Integrated Buildings & Structures

I am working on a project with an existing building that is 50'-0" wide, is a gable roof with a 6:12 roof slope.  At the center of the roof there is an additional gable roof that extends 6'-0" tall.  Essentially this is a 12'-0" wide gable roof over the peak of the lower roof.  We are adding a new taller structure adjacent to this existing building creating a valley to trap snow between the new building and existing double gable roof.  I calculated the roof drift for the windward and leeward snow drifts but am worried this does not properly account for the valley being created.  Are there additional provisions to be taken when a structure is essentially trapped on all sides by taller structures?

Christopher, in situations like this a standard windward/leeward drift check often isn't enough.
When a new taller structure creates a narrow valley next to an existing roof, it typically acts as a snow-trap, so you should also consider a valley / unbalanced drift case in addition to the regular drifts.

In practice the safest approach is to treat the area between the two roofs as a separate drift load case with a larger effective drift height and width, since snow tends to accumulate more aggressively when it's confined on both sides.

It's a common issue with additions to existing buildings - we usually check windward, leeward and a "captured snow" case as separate load scenarios.

If you can share the height difference and the horizontal gap, I can sketch what that load case might look like.

I am working on a project with an existing building that is 50'-0" wide, is a gable roof with a 6:12 roof slope.  At the center of the roof there is an additional gable roof that extends 6'-0" tall.  Essentially this is a 12'-0" wide gable roof over the peak of the lower roof.  We are adding a new taller structure adjacent to this existing building creating a valley to trap snow between the new building and existing double gable roof.  I calculated the roof drift for the windward and leeward snow drifts but am worried this does not properly account for the valley being created.  Are there additional provisions to be taken when a structure is essentially trapped on all sides by taller structures?

Christopher, in situations like this a standard windward/leeward drift check often isn't enough.
When a new taller structure creates a narrow valley next to an existing roof, it typically acts as a snow-trap, so you should also consider a valley / unbalanced drift case in addition to the regular drifts.

In practice the safest approach is to treat the area between the two roofs as a separate drift load case with a larger effective drift height and width, since snow tends to accumulate more aggressively when it's confined on both sides.

It's a common issue with additions to existing buildings - we usually check windward, leeward and a "captured snow" case as separate load scenarios.

If you can share the height difference and the horizontal gap, I can sketch what that load case might look like.

I am working on a project with an existing building that is 50'-0" wide, is a gable roof with a 6:12 roof slope.  At the center of the roof there is an additional gable roof that extends 6'-0" tall.  Essentially this is a 12'-0" wide gable roof over the peak of the lower roof.  We are adding a new taller structure adjacent to this existing building creating a valley to trap snow between the new building and existing double gable roof.  I calculated the roof drift for the windward and leeward snow drifts but am worried this does not properly account for the valley being created.  Are there additional provisions to be taken when a structure is essentially trapped on all sides by taller structures?

Christopher, in situations like this a standard windward/leeward drift check often isn't enough.
When a new taller structure creates a narrow valley next to an existing roof, it typically acts as a snow-trap, so you should also consider a valley / unbalanced drift case in addition to the regular drifts.

In practice the safest approach is to treat the area between the two roofs as a separate drift load case with a larger effective drift height and width, since snow tends to accumulate more aggressively when it's confined on both sides.

It's a common issue with additions to existing buildings - we usually check windward, leeward and a "captured snow" case as separate load scenarios.

If you can share the height difference and the horizontal gap, I can sketch what that load case might look like.

I am working on a project with an existing building that is 50'-0" wide, is a gable roof with a 6:12 roof slope.  At the center of the roof there is an additional gable roof that extends 6'-0" tall.  Essentially this is a 12'-0" wide gable roof over the peak of the lower roof.  We are adding a new taller structure adjacent to this existing building creating a valley to trap snow between the new building and existing double gable roof.  I calculated the roof drift for the windward and leeward snow drifts but am worried this does not properly account for the valley being created.  Are there additional provisions to be taken when a structure is essentially trapped on all sides by taller structures?