precisely without tilting.

Level tolerances on the blinding layer must remain within millimetre precision. Any angular deviation directly affects the geometry of blast-protected doors and pressure-tight hatches, which rely on exact axial alignment for gas-tight sealing. Drainage sleeves, earthing connections conforming to DIN 18014, and pipe penetrations must be accurately positioned and surveyed prior to crane arrival to avoid structural modifications during placement.

• —Geotechnical soil assessment and classification
• —Pit excavation with compliant slope angles or shoring
• —Placement and plate compaction of mineral sub-base
• —Pouring of a calibrated, level concrete blinding layer
• —Installation of foundation earth electrode per DIN 18014

Crane appointment

Prefabricated modular shelters present concentrated heavy loads that require specialised transport and lifting assets. Units travel to the site on heavy-duty low loaders under relevant transport permits. Lifting is conducted by an all-terrain mobile crane, sized according to unit weight, radius, boom length, and local site geometry. Transport routes are surveyed in advance to verify road load limits, axle allowances, bridge clearances, and turning circles.

Positioning the crane requires a verified, stable setup area capable of supporting high outrigger ground-bearing pressures. Steel spreader plates or heavy timber outrigger mats are deployed to distribute point loads safely across the subsoil or paved access roads. The lift radius is calculated with strict tolerances to prevent crane overloading, taking into account the horizontal distance between the crane pivot and the pit centre.

Urban and suburban settings demand rigorous spatial management. Obstacles such as overhead medium-voltage cables, mature trees, street lighting, and neighbouring boundary structures restrict crane slewing paths and counterweight clearances. Where cranes occupy public highways, local traffic authorities must issue formal road-closure permits and temporary parking restrictions under the road traffic act well in advance, ensuring uninterrupted access for transport vehicles.

• —Verification of transport route access and bridge capacities
• —Geotechnical check of crane setup area and outrigger pads
• —Acquisition of municipal road-use and road-closure permits
• —Assessment of overhead lines, vegetation, and clearances
• —Implementation of pedestrian barriers and safety exclusion zones

Module placement and alignment

Once the low loader arrives and the mobile crane is fully ballasted, certified lifting tackle is attached to the cast-in lifting anchors of the shelter. The lift follows DGUV safety regulations for crane operations, supervised by a qualified banksman. The precast unit is hoisted smoothly from the trailer bed, rotated into its correct spatial orientation, and slewed over the excavation pit using tag lines.

The module is lowered slowly onto designated elastomer bearing strips or a polymer-modified mortar bed on the blinding layer. Lowering speeds are strictly controlled to prevent dynamic impact loads on the foundation. Banksmen guide the unit into its exact coordinates using optical surveying equipment, verifying that structural wall lines align with pre-installed service sleeves, escape tunnels, and external drainage pathways before releasing the crane load.

After the unit settles, the rigging crew detaches the lifting chains, and technicians conduct immediate alignment checks. High-precision digital levels verify transverse and longitudinal horizontal planes. Correct alignment ensures that heavy gas-tight blast doors operate without mechanical resistance and that drainage falls on the roof slab direct surface water toward external collection channels rather than allowing water to pool against wall joints.

Waterproofing and connections

Below-ground civil-defence structures require robust moisture and gas protection conforming to DIN 18533. External concrete walls receive multi-layer waterproof barrier systems, such as polymer-modified bitumen coatings or fully bonded elastomeric membranes, designed to resist pressing groundwater and soil dampness. Where modular units are joined together or connected to external escape tunnels, compression seals and internal swellable joint tapes are installed across every structural interface.

All service penetrations through the reinforced concrete shell represent potential weak points for gas and water ingress. Fresh-air intakes, exhaust-air ducts, electrical supply cables, communication conduits, and wastewater lines are routed through pressure-tested, gas-tight wall transits. These specialized pipe and cable seals utilise high-grade elastomer segments compressed by stainless-steel pressure plates, ensuring certified resistance against hydrostatic pressure, subterranean moisture, and airborne chemical contaminants.

External perimeter insulation boards, manufactured from extruded polystyrene with high compressive strength, are placed against the waterproofing layer before backfilling. This insulation protects the structural membrane from mechanical puncture during backfill compaction and prevents thermal bridging within the protected envelope. Concurrently, foundation drainage pipes wrapped in geotextile filter fleece are laid around the base perimeter to manage surface water runoff according to DIN 4095.

• —Application of external waterproofing conforming to DIN 18533
• —Installation of elastomeric compression seals across joints
• —Fitting of certified gas-tight and pressure-tight wall transits
• —Placement of perimeter insulation boards to protect membranes
• —Laying of perimeter drainage with geotextile filtration per DIN 4095

Backfill and earthworks

Backfilling the excavation pit must proceed systematically to safeguard structural stability and membrane integrity. Only non-cohesive, free-draining mineral materials, such as gravel-sand mixtures or certified recycled aggregates of specified grading, are approved for shelter backfill. Cohesive soils, expansive clays, and rubble with sharp edges are unsuitable, as they exert uneven hydrostatic pressure and risk lacerating external waterproof membranes during compaction.

The backfill material is introduced symmetrically around the shelter perimeter in horizontal layers not exceeding thirty centimetres in loose thickness. Each lift is compacted using light, hand-operated vibratory plate compactors. Heavy compaction equipment is prohibited adjacent to the structure to prevent excessive lateral earth pressures that could distort the reinforced concrete walls or displace the module from its calibrated foundation bed.

Earth cover over the roof slab is placed in accordance with the structural design calculations and protection specifications. In addition to contributing structural mass for radiation shielding and blast attenuation, this soil overburden must be sloped to promote natural surface water run-off away from air intake vents and access shafts. The uppermost soil layer is restored with topsoil suitable for replanting garden vegetation.

Handover and briefing

Following mechanical installation and civil works, a structured commissioning protocol is conducted. Certified technicians test all functional components, starting with heavy blast valves, overpressure release valves, and hermetic door seals. Pressure differential tests verify that the module maintains the airtightness required for CBRN filtration mode. Electrical systems, backup battery arrays, and automatic changeover switches are systematically verified under simulated mains failure conditions.

The mechanical ventilation and air filtration unit is test-run in both electric and manual crank modes. Technicians measure airflow rates against calibrated design benchmarks to guarantee that fresh-air supply complies with technical guidelines for protective shelters issued by the Federal Office of Civil Protection and Disaster Assistance (BBK). Stock levels of pre-filters, HEPA filters, and activated carbon filter canisters are inspected and sealed in airtight storage boxes.

The installation concludes with an in-depth operational briefing for the property owner. Technicians explain routine maintenance intervals, emergency operating procedures, filter replacement protocols, and manual overpressure regulation. Complete technical documentation, including structural drawings, conformity certificates, maintenance logbooks, and statutory warranty documents, is formally handed over. This comprehensive briefing ensures that the shelter remains fully operational, self-sufficient, and dependable in any emergency scenario.

• —Verification of door seals and blast valve mechanical operation
• —Functional testing of CBRN filtration and manual crank drive
• —Measurement of differential air pressure and airflow rates
• —Verification of electrical backup systems and emergency lighting
• —Provision of maintenance logbooks and manufacturer documentation