How Do You Convert an Office Space into Apartments?
In the Helsinki capital region alone, there are currently around 50 city blocks’ worth of empty office space. On the other hand, there seems to be a constant demand for housing. Under what preconditions are office spaces converted into apartments?
In 1961, a building for small-scale industries was built in the middle of a rocky outcrop in the Helsinki district of Alppila. The Alppila Industry House was meant to withstand many uses. At that time, new industrial construction technology enabled greater systematisation, and so the building’s architects, Kaija and Heikki Siren, designed a deep T-shaped floor plan that could be flexibly divided for different uses.
A regular 5.6×8-metre load-bearing grid of columns runs through the entire building. The free ceiling height is 2.6 metres, and the frame depth is 21.5 metres. Presently, the building houses dozens of tenants from a yoga studio to the editorial offices of a magazine for a political party.
The Sirens could hardly have envisioned, however, small-sized apartments being inserted into the building. In 2020, the owners applied for an amendment to the detailed plan for the site, in order to demolish the building and build in its place an apartment block.
In Finland, office and industrial buildings are demolished on average at a younger age than residential buildings – at slightly less than 40 years old.1 Alppitalo has already lasted more than 20 years longer than that.
In the time of the climate crisis, nothing should be demolished. If the use of a building is changed or only its structural frame preserved, the carbon footprint resulting from the necessary new materials and additional construction is still on average only a little more than half of the carbon footprint of a completely new building, according to the research report Purkaa vai korjata? [Demolish or repair?] published by the Finnish Ministry of the Environment in 2021.2
At the end of 2020, there were more than one million square metres of empty office space in the Helsinki capital region alone,3 the equivalent of about 50 apartment blocks. When there is also at the same time a significant demand for housing, it would seem logical to be able to change the use of buildings.
However, the conversion of business premises into apartments still seems to be carried out on an individual basis, as pilot projects and experiments. Sustained operating models have not yet emerged.
What parametres do conversion projects currently face, and what kind of housing solutions materialise from them? Is it even worth converting business premises into apartments if it means making too many compromises? Would it be possible to convert the Alppila Industry House into apartments?
Location and Narrative as Assets in Conversion
Less than two kilometres from the Alppila Industry House, in the Helsinki district of Töölö, the advertising hoardings, hanging in front of the windows of a building built from grey exposed aggregate concrete prefabricated panels, tell about the ongoing changes.
The office building by architect Matti Hakala along Manner-heimintie was completed in 1979. Two sides of the U-shaped building included apartments already from the beginning. But now the office wing is being converted for residential use. The developer Newil&Bau, founded two years ago, bought the office part from the housing management company.
“We are mainly interested in the location and unique architecture. We build new and renovate old buildings. We always want to keep the existing one if possible. In principle, it doesn’t matter if it’s a renovation project”, says the Newil&Bau CEO Petri Ylivuori.
This is Newil&Bau’s second project in which former business premises are converted into apartments. The developer made their first apartment conversions in Alvar Aalto’s Insinööritalo (1951) office building in Helsinki’s Punavuori district. It will be possible to live along this part of Mannerheimintie from the beginning of 2024.
Ylivuori talks about the company’s design philosophy and dwelling as a consumer product. “We’re not trying to make merely walls and ceilings, but to create living experiences”, he explains. “Spirit and soul are the objectives, and it’s easier to create those in old houses, because the house already possesses a ready narrative.”
Unlike the Insinööritalo building, Mannerheimintie 76 is not a protected building. Instead of conserving, creating interesting architecture and spirit need somewhat more reinventing.
In renovation projects, surprises and exceptions will almost inevitably materialise. When it comes to cost control, Ylivuori believes in careful advance research: “Everything starts with a systematic approach. All critical parts are examined.”
So where, then, are the limits? When, according to Newil&Bau’s criteria, does a building not yield to change?
“We always contemplate whether we are able to create high-end apartments in the building”, says Ylivuori. “If the floor-to-floor height of the building is less than three metres, the frame depth is large or the technical condition is too poor, renovating it into high-quality apartments is unfortunately very difficult.”
The Architect’s Skills Are Necessary
The detailed plan for Mannerheimintie 76 was favourable: it stipulates that no more than 4,000 square metres of office and retail space can be placed on the plot, so there was no need to ask for an amendment to the detailed plan. Also, there was already a parking garage beneath the courtyard and the building.
