Mønehøyde

Mønehøyde (roof ridge height) is the height from the terrain around the building to the intersection between two sloping roof surfaces, that is, to the top of the roof. On a pitched roof, the ridge height is always greater than the eaves height, which is measured to the intersection between the external wall and the roof. The difference depends on the roof pitch and roof shape, and can range from under a metre (a shallow pitched roof) to several metres (a steep gable roof).

The standardisation follows NS 3940 Areal- og volumberegninger av bygninger, while the legal framework sits in plan- og bygningsloven § 29-4 on siting, height and distance to the neighbouring boundary. The general rule in the act is 8 m to the eaves and 9 m to the ridge, unless a zoning plan or municipality plan says otherwise. The guidance to the byggteknisk forskrift TEK17 from Direktoratet for byggkvalitet sets out what counts as finished graded terrain and how the average level is to be calculated when the site is not flat.

Even so, it is the provisions of the zoning plan, not the standard, that govern which measurement method applies to a specific project. The plan can bind the developer (tiltakshaver) to a set contour height (absolute height above sea level), to road level, to quay level or to a specific method. The four most common methods for ridge height:

• From the average level of the finished graded terrain around the building (the standard in NS 3940).
• From the lowest point of the adjoining terrain.
• From the highest point of the adjoining terrain.
• From a fixed reference level, typically road level, street level or quay level (contour height).

On composite roof shapes such as hipped roofs, mansard roofs or shed roofs, a ridge may not exist as a single clear point. The municipality then decides which highest intersection point counts as the ridge. Under TEK17 § 6-2, technical structures on the roof (lift overruns, ventilation plant, stair enclosures) are to be included in the eaves height unless they are set back behind the eaves on the inner side of the roof, which matters a great deal in practice for the development of office buildings and apartment buildings with technical plant on the roof.

Sloping sites are a well known source of error: measurement points on the low side give a taller building than points on the high side, and differing interpretations of what counts as finished graded terrain are among the most common grounds for complaint in building cases. Municipalities therefore usually require survey drawings with a terrain profile and documented measurement points in the application for a framework permit.

Together with eaves height, BYA and UFA, the ridge height governs the volume of the building and is one of the most important density parameters in municipality plans and zoning plans. For developers, the operational question is not only what the act and the plan say, but also which measurement method the plan requires. A contour height gives more predictability than an average level above graded terrain. In Placepoint, you read the applicable plan and its provisions in the property panel.

How this looks in Placepoint

In Placepoint, you find this in the Property panel:

From Placepoint's dictionary: Mønehøyde

More information: Lovdata: plan- og bygningsloven § 29-4, DiBK: TEK17 og veiledning, Standard Norge: NS 3940, Store norske leksikon: mønehøyde

English: Roof ridge height (per Plan- og bygningsloven).

Frequently asked questions

What is mønehøyde?

Mønehøyde is the height from the average level of the finished graded terrain around the building to the top of the roof, that is, the intersection point between two sloping roof surfaces. It is regulated in the plan provisions.

How is mønehøyde regulated?

The municipality plan and the zoning plan often set a maximum permitted ridge height. There are four common measurement methods: from average terrain, from the lowest point, from the highest point or from a fixed level.

What is the difference between mønehøyde and gesimshøyde?

Mønehøyde is the height to the top of the roof. Gesimshøyde (eaves height) is the height to the intersection point between the external wall and the roof surface. On a pitched roof, the ridge height is always higher than the eaves height.

What happens if the terrain slopes?

Measuring the ridge height can be difficult on a sloping site. It is important to use the correct measurement method under the plan provisions, because an error can result in an unlawful building height.

How do I find the maximum mønehøyde for a property?

The ridge height is set out in the provisions of the zoning plan. Placepoint gives you access to the applicable zoning plan, and the specific measurement method has to be read in the text provisions of the plan.