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A significant renovation project was carried out on the two buildings of the Supreme Administrative Court, located near Helsinki’s Kasarmitori, and completed in November 2023.

In a nearly two-year project, TKR’s biobased coating played an important role, as a large amount of health-hazardous creosote was found in the walls of the buildings’ underground spaces.

Use of spaces had to be restricted due to the hazardous substance

The Supreme Administrative Court’s premises consist of buildings completed in 1902 and 1952, located on Fabianinkatu in Helsinki’s Kaartinkaupunki.

The renovation project of the buildings focused on updating the building services, and the buildings’ conservation values presented their own challenge to the restoration construction.

In the buildings’ basement spaces workers detected structures built with creosote masonry. The discovery of cancer-causing creosote and asbestos is natural for buildings of these eras.

Picture 2. Underground, creosote was mixed into the mortar, which was used to treat all surfaces of the underground spaces, pillars, and partially the ceilings.

Before the renovation project, the use of the basement spaces had been significantly restricted for a long time due to the hazardous substances.

The substances encountered were intended to be removed from all possible locations. However, especially with load-bearing walls, removing creosote is very difficult. Therefore, the removal operation required careful planning and precisely chosen measures to avoid future problems.

Creosote was successfully encapsulated within the walls

Sandblasting or demolition are not self-evident measures in all cases, as they thin the surface of the structure so much that load-bearing issues may start to arise.

Even if creosote could be removed, sanded, or blasted away, the concrete must be encapsulated afterwards, as the substance typically penetrates deep into the structures.

In the project, all basement wall surfaces were sandblasted and diamond ground, after which the walls were treated three times with TKR coating. This way, the spaces were encapsulated, and nearly 400 m² of underground space became safe for use again.

Picture 3. The basement walls were treated with TKR coating three times.

Due to the building services repair works, some holes had to be made in the creosote-bricked walls. The amount of the holes was minimized to prevent harmful compounds from entering the spaces beneath the coating.

The encapsulation was maintained in such a way that sleeves, which also received TKR treatment, were first installed in the holes. After that, drain pipes, into which the HVAC technology was installed, were inserted into the holes.

Thanks to the odorlessness and safety of TKR, the concrete workers working in the spaces could work simultaneously, thus avoiding the need for masks and partitioning altogether. Working in the basement’s air quality would have been very challenging during the project’s hot summer days, so the odorless coating solution significantly eased the work.

Picture 4. Thanks to the biobased coating solution, the Supreme Administrative Court’s underground premises will remain free of hazardous substances well into the future.