Storstrøm Bridge (Storstrømsbroen): Queen Margrethe II's Bridge

From November 2022 to March 2026, KBT Waterproofing waterproofed the new Storstrøm Bridge between Masnedø and Falster with KBT Type 5 (Eliminator®): the carriageway, railway, emergency walkways and cycle path, 98,000 m² in total, plus 15,000 m² of Decseal on the footway and cycle path. Every section was documented for climate, adhesion, film thickness and a holiday test (spark test) at 12 kV, and on the best day 3,840 m² of the full system was applied.

What was the scope on the Storstrøm Bridge?

The new Storstrøm Bridge, today Queen Margrethe II's Bridge, is a cable-stayed bridge almost 4 km long between Masnedø near Vordingborg and Orehoved on Falster, carrying a double-track railway, a carriageway, a cycle path and emergency walkways. The bridge girders were cast on Masnedø and lifted into place, and KBT carried out the waterproofing both on land, before the girders were moved, and out on the bridge itself.

KBT Waterproofing was a subcontractor to Storstroem Bridge Joint Venture (SBJV), with the Danish Road Directorate (Vejdirektoratet) as client and COWI as the client's consultant. The scope comprised shot blasting, primer, two colour-coded membrane layers, bond coat beneath the asphalt on the carriageway and Decseal Wearing Course as the wearing course on the cycle path, together with full QA documentation of every section.

Why was KBT Type 5 chosen for the Storstrøm Bridge?

Because the system could be documented before the contract was signed, and because it had already been tried on site. During the tender in autumn 2022, KBT demonstrated to SBJV that Eliminator meets the project requirements, with a complete documentation package:

• European Technical Assessment (ETA) for the two-layer Type V system and the manufacturer's factory production control.
• Ageing tests and a documented expected service life of 120 years.
• Previous approval by the Danish Road Directorate and KBT's own references, such as the Old Little Belt Bridge (Gl. Lillebæltsbro, 7,000 m²).
• A requirements matrix linking each requirement in the tender to a documented test result.

SBJV was also familiar with the system beforehand. In 2018 KBT applied 500 m² on the underpass at Orehoved as a trial area, and in September 2022 KBT carried out pull-off tests on the first five cast bridge girders before production began. The decision was therefore based on measurements from the bridge's own concrete, not just on a data sheet.

Two properties carried particular weight in practice: year-round application, because Eliminator cures in 30–60 minutes and can be applied at low temperatures, and instrument-based verification of watertightness, because a seamless spray-applied membrane can be holiday tested electrically across its entire surface. Read more about bridge deck waterproofing with KBT Type 5 and holiday testing.

How is the membrane built up on the road, railway and cycle path?

The build-up is tailored to each area. The railway and emergency walkways received the thickest membrane, because no asphalt is laid on top. The carriageway received bond coat as a tack coat for the asphalt, and the cycle path received Decseal as its finished wearing course. All layers are colour-coded so that coverage can be checked visually: a yellow first layer, a white second layer and a red bond coat.

The thicknesses are dry film thicknesses in accordance with KBT's method statement for the project. Steel surfaces were primed with Zed S94. The material was sprayed using air-driven Graco pumps (1–3 per crew), and consumption was checked against the specified rate for each component.

How did KBT achieve 3,840 m² in one day?

By having the whole chain ready at the same time: shot blasting, primer, two membrane layers and bond coat, with a separate QA crew testing behind the spray crew. On 25 April 2025, four road girders (G9N, G10N, G11N and G12N, 960 m² each) received the full system in a single day. That is 3,840 m², documented in four QA reports dated the same day.

The entire northern carriageway, 16 girders and 15,360 m², was completed between 24 April and 1 May 2025. Across 2025 as a whole, the average was 1,500–2,000 m² per working day, because the work followed the progress of the bridge and the weather. The capacity of more than 3,000 m² a day is therefore not a theoretical figure but one measured on a real bridge, and it is the reason KBT can make use of short windows when they arise.

The QA crew spent 3–4 hours a day on measurements, and the report for each girder was sent to SBJV no later than the following day. The asphalt could therefore follow directly behind the membrane without waiting for documentation.

How was every square metre verified?

The requirements were set out in the method statement, and each section was released on the basis of measurements. The climate had to be within +4 to +30 °C, with the surface at least 3 °C above the dew point, relative humidity below 90% and wind below 10 m/s. Adhesion was measured before and after application with a digital Elcometer and 50 mm dollies, with at least three pull-off tests per 500 m². Dry film thickness was measured at least every 5 m², and the entire area was holiday tested at 12 kV.

The test voltage follows the total membrane thickness. The thicker the film, the higher the voltage needed for the spark to break through a pore and trigger the alarm. On the Storstrøm Bridge the membrane is up to 3 mm dry film thickness, so the holiday test was carried out at 12 kV, higher than the 10 kV typically used for thinner build-ups.

"100% failure in the concrete" means that the concrete gave way before the bond line: the membrane adheres more strongly than the substrate itself can hold. And the 789 holidays are not a sign of weakness but the whole point of testing 100% of the area: every single pore was found and sealed while the membrane was still exposed. Individual pull-off tests below the requirement were rejected, the cause was identified and the test was repeated, exactly as a verification system is meant to work.

How did KBT work through the winter months?

The first girders were waterproofed on land in weeks 47–48 of 2022 at 5–7 °C. The railway girders out on the bridge were completed between September 2024 and January 2025, including in November, December and January at outdoor temperatures of 3–6 °C. The manufacturer permits Eliminator down to −10 °C, but the project required at least +4 °C and 3 °C above the dew point, so KBT worked with tents, drying and climate measurement for every layer.

When the climate was not within limits, no membrane was applied, and that is recorded in the report. That is the difference between being able to work in winter and doing so responsibly.

What is Decseal, and why use it on the cycle path?

Decseal Wearing Course is an acrylic-based wearing course with anti-slip aggregate mixed into the material. On the Storstrøm Bridge it was laid on top of the membrane on the cycle path from 8 September to 13 October 2025, in grey, with 15,000 m² of Decseal in total on the project. Where the substrate was too uneven, a levelling layer was applied first. The result is a watertight, slip-resistant and hard-wearing surface without asphalt, which weighs less and can be checked with the same pull-off tests as the membrane.

Read more in the blog post Decseal Wearing Course on footways and cycle paths (in Danish).

Timeline

Challenge · Solution · Result

Video: the case in one minute

Photos from the works

Frequently asked questions

See also TV 2 Øst's report from the works in TV2 meets KBT Waterproofing on the Storstrøm Bridge (in Danish).

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