SWINE&U

By Diane DeWitte

If your cubic foot of snow weighs 11 pounds and you have 2 feet of snow on the roof, then you have about 22 psf of snow load on your roof. This method is based on the idea that the snow on the roof is similar to the snow on the ground and that the snow is evenly distributed on the roof. Use caution to avoid falls if you attempt to climb on a roof by using a fall arrest harness and the buddy system.

The excessive amount of ice and snow this past month has livestock owners concerned about snow load on farm building roofs. The design roof snow load for residential buildings in Minnesota is set by state statutes and is 42 pounds per square foot (psf) in northern Minnesota and 35 psf in southern Minnesota. However, many agricultural buildings are built using a 20 psf snow load which would be expected to handle six feet of dry, fluffy snow or one foot of wet, heavy snow.

Estimating the weight of snow and ice on a roof is difficult because snow density can range from 3 pounds per cubic foot for light, fluffy snow to 21 pounds per cubic foot for wet, heavy snow. Ice density is around 57 pounds per cubic foot. One way to estimate snow load on a roof is to go to an area on the ground nearby the shed or barn. Collect and weigh 1 cubic foot of snow (1 foot high x 1 foot wide x 1 foot long). Then estimate or measure snow depth on the roof.

Do you know the snow load capacity of your barn or shed? Snow load capacity is determined by the truss capabilities. Building manufacturers should supply truss certificates as they erect the building.

Shelterbelts

Janni suggests the installation of snow fences and or tree shelterbelts upwind of farmsteads and agricultural buildings as additional ways to prevent excess snow buildup on building roofs.

Proper snow fence design and location is important for protecting a building or farmstead. Some building roofs have failed in the past because the buildings were located too close to shelterbelts or windbreaks, which resulted in large snow drifts on top of these buildings.

Remember when placing a 50 percent solid snow fence or tree windbreak that snow will be deposited downwind a distance of up to 10 times the shelter belt or snow fence height. An 85 percent solid fence deposits the snow within a distance of about four times the fence height. Porous snow fences distribute the snow more evenly and give better protection downwind than a solid fence.

Leaving an area for snow to accumulate is very important when locating a machine shed or livestock building downwind from a shelterbelt. If the building is too close, it will be within this snow drop area. If too far from the windbreak, it will be outside of the wind “protection” zone.

Moving snow around the farmstead

After a winter of heavy snow and ice, livestock owners should consider where the snowmelt will go and how it could make farm operations difficult in the spring. Janni emphasizes that early snowmelt and spring rains can run across frozen ground, gather in low spots and create flooded areas. Melting snow can flood buildings, feed and bedding storage areas in low areas, which can damage feeds, bedding or equipment. Feedlot runoff needs to be managed properly to prevent contaminating surface waters. It is also important to prevent snowmelt from entering in-ground manure storage pits or basins.

When moving snow, producers must plan for spring thaw. Plow or scrape snow off to the side of outdoor exercise lots, feeding areas and heavy traffic lanes. Avoid pushing uphill of outdoor lots, feeding areas and traffic lanes. This will reduce snowmelt that is in — or drains through — the lot or feeding area. Avoid removing manure or wasted feed with the snow unless it will be land applied properly to cropland. Carefully consider where you place snow when you move it around the farm. Locate piles so snowmelt will drain away from animal lots or traffic lanes rather than through them. Also, ensure pump-out covers on deep manure pits are properly seated so snow and roof runoff do not drain into the pit. Adding snowmelt and rain runoff to a manure storage facility reduces manure storage capacity and adds to land application costs.

In the spring, take a good look at the overall farmstead drainage pattern. If other parts of your property drain through the animal yards, feed storage areas, or high traffic areas, regrade the slope or add shallow diversion ditches so runoff water flows around the areas you want to protect.

On some farms, water runs off the barn roof into animal lots. A shallow trench or ditch beneath the overhang can help direct this water out of the yard. Better yet, install gutters and downspouts that empty away from the animal lot. Also, grade the ground around farm buildings to slope away from the building. This helps move snowmelt and rain runoff away from the building and its contents.

Another long-term solution is to avoid placing buildings, feed and bedding storage in low areas. And grade animal yards and the farmstead to provide continuous drainage away from the animals, feed storage, and high traffic areas. A 4 to 6 percent slope is recommended.

Consider building conditions

Snap, crackle pop! A sound you want to hear when eating cereal, but not from your buildings in the winter. Signs of building failure (or damage) include walls bulging at the top from failing knee braces, sagging roof lines, doors or windows that no longer open, physical sounds of cracking and popping, and roof collapse.

If there are indications of building damage or failure, do not climb onto the roof or enter the building. One way to remove snow from a roof is to physically shovel off the snow. There are numerous human safety concerns with this, including falling off the roof. One should use ladders, safety ropes and the buddy system. Also watch out for power lines and take other necessary precautions that may include hiring a professional, if possible.

For more information on managing snow loads on barn and shed roofs, and handling snow around the farm, visit the University of Minnesota Extension website at https://extension. umn.edu/farm-safety

Diane DeWitte is an Extension Educator specializing in swine for the University of Minnesota Extension. Her e-mail address is stouf002@umn. edu