It is generally accepted that steel buildings, when properly constructed, are more efficient and better value than those built using traditional methods. In colder parts of the country, however, where heavy snowfalls are expected in winter, special provisions are necessary to ensure that prefabricated steel buildings can deal effectively with the conditions.
Properly designed buildings that are correctly installed by a professional and experienced steel structure company can easily outperform buildings that are constructed from other materials.
However, a failure to account for conditions, particularly for likely snow loads, can lead to damage to the structure’s roof, a threat to the structural integrity of the building and, at worst, even roof collapse that can result in injury and death.
Being aware of the dangers and preparing for them is essential to preserve the condition of the building.
Complying with Cold Region Codes
The American Society of Civil Engineers (ASCE) sets out guidelines for cold weather steel building design, which cover the differences from standard building design for warmer regions. The main element is ASCE 7-16 that is for areas that experience heavy snow loads, freezing temperatures, ice accumulation and strong winds.
Specific requirements for cold weather steel building design include:
- Handling heavy snow loads, which might be only 20 pounds per square foot (PSF) for standard commercial buildings but need to be higher in colder regions — typically 40+ PSF in the mountains of Colorado, 50+ PSF in Minnesota and 60+ PSF in the coastal areas of Maine.
Snow load limits indicate the maximum weight for a roof and must not be exceeded, otherwise damage may result, so it is important that you take account of local conditions. Steel buildings are, however, able to withstand heavy snow loads due to optimized roof pitch design, clear span construction and engineered truss systems.
- Correct insulation so that ice dams do not form on the roof due to snow melting and then refreezing at lower levels. A minimum R value of 19 is recommended for moderate climates, increasing to 30+ in colder regions such as Montana and to 38+ in extreme northern regions.
- Foundation frost protection to prevent heave and thermal bridging across concrete floor slabs. This is achieved by extending footings beneath the frost line — 36 inches in moderate regions and up to 60 inches further north.
Other ASCE provisions deal with unheated buildings and roof slopes, types and overhangs. The main focus is on keeping the building dry and able to withstand the effects of extreme weather.
Design Considerations to Deal with Snow Loads
The starting point is a snow load calculation, which depends on local area conditions — region, exposure, elevation and recent history. Strong winds can cause serious accumulations of snow while the duration and intensity of the snow will determine the ground levels. The Metal Building Manufacturers’ Association (MBMA) sets the codes and the ones to be used are selected by the local building department or permit office.
Specific design features may need to be incorporated in high risk areas:
- A steep roof pitch that helps snow slide off naturally — a 1:12 pitch is the minimum requirement while 2:12 or even 3:12 may be needed in some areas. A steep pitch will shed snow gradually and avoid damage and injury caused by large snow slides.
- Snow guards may be needed to protect people and property from large and unexpected snow slides from roofs.
- Stronger engineered trusses combined with additional support beams and columns will help to distribute snow weight across the roof.
- Avoid unnecessary obstructions and roof irregularities that can cause snow accumulations and unbalanced loads. Flat roofs cause a balanced load but this can be significant.
- Use high strength steel profiles and ensure the building is properly anchored since heavy snow can often be accompanied by high winds. Galvanized steel will give extra protection against snow and moisture.
- Adequate insulation of the roof will prevent the snow melting and then forming ice dams when it refreezes at lower levels. This can cause damage to ceilings and roof structures so the exterior surface of the roof needs to be kept cold. Vapor barriers should be combined with proper insulation to prevent moisture entering the system and condensing on cold surfaces.
- The roof needs to be properly sealed, especially at openings, surface penetrations, roof to wall transitions and connections to the foundations.
Protecting your Steel Building from Snow Damage
When heavy snow does occur, it is important it does not accumulate above recommended levels. It should therefore be cleared periodically to reduce the overall load and prevent the formation of ice dams.
To avoid problems, you should also undertake regular maintenance:
- Check the roof for signs of damage that needs to be repaired before it gets worse.
- Make sure the drainage system is working correctly so water does not accumulate.
- Look for cracks or gaps in walls and roofs, sealing them so that moisture does not damage the structure or inhibit the effectiveness of insulation.
Always undertake a thorough inspection before winter starts and fix any problems. Early remedial action will ensure problems do not get worse and become more costly, and will extend the life of the building.
If you are in a cold region that experiences frequent heavy snowfall, you need to ensure that your steel building has all the necessary design features. Cold climate buildings are significantly different to standard ones for warmer climates and it is crucial you do not underestimate the serious effects that extreme weather and heavy snow can bring since these can affect the integrity of the building and the safety of those using it.
At Atlantic Steel Structures, we have long experience of developing steel buildings of various types and for all climates. We can create exactly the building you need and ensure it remains weather-proof and durable throughout its long life. Complete our enquiry form or give us a call to find out more.
