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The reformed Building Act is now in force – building permits for cabins and garden saunas under 30 square metres are a thing of the past!
Under the law that came into force at the beginning of 2025, you may build on your own plot without a building permit a building that:
- is no more than 30 square metres in size and 120 cubic metres in volume;
- is not a residential building, i.e. does not contain a cooker;
- may contain a fireplace (such as a fireplace or sauna heater).
So you no longer need to apply for a building permit to build a garden sauna, aitta or cabin – as long as the building stays within that modest 30 square metres.
Building regulations must of course still be followed. However, the process becomes simpler. A permit also costs money – so the builder also saves at least 200-800€.
In practice, the size of a garden sauna usually stays under 20 square metres, although some people want to use the building for other purposes too.
If you want a larger living area with the sauna, one that allows you to put up guests or have a home office, for example, the building is still usually within 20-30 square metres. A well-designed 20-30 square metre sauna cabin offers more than ample space.
If you are planning a larger building or one intended for living in, you still need to obtain a building permit – this article also gives help with applying for one.
In this article:
Building permits for garden saunas in 2025
The new Building Act, passed by Parliament on 1.3.2023, came into force at the beginning of 2025. The act makes things easier for those considering a building permit, and for sauna builders in particular.
Municipalities have had varying practices for granting building permits, but now the granting of permits will become more uniform across municipalities. At the same time, the building permit, the operations permit and the notification procedure are merged into a single type of permit, the construction permit. There is no longer any need to apply separately for an operations permit or make a notification.
A cabin or sauna under 30 square metres no longer needs a building permit
A significant change is that all non-residential garden buildings, under 30 square metres can from now on be built without a building permit. There is also an upper limit on the volume of the buildings: 120 cubic metres. In practice, this means that the average height of the garden building must be less than 4 metres.
Only the floor area now matters for the construction permit, and no longer, for example, whether there is a sauna heater or fireplace. So you are free to build either a sauna, a sauna cabin, an aitta, a guest cabin or a home office building, as long as the building does not have a cooker.
The duty to notify applies to all buildings: so notify your municipal building control authority of every building. The duty to notify ensures that the building meets the criteria of the law and is safe for its users.
What does building control consider a residential building?
Any building with a cooker is considered a residential building. According to the guidelines, a fireplace – such as a fireplace or sauna heater – is not a cooker, so you can create the setting for a sauna lounge and sauna without going through the building permit process.
To be on the safe side, also check the other Building Act criteria below.
The Building Act – which buildings need a building permit?
Under section 42 of the Building Act, a building permit is required for the following:
1) a residential building;
2) a building of at least 30 square metres or 120 cubic metres;
3) a canopy of at least 50 square metres;
4) a public structure that can be used by at least five natural persons at the same time;
5) a mast or chimney at least 30 metres high;
6) an illuminated advertising device of at least 2 square metres;
7) an energy well;
8) an area built for a special activity that affects the use of the surrounding areas.
Finlex: Building Act 751/2023 (the act came into force at the beginning of 2025)
Municipalities and cities sometimes interpret the Building Act differently. If anything is unclear, it is always worth asking your municipality's building control for their view on your plans.
Remember to follow the building regulations
Even if the building you are planning does not require a building permit, all construction must always comply with the building regulations, the building rights set out in the local plan, and the shoreline construction regulations.
The easiest way to make sure you comply with the regulations is to contact your municipality's building control. That way you also get accurate information on municipality-specific regulations and interpretations at the same time.
How to obtain a building permit
A building permit must be obtained from your municipality's building control. The easiest way to find the building control's contact details is to search online. Applying for a building permit for a garden sauna is fairly easy and straightforward. The building permit application can be submitted in writing or electronically, for example via www.lupapiste.fiin municipalities that use the service.
To get a building permit for a sauna cabin or garden sauna, you need a bundle of different documents. It is easier to apply for a building permit for a prefabricated sauna, because the sauna manufacturer provides you with the necessary documents. If, on the other hand, you build the garden sauna yourself, obtaining the documents is up to you. No permit is needed for garden saunas under 30 square metres.
For a sauna building permit you need at least:
- a report on the flue
- a floor plan of the sauna
- a site plan
- elevation drawings
- a vertical cross-section of the sauna
- documentation of the plot
Municipal staff will help you apply for a building permit for your sauna. We at Ehtasauna are also here to help you through the process and with any questions you have.
If you are interested in a garden sauna building project and the building permit, and would like more information, please get in touch – we are happy to help!
Explore Ehta's sauna cabins and garden saunas
Remember these: building a garden sauna
Intended use
Think about what you want from a garden sauna. Will you use it in winter too? Will it serve as extra accommodation? Read more about sauna sizing in our article: Sauna sizing
Foundations
Durable, properly built foundations ensure that your sauna lasts better and does not sink, for example. Read more about choosing the right foundations in our article: The ABC of garden sauna foundations >>
DIY or bought
Do you want to build the sauna yourself, and do you have the skills? Do you have enough time? Read what a sauna costs as a DIY build or as a turnkey delivery in our article: Sauna cabin prices >>
Appearance
Do you want a traditional look for your sauna or something more modern? What colour sauna do you want? Perhaps you would like a large window looking straight out onto the lake. Read more in our articles:
Frequently asked questions about the building permit change
Do the requirements for a building permit vary between municipalities?
Since the new Building Act came into force at the beginning of 2025, buildings under 30 square metres can be built everywhere without a building permit. Municipalities can set various construction-related rules in their building ordinance, which it is worth being aware of. Municipalities cannot however, impose stricter requirements than the law for obtaining a building permit.
Is a permit needed if the building has a fireplace?
Unlike before, a fireplace does not affect whether a permit is needed. From now on, garden saunas and other buildings under 30m2 with a fireplace can be built without a construction permit.
How is it determined when a building is intended for residential use?
A building is intended for residential use if it has cooking facilities, in practice a cooker.
What information will be required in future for an application for a deviation permit?
According to current information, an application for a derogation permit will require the same attachments as now. These are an area map, a site plan, a document showing control of the building site and a report on consultation with the neighbours.
How many buildings under 30 square metres can be built on a plot without a permit?
As many as you like. The Building Act does not take a position on this. However, the local plan or the municipal building ordinance probably restricts the number of buildings.
Will there be any new red tape now that the building permit requirement is being removed?
Not as far as we know. For example, the new Building Act does not recognise a notification procedure, so no notification is needed either. The only requirement in future is to report new buildings to the Tax Administration for property tax purposes.
Can a cabin built without a permit be suitable for year-round use?
Yes, you can. The wall thickness or heating method of the building does not affect whether a building permit is needed. The only thing that matters is whether the building has a cooker. Under the Building Act, a building without a building permit may not be used for residential purposes, and a cooker is considered equipment intended for residential use.
How close to the shore can you build a garden sauna?
Minimum distances and floor area conditions for shoreline construction vary from one municipality to another. The new Building Act has not changed this. The distance from the shore required for a smallish lakeside sauna is usually around 10-20 metres.
Is a permit needed if the building will have running water and drainage
No. A water supply, sewer or, for example, electrical installation does not affect whether a construction permit is needed.
Can a garden sauna be built without a permit if the plot has no building rights?
No, you cannot. The building rights on the plot must not be exceeded. Exceeding the building rights is only possible with a derogation permit.
