The protected office building with architectural value was returned to its original use as housing
There are few rental housing projects in the inner city of Helsinki as impressive as the over 130-year-old Eerikinkatu 7. Kojamo returned the valuable office building to its original use as apartments, while preserving a piece of building history for future generations.
Kojamo, Finland’s largest private housing investment company, carried out a rare renovation project in the Helsinki city centre. Designed by architect Aimo Eklund in Kamppi, the neo-renaissance style Eerikinkatu 7 was originally completed as workers’ housing in 1892. It has been used as an office since the 1950s. The property was returned to its original purpose, and the tenants have already fallen in love with the 40 magnificent Lumo homes.
“The interior design and colour scheme that supports the architecture reflect the history of the house and clearly distinguish it from traditional new production. There has been a lot of demand for apartments,” says Toni Kankare, Director of Kojamo’s Construction Management unit.
In addition to location and history, the special features of the house include, for example, two-storey attic apartments. “It gave us a good foundation for this exceptional project that Sweco’s structural engineers have strong experience and references in this type of project,” Kankare says.
The retracted terraces were protected from sloping rain
Eerikinkatu 7 has undergone a lot of major and small alterations. In 1928, for example, a yard deck was added to the building. There is also a gold die machine still in place in the basement, which tells about the history of the premises used by the watch and precious metals company Westerback in the 1940s.
“From the same era are the basement vaults, which are made of brick and old railway tracks,” says Tero Aikkila, Department Manager at Sweco. Vaults cleaned of old filling materials and fire-retardant surfaces bring a little luxury to the cellar’s cage storage.
No changes were allowed to the street-side façade, but many of the apartments in the courtyard have new cantilevered balconies. Attic apartments with glazed retracted terraces on the courtyard side were designed to replace the former cold attic and ventilation engine room.
“Below the terraces are the wooden intermediate floors of the building, which is why we used long glass slips and other structural solutions to ensure that slanting rain does not reach the terraces even if the glazing is open,” Aikkila says.
Old logs will last for the next 100 years
The comprehensive renovation was carried out in connection with the modification project, saving old structures. The building history of the inner city can be found, for example, in intermediate floors and stairwells. The old plaster decorations on the suspended ceilings were preserved and renovated, and the colour scheme of the stairwells was restored. The solid wood beams of the intermediate floor were mainly in good condition. “Timber comparable to intermediate floor logs is practically nowhere to be found anymore, and it will last well in future use as well,” Aikkila says.
The condition surveys revealed that some of the ends of the wooden beams that extended inside the northern façade of the house had decayed. “In the end, we inspected the end of each and every beam and, together with the contractor, developed a steel extension for the rotten areas, which was used to support the ends of the beams on top of the load-bearing walls,” Aikkila says. In addition, parts of the intermediate floor beams were renewed with glulam beams. “The solution corresponds to the original, but is cost-effective.
Kojamo had an uncompromising attitude towards repairing the damage. “As a rule, we own the properties for a long time, which is why we want to carry out all repairs properly and sustainably,” Kankare says.
Architectural design raised the prestigious building to new glory
The goal of the architectural design was high-quality rental apartments. The challenge was the masonry red brick frame walls. “However, we were able to implement the apartment division without major demolition measures,” says Sweco’s architect Jukka Salonen.
As far as possible, the architects wanted to restore the old way of building and at the same time give the valuable building a new splendor. The original decorative painting of the main staircase was examined with surface layer studies, which provided a starting point for the decorative painting to be returned. “We succeeded very well, and the building got its business card back,” Salonen says.
Surface layer studies were also carried out on the facades, but the original colouring could not be determined. According to Salonen, archives and old photographs helped to find a functional decorative painting for the facades together with Mikko Lindqvist from the City Museum . “It was a pleasure to be involved in this exceptional project, sharing my expertise in sustainable development.”
Sound insulation was emphasized between the apartments
Earlier in the 50s, concrete lower slab beams had been made on different floors in connection with alterations. Now cast concrete elevator shafts were added to three staircases, and the old landscape elevator on one staircase was renewed. The partitions of apartments with old load-bearing brick or concrete structures under them were carried out by casting in situ (CIP).
“A massive wall is a good solution from the point of view of sound insulation,” Aikkila says. If there were no load-bearing structures under the partitions of the apartments, the partitions were made in the form of double-frame sheet walls. Thanks to the solution, there was no need to establish wall lines through the basement floor in the rock. “We also added mass above and below the wooden intermediate floors with new sheet structures to improve sound insulation and fire resistance.”
Sweco’s structural engineers toured the site weekly during the busiest phase. Aikkila places particular emphasis on the details of the joints between the walls and floors between the apartments. “Together with the supervisor, we checked all model performances to ensure that the sound breaks between the apartments worked. After all, the passage of just one electrical cable can ruin the sound insulation.”
Kankare is satisfied with the problem-solving skills and quick reaction of Sweco’s structural engineers on site. “These kinds of conversion projects cannot be planned on the desktop, because only after the internal demolitions do we know what really needs to be done with the structures. Smooth cooperation between the client, designers and the construction site is emphasized.”
Photos: Kojamo / Lumo-kodit