Architect Mika Penttinen took on the task of studying the 16-metre-deep structural frame. It is almost 6 metres deeper than in the adjacent part designed already at the outset for apartments. The stairwells were located at the ends of the building – as was often the case in office buildings of the time. Apart from the structural columns and beams, everything else in between could be dismantled.
In Finland, apartments undergoing conversions are subject to the same regulations as new apartments, and so compromises have to be made. There are no ready spatial solutions to be found in design manuals.
Penttinen is inspired by the conversion projects: “This is exactly what an architect is needed for. There are no obvious solutions.”
Because the side of the building facing Mannerheimintie is noisy and dusty, they did not want to create apartments that only overlook the street. Instead, the street side is now lined with access corridors, while the central part of the building comprises double-aspect apartments. The rooms along the access corridors do not have windows facing directly out, but receive light from the corridor via a glass-brick wall.
“This is of course not a universal solution, but in this particular case it solved the problems of the structural frame”, says Penttinen. According to the building regulations, daylight can be supplied to some of the habitable rooms via another space.
The design of the apartment floor plans was also guided by the technical infrastructure. All bathrooms and kitchens were placed in the centre of the frame between the beams. Consequently, at the centre of all the apartments is a lower 2.3 metres high enclosed ceiling that hides the technical installations.
Penttinen has had a long relationship with the building. He worked in Matti Hakala’s office in the 1970s, when Manner-heimintie 76 was being designed on his colleagues’ worktables. In the conversion, the goal is “to strengthen the good features of the original architecture and diminish the less favourable ones.”
For example, the former bank’s sauna, used for entertaining business partners, located in the old residential end, will be renovated for the use of all the residents in the upcoming pipework renewal.
On the other hand, Penttinen has tried to lessen the amount of the colour brown typical of Matti Hakala. Stained oak has been changed to a natural colour. In the marketing material, the atmosphere inspired by the 1970s, with its glass bricks and exposed concrete pillars and beams, is called an “industrial spirit”.
A Conversion Turns the Building Project into a Work of Craftsmanship
Architect Riikka Kuittinen has also given consideration to the spirit of the 1970s and the opportunities it offers, on the other side of Finland. She is a partner in Luo Architects, who designed the conversion of the SYP Bank’s underutilised bank and commercial building in Kuopio, sited near the market square, into apartments and commercial spaces. An additional floor was built on the roof of the former bank and a new four-storey extension was built on top of the lower part.
“A bank embodies something completely different from residential buildings. It is solemn, imposing, and aloof. Housing, on the other hand, is preferably something cosy and inviting”, Kuittinen muses. At the same time, there is something exciting about the architecture of the 1970s.
The Finnish Heritage Agency was particularly interested in preserving the spirit of the main facade and the banking hall of the protected building, completed in 1977. The glass-roofed banking hall was renovated to resemble the original. The main facade, based on a 60-centimetre grid, already had the appearance of a glazed facade, although in reality there was a solid wall surface behind every second square of the grid. Now each of them was changed to a window to bring more light into the apartments.
One key factor in the planning was that there was already a two-storey parking garage beneath the building. In Kuopio, the number of apartments is regulated indirectly through apartment-specific parking space requirements: when you run out of parking spaces, you have to build bigger apartments.
The designers strived for repetition as much as possible, but due to the and existing structures and , in the end every storey is different. Some of the apartments also are on two floors.
If it had been a new building, it might have had more balconies and outdoor spaces, Kuittinen notes. Now, in the old part there are balconies only on the yard side, while in the new part they are on both the long sides.
Kuittinen finds it disappointing that the old structural beams could not be left exposed in the apartments, so as to add character, but it would have involved too much work to clean them up.
“I imagine that it would definitely be a selling point that the ceiling is high and the beams are exposed. But according to the developers, in these types of properties, the buyers only look at the location.”
Due to the advancing climate change, the focus of construction must shift from new construction to renovation. Kuittinen sees also positive sides in climate-friendly renovation is being more labour intensive than new construction.
“A more sustainanble future will definitely will not mean less work in the construction industry”, she reflects. “Then it’s just a question of who will pay for the larger workload.”
The bank conversion project was a conventional commercial construction project of the developer Lehto Group. The price per square metre of the apartments in the centre of Kuopio is less than half of the price in Töölö in Helsinki. How can the project be kept profitable?
