West and East Side Snow Buildup on Greenhouse†
Our new greenhouse is 38′ wide by 96′ long and 21′ high. To prevent collapse from winter snow buildup on the peak we have a center line of posts supporting a ridge pole. A big question I’ve wondered is how much snow buildup would there be to the east and west of the greenhouse down along the foundation where it slides off.
We built the greenhouse up on a wooden foundation to give some room for snow banks to build up along the sides of the arch. I often see these sorts of greenhouses right on the ground, and this one came with steel ground posts to do it that way. We had to order the feet to sit on the foundation separately.
By putting the ribs up on the foundation there is extra room for snow to build up and not press in the greenhouse fabric. This continues to allow the snow to slide off by itself during the winter saving us the effort of having to manually clear the snow.
The foundation varies from 3′ tall at the north west corner to 5′ tall at the south east corner. This is because we had the plateau very carefully bulldozed the to that slope. This allows for drainage. There is also a berm around the foundation to redirect water away from the interior.
The top of the foundation is within an inch or so of perfectly level so that while the land slopes the greenhouse itself is level. That helps with the structural engineering making the building stronger. But, that creates a challenge with the foundation and snow drifts because I could not economically get posts long enough to make the foundation as tall as I wanted. The result is I went with 8′ posts. At the south east corner where the foundation is tallest the 8′ posts are about 3′ into the soil.
So we have a compromise of a foundation not quite as tall as I wanted but the real question is: “is it tall enough?”
The answer based on this year appears to be yes, the foundation is tall enough. It’s plenty tall on the east side and tall enough on the shorter uphill west side.
Much of the snow blows off the greenhouse so it never settles and has a chance to slide down the sides. We get a lot of wind. Even though the greenhouse is built down in a lee of the mountain its plateau does not end up with the deep snows of other places because much of the snow is carried away by the wind. This is an advantage for siting of the greenhouse.
What does settles onto the arch tends to slide right down. The opaque billboard tarp we’re using as a covering this winter is not as slippery as real greenhouse film but it is slippery enough to dump the snow.
The complication with the answer is we didn’t put the tarp on until mid-winter so not all the snow had a chance to be part of an experiment. Had the snow buildup been a problem we would have plowed down the longwise sides of the greenhouse with the tractor to remove snow. So far it has not been an issue. More data next year.
Outdoors: 34°F/24°F Sunny
Tiny Cottage: 66°F/62°F
Daily Spark: Being a farmer and not believing in evolution would be like being a baseball player and not believing in physics. It’s possible but it would be a major league handicap in the big leagues.
†Note that the middle of the photo is missing.