Supplemental construction of a housing company

We encourage housing companies to engage in supplemental construction and provide them with help in the different phases of the process. Supplemental construction can be a good way for housing companies to finance renovation projects.

The shareholders of a housing company decide whether they will start surveying the prospects of supplemental construction. Once a decision has been made to survey the prospects of supplemental construction, the housing company board contacts the City. 

The housing company can carry out the project itself or sell a part of its plot or leasehold to an implementer. Supplemental construction can be carried out in a variety of ways. A large plot may have enough space for an entirely new building, or an existing building can be expanded. If the load-bearing structures of a building are sturdy enough, an additional storey can be built, or the attic can be converted into apartments. 

Supplemental construction always requires a change in the detailed plan. The change process always takes at least a few years. It is recommended that a housing company that owns the residential plot prepare the application for changing the detailed plan together with the City. A housing company that leases its plot from the City is required to prepare the detailed plan change application together with the City.  

Land use agreements in private land projects 

When a detailed plan is created or changed, the City and the landowner agree on the rights and obligations related to the implementation of the detailed plan. The landowner is obligated to bear some of the costs of civil construction resulting from the implementation of the detailed plan. 

The City always prepares a land use agreement with the landowner when the landowner benefits significantly from the detailed plan or the change to be made to it. 

The criterion for a significant benefit is a minimum increase of €1,000,000 in value when talking about primarily residential plots or shared yard or parking plots serving a residential plot in accordance with the detailed plan to be changed. For other types of land, the criterion is a €700,000 value increase. 

When a detailed plan for an area is created for the first time, the landowner pays the City 50% of the value increase brought about by the planning that exceeds the limit for a significant benefit, i.e. €700,000.  

When a detailed plan is changed, the landowner pays the City 35% of the value increase brought about by the planning that exceeds the limit for a significant benefit, i.e. €1,000,000 or €700,000.  

In addition to this compensation, the landowner must relinquish all public areas that it owns as determined in the detailed plan without remuneration. However, the maximum amount is equivalent to the amount of new permitted building volume determined (no more than 1 m2 of public area per 1 floor m2 of new permitted building volume). By way of derogation, in detailed plan changes in which the intended purpose is changed into a more valuable purpose, the amount of new permitted building volume is the entire amount of the change in the permitted building volume. 

The Land Acquisition Team of the Plots Unit prepares land use agreements. As a rule, agreement negotiations with the landowner are initiated once the Urban Environment Committee has approved the proposed change to the detailed plan.  

Learn more on the supplemental construction website (in Finnish and Swedish)(Link leads to external service)

Read also the following publications of the City (in Finnish): 

Contact information

You can contact us by email at: (Link opens default mail program)