Vejledning om udnyttelige tagetager – Danish Building Guidance on Usable Attics
The Vejledning om udnyttelige tagetager is an administrative guidance document issued by the Danish Transport, Building and Housing Authority (Trafik-, Bygge- og Boligstyrelsen). Published in July 2018, this document provides the regulatory framework for defining and calculating usable attic space within the context of the Danish Building Regulations (Bygningsreglementet). It serves as a secondary administrative provision under the broader scope of the Danish Building Act (Byggeloven).
The guidance establishes specific criteria for what constitutes a usable attic and how these areas affect the calculation of the plot ratio (bebyggelsesprocenten). It details the historical shifts in regulation, specifically the transition from the rules prior to January 1, 1976, to the current standards established in the Bygningsreglementet of 1977. The document outlines technical thresholds, structural definitions—such as the distinction between truss rafters and collar tie rafters—and the legal implications of changing an attic's status from usable to unusable.
This technical document is used to determine when a building permit is required for changes in use and how local plans (lokalplaner) or town planning ordinances (byplanvedtægter) may override current standard calculation methods based on their original adoption dates.
Definition of Usable Attics
A usable attic is defined based on the possibility of utilizing the space without requiring significant interventions in the load-bearing structures. The guidance provides technical examples of what constitutes such an intervention.
- Significant Structural Intervention: An example is the replacement of truss rafters (gitterspær) with collar tie rafters (hanebåndsspær).
- Usability Status: Since January 1, 1976, usable attics must be included in the plot ratio calculation regardless of whether they are actually utilized.
Area Calculation Standards
The method for calculating the floor area of a usable attic depends on the height above the finished floor and the intersection with the roof's exterior.
- Current Standard: The area is measured in a horizontal plane 1.5 meters above the finished floor, extending to the intersection with the outer side of the roof cladding.
- Historical 1976 Rule: For a brief period in 1976, the measurement plane was set at 1.0 meter above the finished floor.
- Pre-1976 Rules: Prior to January 1, 1976, only habitable rooms, bathrooms, and their access routes were included; secondary or utility spaces were excluded.
Local Plans and Planning Ordinances
Property-specific regulations can supersede general building regulations if the property is governed by a local plan or town planning ordinance.
- Applicable Rules: The calculation rules in force at the time the local plan or ordinance was adopted must be used to calculate the floor area.
- Legal Precedence: Local planning foundations dictate the specific calculation method for plot ratios even if they differ from current 1.5-meter standards.
Conversion and Change of Use
The guidance details the process for reclassifying an attic from usable to unusable and the requirements for a building permit when changing the attic's function.
- Structural Reclassification: A usable attic can become unusable if the structural and static conditions are altered, such as installing truss rafters during a renovation.
- Plot Ratio Manipulation: Structural changes made solely to alter the basis for plot ratio calculations do not automatically result in the attic being classified as unusable.
- Change of Use Permits: Converting a storage room (pulterrum) in a usable attic into a living space is considered a significant change of use under Byggeloven § 2, stk. 2, litra c, requiring a formal building permit.
Frequently Asked Questions
At what height is attic area measured for the plot ratio?
Under current rules effective since February 1, 1977, the area is measured in a horizontal plane 1.5 meters above the finished floor.
What structural change makes an attic 'unusable' according to the guidance?
An attic is considered unusable if the structural conditions prevent its use without significant intervention, such as the presence of truss rafters (gitterspær).
Does the actual use of the attic affect its inclusion in the plot ratio?
No, since January 1, 1976, all usable attics must be included in the plot ratio calculation regardless of whether they are actually put to use.
Is a building permit required to turn an attic storage room into a bedroom?
Yes, changing the use from a storage room to a habitable room is a significant change of use under Section 2 of the Building Act and requires a building permit.
Which calculation rules apply if a property is under an old local plan?
The calculation rules that were valid at the time the specific local plan or town planning ordinance was adopted must be applied.
How were attic areas calculated before January 1976?
Only habitable rooms, bathrooms, and their access ways were included in the area calculation, while utility and secondary spaces were excluded.
