Yurt Truss Design Withstands Heavy Snows

One of the concerns that we had when we manufactured our yurt was that the winter snow load might be too stressful for the design if the roof. In our part of the continent, we get a fair amount of snow and lake effect snow (120 cm per winter, or 47.5 inches). While this is…

One of the concerns that we had when we manufactured our yurt was that the winter snow load might be too stressful for the design if the roof. In our part of the continent, we get a fair amount of snow and lake effect snow (120 cm per winter, or 47.5 inches). While this is less than the mountainous areas or the eastern seaboard often gets, our snow stays from November until late April.

The roof trusses are designed with two-by-fours installed 24 inches on center at the wall top plate, merging to 1.5 inches at the apex of the yurt dome. Most of the conventional, commercial yurts have a similar truss distribution, and claim that they are sufficiently solid to withstand normal snow loads. However, those manufacturers also offer wind and heavy snow load reinforcement options. Our design has an additional drawback: it is designed with a 28 degree slope, instead of the 40-45 degree slope that is needed to ensure that snow slides off the roof.

In order to distribute the weight of the snow, we installed collar ties at the seven-foot point on each truss (our yurt has a 28-foot diameter), with hurricane ties at the wall plates. To ensure lateral and diagonal stability, we used a 3/8 inch aircraft cable, adjustable through use of a turnbuckle, looped through the ends of each truss. Three by six inch reinforcing plates are affixed within two inches of the top and bottom of each joined wall section.

During the fierce winds that we encountered in late October, there was absolutely no movement of the yurt, providing us with some sense of security that the structure was sound. However, lateral wind is not comparable to vertical pressure of weight, so we have had to wait until the snow arrived to test our design.

As of January 26, we have received 10 centimetres more than the entire seasonal average of snow for our area, so measuring the impact of the snow load for a typical season is possible.

Not only has the roof assembly withstood the entire load, but it has not sagged more than 1 centimetre (1/2 inch), yet the snow depth is almost 8 inches on the lower third of the roof. To further test the strength and stability of the trusses, I climbed on the roof and put my entire weight on the mid-point between collar tie and wall plates, and collar tie and dome. No sag was noticed.

Given the additional reinforcing measures that we incorporated into the design, this durability is to be expected. However, it is welcome to see that theory and practice meet, when it comes to the strength of our design. Consequently, I have no hesitation in recommending a similar layout if you are contemplating construction of your own yurt.