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Underground construction tunnel lined with Naue Carbofol® tunnel sealing liner, rebar and equipment along the sides, and bright work lights illuminating the wet floor.

Sealing systems in tunnel construction: installation of DWA, DWA-I and SWA

Tunnel waterproofing (tunnel sealing) is the installation of geomembrane barriers that keep water out of a tunnel structure.

Naue installs the three standard systems defined in ZTV-ING Part 5, Section 3 and the AK Tunnel guidelines — DWA (pressure water sealing), DWA-I (with an integrated injection system) and SWA (seepage water sealing) — using Carbofol® tunnel membranes. Naue holds the AK Tunnel quality mark, inspected by STUVA.

The installation of tunnel sealing systems is crucial for the safety and longevity of modern traffic tunnels. Naue is your specialist for tunnel sealing, offering tailored solutions for road tunnels, rail tunnels and cut-and-cover structures, with all seams welded and tested by DVS-2212-certified welders.

At a glance

  • Service: Installation of geomembrane tunnel waterproofing systems
  • Systems: DWA (pressure water sealing) · DWA-I (with injection system) · SWA (seepage water sealing)
  • Material: Carbofol® tunnel membrane (3 mm for DWA/DWA-I, 2 mm for SWA) on Secutex® protection nonwoven (≥ 500 g/m²)
  • Standards: ZTV-ING Part 5, Section 3; AK Tunnel guidelines
  • Certification: AK Tunnel quality mark (inspected by STUVA); welders certified to DVS-2212; seam welding/testing per DVS 2225-5
  • Typical clients: Public-sector tunnel clients (road authorities, Deutsche Bahn) frequently specify the AK Tunnel mark
Construction workers and equipment inside a large, Naue Carbofol® lined tunnel with reflective Carbofol® waterproofing membrane on the walls and ceiling.
Construction workers and equipment inside a large, Naue Carbofol® lined tunnel with reflective Carbofol® waterproofing membrane on the walls and ceiling.

Pressure water sealing (DWA)

What is pressure water sealing (DWA)?

DWA is a full-surround waterproofing system for tunnels exposed to pressing (hydrostatic) groundwater above 1 bar (more than 10 m water head). It uses a 3 mm Carbofol® tunnel membrane installed continuously around the tunnel cross-section, with construction joints secured by six-ribbed Carbofol® joint tapes to prevent water migration if the concrete cracks. DWA is particularly important in aggressive groundwater (exposure class XA3).

Why is sealing crucial?

A single membrane defect under hydrostatic pressure can cause continuous water ingress, corrosion and structural deterioration. A reliable DWA system prevents ingress, protects the structure and minimises long-term maintenance and repair costs.

Underground tunnel under construction with white Carbofol® tunnel liner, exposed rock walls, wooden formwork, and bright work lights
Underground tunnel under construction with white Carbofol® tunnel liner, exposed rock walls, wooden formwork, and bright work lights

Pressure water sealing with integrated injection system (DWA-I)

What is DWA-I?

DWA-I has the same basic structure as the DWA system for pressing water above 1 bar (more than 10 m water column), but is enhanced with an integrated injection hose network. If leaks occur after completion, sealing grout can be injected at the leak location to restore watertightness — without excavating the tunnel.

Why is sealing crucial?

In urban tunnels beneath occupied buildings or in complex geology, excavating to repair a post-construction leak is often impossible or prohibitively expensive. The integrated injection system allows quick, targeted repair of leaks or concrete faults, increasing the lifespan and reliability of the tunnel.

Large underground tunnel, tunnel sealing with Naue Carbofol® under construction with metal scaffolding, bright work lights, and workers on elevated platforms.
Large underground tunnel, tunnel sealing with Naue Carbofol® under construction with metal scaffolding, bright work lights, and workers on elevated platforms.

Seepage water sealing (SWA)

What is seepage water sealing (SWA)?

SWA protects tunnels from infiltrating seepage water where pressure is below 1 bar. It uses a 2 mm Carbofol® tunnel membrane as an umbrella seal; incoming seepage water is drained without pressure via a longitudinal drain at the invert, preventing water build-up. In highly aggressive seepage water (exposure class XA3), a single-layer geomembrane is installed around the entire structure.

Why is sealing crucial?

Uncontrolled seepage can damage the tunnel structure and the secondary lining. A reliable SWA system keeps the tunnel interior dry, protects the structure from moisture and avoids costly repairs, while enhancing the safety of tunnel users.

Benefits of having the installation carried out by a certified company?

Why choose Naue as your installation expert in tunnel construction?

  • Experience and expertise: extensive experience installing tunnel waterproofing for road tunnels, rail tunnels and cut-and-cover structures.
  • Proven materials: Carbofol® tunnel membranes on Secutex® protection nonwoven, welded on site for a long service life.
  • Certified quality: AK Tunnel quality mark (inspected by STUVA); welders certified to DVS-2212; installation compliant with ZTV-ING Part 5, Section 3.
  • Built-in repairability: the DWA-I system with integrated injection hoses allows post-construction leaks to be repaired by grout injection — without excavation.
  • Comprehensive service: from planning and material selection to installation — complete service from a single source.

What are the advantages of installation by Naue?

  • Safety and protection: a reliable waterproofing system keeps the tunnel dry and protects the structure from water-related damage.
  • Long-term cost savings: durable systems reduce maintenance and repair costs; DWA-I can avoid costly excavation for leak repair.
  • Standards-compliant installation: compliant with ZTV-ING Part 5, Section 3 and AK Tunnel requirements, with documentation for public-sector clients.
  • Adaptability: the right system (DWA, DWA-I or SWA) selected for the groundwater conditions of your tunnel.
  • Documented quality: weld log, seam-test records (DVS 2225-5) and an as-built plan for each project.

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Frequently asked questions (FAQ)

Naue installs the three standard tunnel systems: DWA (pressure water sealing), DWA-I (pressure water sealing with an integrated injection system) and SWA (seepage water sealing), using Carbofol® tunnel membranes. Naue holds the AK Tunnel quality mark, inspected by STUVA.

DWA is a full-surround system for tunnels under hydrostatic groundwater pressure above 1 bar (more than 10 m water head). It uses a 3 mm Carbofol® membrane around the whole cross-section, with six-ribbed joint tapes at construction joints.

DWA-I is the DWA system with a factory-bonded injection hose network. It is specified when post-construction leaks may need to be repaired by grout injection without excavating the tunnel — for example in urban tunnels or complex geology.

SWA is an umbrella seal for seepage water conditions below 1 bar. A 2 mm Carbofol® membrane collects seepage water and drains it via a longitudinal drain at the invert without pressure build-up.

The AK Tunnel quality mark (Arbeitskreis Tunnelabdichtung e.V.) is the sector quality mark for tunnel geomembrane installers, inspected by STUVA. It is not legally mandatory, but it is specified as a minimum requirement by many public clients (Autobahn GmbH, DEGES, Deutsche Bahn). Naue holds this mark.

Tunnel waterproofing installation follows ZTV-ING Part 5, Section 3 and the AK Tunnel guidelines. Welders are certified to DVS-2212, and seam welding and testing follow DVS 2225-5 (welding of lining membranes in tunnel construction).

Yes. Naue operates internationally; applicable local standards and certification equivalences are reviewed at the project planning stage.