A customer is choosing a garden building over the phone, and at the end asks: "I won't need a permit for this, will I?" The salesperson answers from memory: "Not under 25 square metres." The customer is happy, and so is the salesperson.
A quick answer is fine. The salesperson wants to help, and the customer doesn't want to read the law. The problem is that the answer depends on numbers the salesperson doesn't have in front of them: floor area, height, foundations, distance to the boundary. And the 25 m² figure comes from rules that no longer apply.
Whether a garden building needs a garden building permit depends on different limits in each country. In Slovakia a minor building up to 50 m² and 5 m high needs no building permit, but if it is fixed to the ground it has to be notified to the building office. In Czechia a building up to 40 m² and 5 m needs neither a permit nor a notification, provided it stands at least 2 m from the boundary and meets further conditions. In Finland a building under 30 m² and 120 m³ needs no permit, unless the municipality says otherwise. All of these numbers are already in the configuration, which is why the configurator should be the one showing them to the customer.
What "that'll be fine" costs
When the permit question is handled over the phone, it surfaces later:
- A change after signing. The customer learns the rules from a neighbour or at the office, shrinks the building, and the salesperson writes a new quote.
- A deadline nobody planned for. In Slovakia the office has 30 days to deal with a notification. Meanwhile the installation crew waits or goes elsewhere.
- An exception nobody mentioned. In Czechia a garage is never a minor building, whatever its size. In Finland, a cooker can be enough to turn a garden sauna into a residential building.
- The blame lands on the seller. The builder is responsible for the building, but they remember who told them "no need".
Nobody is doing anything wrong here. The salesperson sells garden buildings, not building law, and all three countries have had new building acts since 2024.
Garden building permit rules in 2026: Slovakia, Czechia, Finland
This is the position on 4 November 2026. The building office always decides on a specific building; in Finland, the municipal building control.
Slovakia: up to 50 m², with notification
The new Building Act, No. 25/2025, has applied since 1 April 2025. Under section 2(4), a minor building is a single-storey building fixed to the ground, with a footprint of up to 50 m² and a height of up to 5 m; the act lists sheds, summer kitchens, shelters, saunas and garages as examples. Such a building has to be notified (section 18(3)). The office has 30 days, and if it doesn't respond, the confirmation is deemed issued. A building with no foundation, no anchoring and no utility connection, not even electricity, is not fixed to the ground. According to the version on Slov-Lex, a further amendment changes the notification rules from 1 January 2027.
Czechia: up to 40 m², with no permit or notification
Under Annex 1 of Act No. 283/2021, no permit is needed for a building that meets all of these at once:
- a footprint of up to 40 m², a height of up to 5 m, one storey above ground, a basement no deeper than 3 m;
- it stands on the plot of a family house or a family holiday home and serves it, not a business;
- it is at least 2 m from the plot boundary;
- at least 50% of the plot remains able to absorb rainwater.
Residential buildings, family holiday homes and garages are not minor buildings. The footprint is measured to the outer face of the external walls.
Finland: under 30 m² and 120 m³
The Building Act, rakentamislaki 751/2023, has applied since 1 January 2025. A permit is needed for a residential building of any size, for a building from 30 m² or from 120 m³, and for a shelter from 50 m². A municipality can set further rules in its building ordinance, and municipalities measure the area differently. No permit doesn't mean no rules: Helsinki, for example, requires unused building rights on the plot and a 4 m distance from the boundary unless the local plan says otherwise.
What the configurator should show
The law works with the same numbers as the configuration. The configurator can therefore show them while the customer is changing the size, not after signing.
The footprint, measured the way the law measures it
In Czechia, the outer face of the walls decides, not the floor area in the brochure and not the roof with its overhang. A customer who sees "38 m² footprint" doesn't have to convert anything.
Height and volume
The 5 m limit in Slovakia and Czechia can be exceeded by a steeper roof without changing the plan. In Finland the 120 m³ volume decides too, and no customer works that out in their head.
Equipment that changes the category
In Slovakia, anchoring, ground screws and a utility connection make the building one that is fixed to the ground. In Finland, what matters for a sauna is whether it has a cooker; according to the Association of Finnish Municipalities' commentary, a fireplace or a sauna stove does not make it residential. In Czechia, a residential building is never a minor building, whatever its size.
The country of the building, not the language of the website
A customer from Slovakia may be building a cabin in Moravia. The notice should follow the country of the building, with a reference to the law.
Our garden building engine is in preparation, and it does exactly this: on every change it compares the footprint and height with the country's limit, shows the law and, in Czechia, reminds the customer of the 2 m distance and the rainwater rule. The carport engine, also in preparation, knows the Finnish limits of 30 m², 120 m³ and 50 m². Neither ever says that no permit is needed. It says what numbers the configuration has and what follows from them under the law.
When not to put this in a configurator
Not every seller needs it:
- You handle the design and the notification for the customer. If you have your own designer, the permit question is their job, and a configurator would only duplicate it.
- You sell into one country and every model falls under the same regime. One sentence next to the models says the same as a notice on every change.
- You can't keep the rules up to date. Laws change, the Slovak one again from 1 January 2027. An out-of-date notice is worse than none.
If you didn't recognise yourself in any of these, carry on.
A five-minute test: who answers the permit question?
- Does the salesperson know the limit for the country you install in? If they say 25 m², they are quoting rules that no longer apply.
- Does your brochure measure area the way the law does? Floor area and footprint are not the same number.
- Do you ask about the distance to the plot boundary? In Czechia and Finland it decides whether the building goes ahead without a permit.
- Who tells the customer about the notification? If nobody, they hear it from the neighbour.
The first step takes five minutes: write down the footprint, height and volume of every model. A model close to a limit deserves a note today.
Where permit limits decide
- Garden buildings and sheds: footprint, height, foundations and distance from the boundary.
- Saunas: in Slovakia the act lists them as minor buildings, in Czechia the ministry's guidance does, and in Finland the equipment matters too.
- Carports: in Czechia a separate item up to 40 m², in Finland a shelter up to 50 m². More in A carport isn't a small pergola.
- Garages: in Slovakia a minor building up to 50 m² with notification, in Czechia never.
The full list of 305 product types is in the configurator catalogue.
Frequently asked questions
Does the 25 m² limit still apply?
Not in Slovakia or Czechia. In Slovakia, since 1 April 2025, the limit for a minor building is 50 m² and 5 m; in Czechia, under the current text of the act, it is 40 m² and 5 m with the conditions above.
Does a building in Slovakia have to be notified?
Yes, if it is fixed to the ground: it has a foundation, anchoring or a utility connection. The builder files the notification with the building office, which has 30 days.
Does the roof overhang count towards the footprint?
In Czechia the footprint is measured to the outer face of the external walls. In Slovakia and Finland local interpretation applies, so it is worth checking with the office.
Does a garden sauna need a permit?
In Finland not, if it is under 30 m² and 120 m³, has no cooker and the municipality has no stricter rules. In Slovakia it is a minor building with notification; in Czechia a minor building under the conditions above.
What now
And the question "I won't need a permit for this, will I?" Let it be asked. Just let the configurator answer it with numbers and the law, and let the salesperson add one sentence: check with the building office.
If you sell garden buildings or saunas into more than one country, see what a configurator with treede CRM costs.
