Er din bygning snesikker? – Danish Building Snow Safety and Structural Integrity Guide
The official publication Er din bygning snesikker? was issued by the Danish Erhvervs- og Byggestyrelsen (now part of the Danish Authority for Social Services and Housing) in 2010. This guidance document functions as a technical advisory for property owners to assess the structural safety of buildings under heavy snow loads. It was developed in collaboration with Træinformation, Landbrug og Fødevarer, and Forsikring & Pension following a series of roof collapses during the winter of 2009/2010. The document provides a framework for identifying structural vulnerabilities in commercial and agricultural buildings, such as stables, halls, barns, and machine sheds.
The scope of the document covers two primary construction types: wide buildings with timber trusses (træspær) and buildings with steel frames (stålrammer). It details specific technical requirements and inspection points, including lateral bracing (tværafstivning), diagonal bracing (skråafstivning), and corner reinforcements. The regulatory context is grounded in Byggeloven (the Danish Building Act) and Forsikringsaftaleloven (the Insurance Contracts Act), outlining the legal responsibilities of the building owner regarding maintenance and risk mitigation. Specific thresholds are established for buildings with spans exceeding 15 meters for standard trusses and 12 meters for scissor trusses (saksspær).
This technical reference provides structured criteria for self-inspection and professional assessment. It outlines the specific indicators of structural failure, such as member bowing, missing bracing, or undocumented modifications, which may lead to collapse during significant snow accumulation.
Legal Basis and Owner Responsibility
Under Danish law, the building owner is legally responsible for ensuring that the structure complies with building regulations and remains safe for use. The municipal authorities may intervene if a building does not meet safety standards.
- Byggelovens § 17, stk. 1: Authorizes municipalities to order owners to rectify conditions that do not comply with building legislation.
- Forsikringsaftaleloven § 52: Requires owners to take all possible measures to avert or limit damage. Failure to do so may impact insurance compensation claims.
- Maintenance Obligation: Owners must maintain the structure; if safety is in doubt, a consulting engineer or structural expert should be contacted.
Identification of High-Risk Factors
Certain conditions increase the likelihood of structural failure during snow events. Buildings constructed or modified without proper documentation are at higher risk.
- Pre-1980 Construction: Agricultural and commercial buildings from this era may have significant structural deficiencies.
- Undocumented Modifications: Changes to load-bearing structures that lack technical documentation.
- Neighboring Structures: Low buildings located near taller buildings are prone to increased snow accumulation due to the shelter effect.
- Physical Damage: Visible wear, corrosion, impact damage, or misalignment in the load-bearing members.
Inspection of Timber Truss Structures
The guide specifies five critical checkpoints for buildings with timber trusses, particularly those wider than 15 meters or scissor trusses wider than 12 meters.
- Truss Alignment: Trusses must be straight. S-shaped bowing or lateral deviation exceeding the thickness of the member (typically 45-65 mm) indicates a risk of collapse.
- Member Bracing: Long web members must have lateral bracing at points marked TVÆRAFSTIVNING.
- Diagonal Stability: Lateral braces must be secured with diagonal bracing to a distribution lath. These are required at each end of the building and every 10-15 meters in long buildings.
- Collar Beam Bracing: Large trusses with collar beams (hanebånd) must be braced every 15-20 meters to prevent lateral bowing.
- Truss Girders: Buildings wider than 15 meters (12 meters for scissor trusses) require truss girders (gitterbjælker) between truss heads every 15-20 meters.
Inspection of Steel Frame Buildings
Steel frames must be inspected for verticality and the presence of specific stabilizing components that prevent twisting or buckling under load.
- Twisting and Alignment: Visible twisting or misalignment in the steel frames is a sign of potential failure. Max allowable twisting is often very low.
- Corner Joints: Frame corners must be reinforced with welded web plates (kropplader). Missing plates in profiles taller than 22 cm can lead to collapse.
- Purlin Bracing: Purlins must be secured to the steel frame with bracing brackets (afstivningsbeslag) and web plates to prevent frame rotation.
- Wind Bracing: Buildings must have wind bracing (vindkryds) in both the roof and walls, ideally located at both ends of the building.
Frequently Asked Questions
Which buildings are at the highest risk of snow collapse according to Erhvervs- og Byggestyrelsen?
Buildings with timber trusses spanning more than 15 meters and older steel frame constructions (specifically those over 10 years old or pre-1980) are at the highest risk.
What is the maximum allowable bowing for a timber truss member?
A timber member or truss should generally not bow more than its own thickness, which is typically between 45 and 65 millimeters.
How often should diagonal bracing be installed in long buildings?
Diagonal bracing should be installed at both ends of the building and then at intervals of every 10 to 15 meters.
Are steel frames under 22 cm height required to have web plates?
According to the guide, steel profiles with a height of 22 centimeters or less do not necessarily require web plates at the bracing brackets.
What is the legal consequence of neglecting building maintenance in Denmark?
Under Byggelovens § 17, the municipality can order the owner to fix the building, and under Forsikringsaftaleloven § 52, neglecting safety can lead to the loss of insurance coverage.
What should be done if a building is suspected of being unsafe?
The use of the building should be restricted or avoided, snow should be removed from the roof, and a consulting engineer or truss supplier should be contacted for a structural assessment.
