Six million visitors per year leave their mark.

Kärcher is supporting large-scale deep cleaning and maintenance cleaning for the historic sandstone and mosaic floor in Cologne Cathedral. This is the second project for which Kärcher is working in collaboration with the Cologne Cathedral workshop. Kärcher experts are carrying out the first stage of cleaning, whilst also providing expertise and technology for further work to be carried out, at no cost to the cathedral workshop. Here is an overview of the challenges posed when carrying out cleaning tasks in one of Europe's most famous buildings.

Reinigung im Kölner Dom durch Kärcher

Traces left by millions of feet

The cathedral's sandstone and mosaic floor dates back to the late 19th century. Since then, up to six million visitors per year have left their mark on it, carrying dirt from the street into the historic building, which has meant that the floor's appearance has suffered: The sandstone has been covered by a layer of dark grey and the mosaics have lost their brilliant radiance underneath several layers of wax and care agents.
Together with the cathedral workshop's stone restorers, Kärcher has developed a deep cleaning and maintenance cleaning concept for the floors, the implementation of which began in March 2021. Since then, every section that is cleaned reveals another piece of Obernkirchen sandstone from beneath the layer of dirt, lime and care agents. Maintenance cleaning with scrubber driers ensures that the floor's rejuvenated old lustre is preserved for as long as possible.

Scheuersaugmaschine von Kärcher im Kölner Dom im Einsatz

Cleaning project in Cologne Cathedral

  • Construction: 1248 to 1880 (halted for approximately 300 years from 1528 to 1823)
  • Architectural style: Gothic
  • Height: 157.18 metres (northern tower) and 157.22 metres (southern tower)
  • Length: 144.58 metres
  • Width: 86.25 metres
  • Visitors: Around six million per year (before the coronavirus pandemic)
Kärcher Reinigungsaktion im Kölner Dom

The first Cologne Cathedral workshop dates back to the start of construction work for the Gothic cathedral on 15th August 1248. The cathedral workshop was re-founded in 1823/24. From 1842 to 1880, the cathedral workshop was entrusted with completing the cathedral and has been responsible for maintaining the church building since. In the first decades after 1945, the focus was on restoring significant damage to the building sustained during the Second World War. The cathedral workshop now has around 100 employees, ranging from craftspeople from various trades, restorers, engineers, archaeologists and art historians.

Kärcher is taking over the first stages of deep cleaning, and will then leave the cathedral workshop with the necessary technology to continue the works. This includes a hot water high-pressure cleaner with a FRV 30 ME cleaner.

The cathedral workshop receives a BDS 43/Orbital oscillating scrubber and a BDP 50/1500 polishing machine.

For the removal of chewing gum, Kärcher hands over a SGG 1.

Staff at the cathedral workshop will also be relying on Kärcher technology in the future for ongoing maintenance cleaning of floor coverings in the cathedral, for which Kärcher is providing a B 60 W scrubber drier for the large surfaces and a smaller battery-powered BD 38/12 C scrubber drier for areas that are more difficult to reach, such as between the pews. In addition, the cathedral workshop staff are trained in how to use and maintain the machines.

A separate sub-project is cleaning and conserving the large 1300 m² mosaic floor in the choir from the 1880–90s by cathedral workshop restorers, Jasper Völkert and Sandra Williger. Here, a layer of wax and care agents that has been applied over decades is removed using a Kärcher oscillating single-disc machine. The restorers will then carry out conservation work on the mosaic. After that, a fresh wax layer will be applied using a Kärcher polishing machine

Kölnder Dom Reinigung Sandsteinboden Kärcher

Using a hot water high-pressure cleaner in combination with a surface cleaner, dirt is removed from the pores of the 4000 m² sandstone floor in the nave with water at a temperature of 80 degrees and a pressure of 1–2 bar. The dirty water produced is immediately removed and directed away, meaning that work can be performed in a very targeted manner without spreading water and steam over a large area.

Reinigung des Mosaikbodens im Kölner Dom Kärcher

A layer of wax and care agents that has been applied over decades is removed from the mosaic floor using a Kärcher oscillating single-disc machine. The restorers will then carry out conservation work on the mosaic. After that, a fresh wax layer is applied using a high-speed polishing machine.

Unterhaltsreinigung auf dem Sandsteinboden im Kölner Dom

Staff at the cathedral workshop are using Kärcher scrubber driers in the future for ongoing maintenance cleaning of the floors in the cathedral.

Polieren der Wachsbeschichtung auf dem Mosaikboden im Kölner Dom

Scheuersaugmaschinen von Kärcher im Einsatz auf dem Mosaikboden im Kölner Dom.

Auch der Mosaikboden vor dem Dreikönigenschrein wird mit einer Scheuersaugmaschine von Kärcher gereinigt.

Grundreinigung des Sandsteinbodens mit Heißwasser-Hochdruck durch Kärcher

Der Reinigungseffekt auf dem Sandsteinboden im Kölner Dom ist deutlich sichtbar.

Die Scheuersaugmaschine von Kärcher ist auch auf dem Sandsteinboden im Kölner Dom im Einsatz.

    Cologne Cathedral

    All of the facts at a glance

    Country: Germany
    City: Cologne

    Type of soiling: Dirt from the street, occasional pieces of chewing gum, protective coats of wax
    Cleaning technology: Hot water high-pressure cleaner with surface cleaner, various scrubber driers
    For the restoration works on the mosaic floor: Single-disc scrubber, high-speed polishing machine

    Execution: Early March 2021 – ongoing