Snow and wind | Onduline lightweight roofing

UK wind uplift and snow loading

If erecting a new building in a location likely to be subjected to high wind and snow loadings always seek professional advice from the buildings supplier to investigate if any structural variations or strengthening is required to counter increased roof loadings.
On existing buildings the maintenance and structural integrity of the building should be surveyed and upgraded as required and if necessary again seek professional advice (Architects, Surveyors, Civil Engineers and your local Building Control Department.

Identifying risk factors:

The factors that should be considered in the roofs design are as follows:

Building size and configuration: The span of the roof, its design layout, roof slope and height; The ‘dead’ loading applied typically comprising of the weight of individual structural elements, and the ‘live’ loadings applied to the roof such as wind and snow forces acting upon it.
Location: in respect to predicted wind speeds m/s
Exposure: whether located in an urban location or out in the country
Altitude of site: The wind speed and snow loadings applied to a roof are likely to be significantly increased the higher the buildings elevation is above sea level.
Distance from sea: Higher wind speed is generally experienced in coastal areas as the force of the wind is not dissipated by the lands topography, trees, buildings etc.
Parapets and roof obstructions: Against which air turbulence can be created; or snow drift against increasing the point weight loadings on a roof structure appreciably.

Buildings in the UK are designed in compliance with the British Standards and Codes of Practice which take into account site location however, your buildings designer or supplier should be consulted should you require confirmation of your buildings design conformity. Building Control Departments can also provide information in this regard.

Wind uplift loadings

Tested to wind speeds

The Onduline products fixing specification’s in relation to wind loadings have proved themselves more than capable in dealing with even UK extreme gales and weather events being tested to withstand wind speeds of up to 120mph (192kph - 53.6 m/s); therefore the risk as can be seen from the photographs below is more to the integrity of a building and its roof design; in both these cases the Onduline sheets have not parted company from the roof structure; rather it is the buildings structures which have failed resulting in their damage beyond economical repair.

ROOF DESIGN IN EXPOSED UK AREAS OF HIGH WIND AND SNOW LOADINGS

Leading weather performance

Onduline roof coverings weathering and service performance worldwide confirms Onduline roofing products are both durable and resilient resulting in brand leading weathering performance.

Structural faults in the roof and building design are normally associated with roofing failures.

Correct installation

For example: A timber frame building which has been designed for use in a typical low elevation sheltered location and which under normal conditions will provide years of trouble free service; However, the same building erected on an exposed elevated coastal site and being subject to much higher wind and snow loadings without upgrading the building’s structural design is likely to be at risk of structural failure; which can be both dangerous and expensive to resolve far exceeding the cost of upgrading the original roof structure.

Causes of roof failure during gales and snow loading is the failure to fix the product correctly in accordance manufacturers fixing instructions. We therefore advise that the fixing of your Onduline roofing product is checked to ensure it is in compliance with the relevant fixing instructions.

Snow loadings

Design considerations

Generally, the dominant load factor requiring design consideration on a roof following a fall of snow is the additional weight it imparts on the roof structure. This load combined with wind loading, ice melt and the increased weight of compacted snow on a roof structure an d the effect of prolonged exposure to below freezing temperatures on roof structures must be reflected in the design strength requirement of a building’s roof section.

Onduline Lightweight roofing systems

Onduline has a range of lightweight roofing solutions that are suitable for extreme weather conditions. We have two options below that would be ideal for your DIY project, whether a garden shed, summer house, children's playhouse or any other type of outbuilding. Find out more below.