“It’s not necessarily worth it. In the future, we will only do such projects if more new construction can also be done on the plot”, says the Lehto Group’s construction manager Juha Räisänen, who supervised the work on the Kuopio site.
According to Räisänen, it is important for the Lehto Group to be able to build according to its own concept, which is based on prefabricated bathroom-kitchen elements and optimising the design process around them. It is impossible to lift these elements into an existing building frame.
A Platform for New Housing Concepts
Is it the case, then, that conversion projects are only profitable at the prices per square metre generated near the centre of Helsinki? On the web pages of the City of Helsinki’s Re-thinking Urban Housing programme, one can find Hoas Hima, a former office building in East Helsinki converted into student housing, where the average price per square metre of the apartments is close to the price level of the centre of Kuopio.
Investigating the cost effectiveness of conversion projects is mentioned as one of the project’s objectives.
The Re-thinking Urban Housing programme aims to increase the quality and attractiveness of living in an apartment building and to develop new individual solutions. Hoas Hima is the programme’s first, and so far, only renovation project, says the programme’s coordinator, special planner Riikka Karjalainen from the City of Helsinki.
The student apartments were built in place of older planning visions: when the Rastila metro station was completed in 1998, the areas next to it were planned for use as office buildings. However, there was little demand for offices in East Helsinki, and gradually the detailed plan was changed on a plot-by-plot basis to housing. Even the tenants of the only office building to be built, completed in 2001, gradually moved to more central locations, such as Pasila.
The owner decided to offer the building to the Foundation for Student Housing in the Helsinki Region HOAS, as a new type of student dormitory, with micro apartments and generous common spaces, such as shared kitchens and workspaces. HOAS took an interest in the concept, as the university campus in Myllypuro is just three metro stops away.
koulukampus on kolmen metropysäkin päässä.
The location next to the metro line does not meet the regulations regarding the noise limits of ordinary apartments, but is adequate for student housing. The old room division of the offices and the placement of the windows were also suitable for a student dormitory, where the room size must be at least 16 square metres. The student apartments in Hoas Hima are slightly larger than this. Also sleeping lofts create extra space in the narrow apartments.
Cost efficiency was sought through repetition. Adjacent apartments were made as mirror images of each other, so that the shafts for the technical infrastructure in the bathrooms could be combined.
“The work on the building site progressed like serial production: it was precisely defined who would do what work in a certain apartment before moving on to the next one”, says architect Jaakob Solla from the architecture practice Konkret, who planned the conversion.
Student housing is covered by the government’s Ara regulation, so already that helped in keeping the costs reasonable. Kim Lindholm, HOAS’s real estate director, sees the project as a breath of fresh air among the otherwise rather monotonous residential construction.
“Could such a project be done more cost-effectively? Certainly. But if suitable places and affordable building frames can be found, then we could definitely consider taking on a project like this again. Through Hoas Hima, we have gained some useful knowledge on this type of projects.”
Flexibility is a key theme in the Re-thinking Urban Housing programme. So far, it has been approached through the flexibility of the apartments and not from one function to another, says Riikka Karjalainen. As she sees it, conversion projects are currently client-oriented: they are carried out if the owner of the building so desires.
Therefore, within the framework of the Re-thinking Urban Housing programme, there are plans to give one of the city’s own underutilised properties as a development project. Ideas could then proactively be sought for.
The Strengths of a Systematic Building
Architecture student Heikki Myllyniemi is currently working on his diploma thesis on the development of the area surrounding the Alppila Industry House. For the Industry House’s exceptionally deep 20-metre structural frame, he has placed apartments of the size that are currently produced within the. He minimised the depth of the actual living quarters by placing semi-warm summer rooms against the exterior wall, which would also enable better fireproofing and additional thermal insulation.
“In my plans, the conversion to apartments looks doable. The structural frame is super generic in a good way. The technical infrastructure and making holes in the structures is, of course, a separate issue. The experts will examine that”, says Myllyniemi.
The Alppitalo plot is currently being redeveloped by Newil&Bau together with the owners. As yet, they do not want to comment on the project. The amendment to the detailed plan is in progress. The public participation plan became available for public viewing in May 2022.
The starting points may be difficult, but the Sirens’ systematic approach would definitely deserve a longer lifecycle and housing production more creative ideas. ↙