Short answer
What you need to know first.
In Canton Solothurn, sufficiently integrated PV systems on roofs and facades generally require notification rather than a building permit. The site municipality receives the notification form with building description, site plan and facade plan no later than 30 days before construction starts; protected objects and the cantonally designated protection areas trigger a building permit.
Important
As of 2026, the key boundary in Canton Solothurn is not module size alone, but protection status and compliance with the RPV design criteria. According to the Solothurn form, solar systems outside roofs or facades, for example on a noise barrier, always require a building permit; systems outside the building zone additionally need approval from the Department of Construction and Justice.
Decision points
What determines the right path.
The first filter is Art. 18a RPG: in building and agricultural zones, sufficiently integrated solar systems on roofs or facades generally do not need a building permit, only notification. In Solothurn this does not mean "just build", but a formal filing with the site municipality under § 3bis KBV.
For pitched roofs, Art. 32a para. 1 RPV decides integration: a maximum 20 cm perpendicular projection, no extension beyond the roof surface, low-reflection execution and compact arrangement. If one of these points is not met, the Solothurn form classifies the system as requiring a building permit.
For flat roofs, Art. 32a para. 1bis RPV applies: the system may project no more than 1 m above the top edge of the roof parapet and must be set back far enough not to be visible from below at a 45-degree angle. These exact values belong in the section or facade view before the quote.
Solothurn explicitly names cantonal protected cases: the old towns of Solothurn and Olten, Balsthal village core, protected historic cultural monuments, protected areas of the Jura, Engelberg, Born, Bucheggberg and outer Wasseramt, as well as townscape protection zones and areas of particular beauty and character. In these cases the local building authority starts the ordinary building application procedure.
The documents are not a side issue: § 3bis KBV and the Solothurn form require a building description, site plan and facade plan. If a plan is missing or the module height is not visible, the municipality cannot reliably decide notification versus building permit.
From 30 kWp, the Solothurn notification form points to the fire brigade plan requirement; it also asks whether grid-operator clarification has shown additional line construction projects or transformer stations. These points can affect the schedule more than the pure 30-day building notification period.
Sequence
How the project stays cleanly managed.
- 1
Check the locationbefore the quote, clarify whether the building is in the old town of Solothurn or Olten, in Balsthal village core, in the Jura protection zone, in a townscape protection zone or on a protected historic cultural monument. A hit does not automatically mean prohibition, but in Solothurn it means a building permit requirement.
- 2
Classify the system typefor pitched roof, flat roof or facade, check the requirements from Art. 32a or Art. 32abis RPV. The 20 cm rule on pitched roofs, the 1 m value on flat roofs and 45-degree visibility must remain visible in the planning.
- 3
Prepare grid and capacitybefore filing, clarify with the grid operator whether line construction projects or a transformer station will be needed. For systems from 30 kWp, also classify the fire brigade plan requirement named in the Solothurn form with the Solothurn building insurer.
- 4
Prepare documentsprepare the building description, site plan and facade plan so that location, module area, mounting height, roof edge, facade relationship and low-reflection execution are traceable. The form requires these attachments as mandatory and signed.
- 5
Submit the notificationfile the complete notification form with the local building authority of the site municipality no later than 30 days before construction starts. Based on the left or right answer options in the form, the municipality decides whether the project remains notifiable or moves into the ordinary building application procedure.
- 6
Wait for the decision and link the workflowfor notifiable systems, the local building authority informs the client, the Solothurn building insurer and, if needed, further bodies such as the fire brigade. Only then should installation window, scaffolding, grid connection and commissioning be coordinated bindingly.
Checklist
Questions to settle before the quote.
- 30 days before construction starts: submit the notification form, building description, site plan and facade plan in full
- Classify pitched roof, flat roof or facade under Art. 32a or Art. 32abis RPV
- Check protected cases: old town of Solothurn or Olten, Balsthal village core, Jura protection zone and cultural monument
- From 30 kWp, account for fire brigade plan requirements and grid operator clarification before filing
FAQ
Common questions on this topic.
Sources
Official sources & references.
The responsible authorities are decisive. Always verify binding details – amounts, deadlines and conditions – for your specific property against the current status of the respective authority.
- Notification form for solar systems on roofs and facadesCanton Solothurn, Department of Construction and Justice
- Guide to notification and permit procedures for solar systemsEnergy Switzerland / Swiss Federal Office of Energy SFOE
- Building law for solar systemsSwissolar
- Spatial Planning Act Art. 18aSwiss Confederation (Fedlex)
- Spatial Planning Ordinance Art. 32aSwiss Confederation (Fedlex)