Ridge height — calculation of the permitted building height
What is the ridge height? - The definition
Die Firsthöhe describes the vertical height from the ground to the highest edge of a building, the so-called First. The ridge is the point at which the roof surfaces of a gable roof or a comparable roof meet. The ridge height is particularly relevant for construction projects, as it serves as a yardstick for the maximum permitted building height. It is only measured for roofs with two rising roof surfaces. Roofs without such roof shapes, such as flat roofs, have no ridge height; this is generally referred to as building height.
How do you measure the ridge height?
In order to maintain a uniform appearance in residential areas, cantons and municipalities set the allowable ridge height for various building zones. The measurement is carried out from the ground (usually the lowest point of the property or the top of the road) to the highest point of the roof. This does not include roof structures such as antennas or chimneys.
note: On hillsides, the center of the property often serves as a reference point. Different regulations can be found in the municipal building and zoning regulations (BZO). A look at the building and zoning regulations can help to ensure that measurements comply with local regulations.
Building height with different roof shapes
Determining the height of the building depends on the shape of the roof:
- flat roof: The height is measured up to the highest edge of the roof.
- pent roof: Here, measurements are taken up to the highest edge of the roof surface.
- gable roof: The measurement is carried out up to the ridge point where the two roof surfaces meet.
- hipped roof and tent roof: The measurement extends to the tip or highest cut edge of the roof surfaces.
- arched roof and Barrel roof: Measurement is carried out up to the highest point of the curve.
What are eaves and eaves height?
The opposite of the first is the eaves — the lowest edge of the roof where rainwater drains into the gutter. Die Traufhöhe is the height from ground to eaves and describes the distance from a defined point on the ground to the eaves edge. Roof structures such as dormers are not counted as eave height.
Ridge height requirements
In Switzerland, construction height is regulated by cantonal and municipal building laws. To ensure consistent definitions across the country, the Intercantonal agreement on the harmonization of construction concepts (IVHB) introduced. To date, there have been accession decisions in 18 cantons: Aargau, Appenzell-Innerrhoden, Bern, Basel-Landschaft, Freiburg, Grisons, Jura, Lucerne, Neuenburg, Nidwalden, Obwalden, Schaffhausen, Solothurn, Schwyz, Thurgau, Uri, Valais and Zug (https://ivhb.ch/, as of 2024) .The permitted ridge heights and building heights vary from region to region and are defined in the building and zoning regulations (BZO) of the respective municipalities for the various building zones. For example, the City of Zurich's BZO regulates the maximum building heights and supplements them with specific regulations from the municipalities. The Planning and Construction Acts (PBG) contain general provisions on ridge height.
tip: Anyone planning a new building or would like to upgrade an existing building should contact the responsible municipality at an early stage about the applicable height regulations. Violations of the permitted ridge or eave height mean that the building application cannot be approved.
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