Building close to the neighbour's boundary – distances and rules 2026

The basic rule in 2026: within a detailed-plan area, a building's position is set by the plan – the buildable area and the plan provisions. If the plan says nothing else, the typical requirement is a distance from the boundary of at least half the building's height, but no less than 4 metres. Outside detailed-plan areas, the distance comes from the municipal building ordinance, and in recent ordinances the threshold is typically 4–5 metres. You may only build closer with the neighbour's written consent – and even that does not override the fire regulations.

Why does the old 5-metre rule no longer apply as such?

Many remember the old nationwide rule of thumb: 5 metres from the neighbour's boundary and 10 metres from the neighbour's building. It came from Finland's Land Use and Building Decree, whose construction provisions were repealed at the start of 2025 when the Building Act (rakentamislaki) came into force. Distances are now set by the municipal building ordinance. In new ordinances the threshold is often 4 metres – Kirkkonummi's 2025 ordinance requires four metres unless otherwise agreed in writing with the adjoining neighbour – while older ordinances commonly say 5 metres. Your own municipality's ordinance is the only reliable source, available on its website or from building control. Never build on the strength of an out-of-date figure.

The fire regulations' 8-metre rule

Distance from the boundary is not the same as distance from the neighbour's building. If the gap between buildings – including one on the neighbour's side – is under 8 metres, fire spread must be limited structurally, in practice with compartmentation and EI-rated structures. Rule of thumb: 8 metres of clear space, no compartmentation needed. The assessment is project-specific, and on tight plots a compartmenting wall is common for a garage or store at the plot edge. A timber or log building is no obstacle – compartmentation comes from the structure, not from banning materials.

One-sentence memory aid: a neighbour's consent can shorten the distance to the boundary, but it never removes the fire requirements.

The neighbour's written consent

To build closer to the boundary than the plan or building ordinance allows, you need the neighbour's written consent, stating what it covers – many municipalities have a ready-made form. A verbal promise is not enough and offers no protection when the property changes hands. Neighbour consultation is part of the permit attachments anyway, so sort the consent out at the same time. Consent is only one precondition: the municipality weighs the siting as part of the permit, and the fire regulations apply regardless.

Do the distances also apply to permit-exempt buildings?

They do. A sauna or store under 30 m² needs no construction permit, but must still meet the building ordinance's distances – typically 4–5 metres from the boundary without consent. This is the commonest stumbling block: the exemption gets read as freedom to place the building anywhere, and neighbour disputes over saunas near the boundary are rising. The municipality can afterwards order a non-compliant building moved or demolished.

Why stick to the distances?

The distance rules serve three purposes. They limit the spread of fire from one building to another, secure reasonable light and outlook for the neighbour, and leave room for maintaining the building – painting a wall or repairing the eaves from the neighbour's side is not a sustainable plan. The new permit exemption changed none of these fundamentals; it only changed who checks that the requirements are met: the builder themselves.

How to proceed on a tight plot

• Check the buildable area and boundary distances in the plan – within a detailed-plan area, the plan comes first
• Read your municipality's building ordinance: is the boundary distance 4 or 5 metres?
• Measure the distance to the neighbour's buildings too – a gap under 8 metres triggers fire compartmentation
• Get the neighbour's consent in writing on the municipal form if you plan to build closer to the boundary
• Discuss your plans with the neighbour in advance even if consent is not needed – consultation is part of the permit process anyway

Building close to a boundary works when the order is right: first the plan and building ordinance, then the fire assessment, then the neighbour – and only then the foundations. A building in the wrong place is the most expensive way to learn the rules. One call to building control before starting work repays itself many times over: the inspector will tell you what the plan and ordinance require on your plot, and often what solutions have been approved on similar plots.

• Within a detailed-plan area the plan determines the building's position; elsewhere it is the municipal building ordinance.
• The typical minimum distance from the neighbour's boundary is 4–5 metres without the neighbour's written consent.
• The old decree-based 5-metre rule was repealed on 1 January 2025 – distances now come from the building ordinance.
• A distance under 8 metres from the neighbour's building requires structural prevention of fire spread.
• The neighbour's consent must be in writing, and it never overrides the fire regulations.
• Even a permit-exempt building under 30 m² must be sited according to the building ordinance's distances.