Exam 2 case study question

Hi @coachadamcoers can you explain more in depth the difference between types of plants desired being a feasibility issue rather than sq/ft of the roof in this question?

I sort of get that it’s a better answer, but doesn’t the sq/ft of the roof also affect the cost/feasibility of the green roof for the building?

The entire facility requires a new flat roof system. The owner has asked the architect to consider a vegetated roofing system.

Which of the following items should the architect consider when determining the feasibility of a vegetated roofing system? Check the four that apply.

Building square footage

Incorrect. The building square footage will impact the roofing design but is not a factor to determine the feasibility of the system.

Climate at the location of the facility

Correct. The climate of the facility will affect the type of plantings that can be used.

Height of building

Incorrect. The height of the building is not a factor when determining the feasibility of vegetated roof system.

Type of existing roofing system

Correct. The vegetated roof system may be able to utilize components of the existing roofing system in its design.

Type of plantings desired

Correct. The type of plantings desired will be the determining factor for the category of vegetative roof system.

Load-bearing capacity of the roof deck

Correct. The load-bearing capacity of the roofing system should be reviewed and may need to be reinforced to hold the desired category of vegetative roof system.

Reference: Architectural Graphic Standards


In this case, it does appear as though they are talking about installing a vegetated roof on an existing roof. So with that, the feasibility they are referring to would be structural feasibility vs a cost feasibility.

The reason that the types of plants would be a greater consideration over the square footage because you would be looking at the structural capacity of the existing deck and roof system. For example, an extensive green roof which is mostly grasses mosses and small plantings like that is going to have a substantially smaller impact on the structural system compared to an intensive green roof system which would include trees, shrubs and additional human loading to regularly required maintenance.

Once you have determined if the structure can support the green roof, the next step is when the square footage will come into consideration as to whether or not the client can afford it. But for this particular question, you’re looking for structural feasibilty and not affordability. if that makes sense.

Hopefully this helps!

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