Building Occupancy Category

[KevinChez]

I have been designing a number of backyard pavilions and pergola type structures (independent of the main house structure) and have always used an Occupancy Category of II. Wind load usually controls for these structures so I've considered using Cat I since there will most likely not be in use during a major wind, snow or seismic event? My concern is a plan examiner reviewing my drawings taking objection and then me having to redo my analysis and calculations. In California I need to submit a calculation package with each submission so it can be tedious and time consuming.

I wanted to get an opinion on using Cat I vs Cat II for an accessory residential building structure. thank you.

 

[Lomarandil]

For a private structure (not a public gathering space) I think there's justification for Occ Cat I based on limited impact to human life and the low probability of occupancy during a design event. I think that's strengthened if there is a more suitable shelter (house) nearby, and if the pavilion/pergola doesn't provide much protection from the elements (e.g. open walls).

I've previously argued the same for parks (like a picnic shelter), but other members here have pointed out that may not be as good an argument if the occupants don't have somewhere else nearby to go in a storm.

 

[JLNJ]

No way I'd use Catergory I for a pavilion. Heck, you can make the argument that people would run toward and seek shelter under a pavilion when a storm whips up. A small pergola, maybe Cat I if I were really trying to sharpen my pencil, but probably Cat II for me anyway.

My feeling is that Category I is for agricultural structures and the like where humans are very unlikely be to at risk.

 

[driftLimiter]

ASCE 7-16 is titled. "Minimum Design Loads and Associated Criteria for Buildings and Other Structures"

Keyword is minimum. If the EOR wants to design for more load then the plan reviewer cannot demand they go lower.

I can't tell if your worried that the reviewer will require Cat I, if so you can always say Okay I will indicate it as Cat I but our design loading is based on Cat II.

I would use Cat II for these all day.

 

[KevinChez]

My concern is using Cat I and having them bump me up to Cat II.

I use Cat II on all my designs and then am liberal with the 1.6 increase for wind and seismic where it applies for wood members and connections.

Thank you!

 

[MotorCity]

I would consider a pergola to be occupied as often as an agricultural bldg....put me in the Risk Cat 1 camp.

That said, if I were nervous about the AHJ calling it a Risk Cat II building and redoing a calc package, I'd err on the conservative side and go the Risk Cat II route. I doubt it will make a significant difference in the size of members or connections.

 

[Aesur]

Kevein - Have you checked if your local SEA chapter has an opinion on this? I have seen opinions be offered before through such organizations which allowed for the use for this in carport structures. Personally I prefer II for the reasons others have stated, people tend to seek shelter during a storm, and often times they seek the closest, which means they will head to said shelter and stay there till the storm calms down to head to the house.