PV solar carport dimensions/classification

[fish1534]

I am trying to layout my PV solar array canopy over an existing parking lot of 750 parking spaces and would like canopy length to exceed 150'. This topic has been discussed several times on this forum and canopies with photovoltaic arrays are best classified as occupancy use U, carports. Section 503.1 from code is below and has a special exception that if I meet certain dimension requirements the canopy does not add to the building height or floor area. How does this apply to at grade parking? I am occupancy U with Type I construction, so my building size is unlimited, and height is also not an issue (5 stories). Are these dimensional requirements only for open/closed parking garages, occupancy type S? Fig. 5-1 looks an awful lot like a surface lot. Can I just run my 40-foot-wide canopy for 200 feet? What am I missing? What do I gain or why am I required to follow these design criteria?

503.1 General.
Unless otherwise specifically modified in Chapter 4 and this chapter, building height, number of stories and building area shall not exceed the limits specified in Sections 504 and 506 based on the type of construction as determined by Section 602 and the occupancies as determined by Section 302 except as modified hereafter. Building height, number of stories and building area provisions shall be applied independently. For the purposes of determining area limitations and type of construction, each portion of a building separated by one or more firewalls complying with Section 706 shall be considered a separate building.

Exceptions:
3. Other than structural requirements, solar photovoltaic panels supported by a structure over parking stalls shall not constitute additional story or additional floor area and may exceed the height limit as specified in exception 2 (above) when the following conditions are met (see Figure 5-1):

1. The area within the perimeter of the solar photovoltaic array has a maximum rectangular dimension of 40 feet by 150 feet.
2. The distance between solar photovoltaic array structures is a minimum of 10 feet clear.
3. The driveway aisle separating solar photovoltaic array structures has a minimum of 25 feet clear.
4. Solar photovoltaic array structure is used only for parking purposes with no storage.
5. Completely open on all sides (other than necessary structural supports) with no interior partitions.

 

[TheCommish]

Look to the definition of building v Structure, I would suggest you don't have a building rather a structure, such as a cell or radio tower short and wide. The design should take into account, wind, gravity, and impact loads.

Possible some consideration of solar installation in fire codes and manufacturers listing

 

[Yankee Chronicler]

I am trying to layout my PV solar array canopy over an existing parking lot of 750 parking spaces and would like canopy length to exceed 150'. This topic has been discussed several times on this forum and canopies with photovoltaic arrays are best classified as occupancy use U, carports. Section 503.1 from code is below and has a special exception that if I meet certain dimension requirements the canopy does not add to the building height or floor area. How does this apply to at grade parking? I am occupancy U with Type I construction, ...

I have seen solar arrays erected over shopping mall parking lots. The structural components were unprotected steel, which would be construction type II-B, not type I. Load bearing components in type I construction have to provide a fire-resistance rating. How are you protecting the structure?

 

[fish1534]

Thank you for the replies so far. I have borrowed Fig. 5-1 of the applicable code from another forum member so my question is easier to understand at first glance. Also, I am the civil engineer (non-structural), so I am not concerned with the actual design of the structure. In our practice civil is generally the first designer because there are more site-specific issue with zoning, lot coverage, permeability, stormwater, accessibility, etc. so we do the site plan and site the structure.

Since the structure acts as shade and rain protection, I am certain it is classified as a carport which is a building with Occupancy U and not a structure. I want to know why there is a code benefit to using the design standards in the code exception below. If I am type IIB, NS construction with a U classification, my carport is allowed to be two stories tall, with a maximum height of 55', and a maximum allowable area of 8,500sf (if S2 NS, I'm allowed more square footage). For two standard parking stalls back-to-back being 40' wide, this means my carport can 212.5' long. What section of code am I missing that would limit this to under 150', that it is a benefit for me to take advantage of section 503.1? There must be some catch in code for them to include this exception! I don't want to tell the client I can cover his entire 200' parking row without a 10' break at 150' and then eat crow and have the structural engineer need a redesign!

Once again, love the form and plan to contribute after I figure this one out!

 

[steveray]

I know there were some proposals in 2024 (or maybe 2027 Group A) to pin down how to deal with these....Assumedly in favor of the PV industry...I don't remember the outcome..

 

[e hilton]

, my carport is allowed to be two stories tall, with a maximum height of 55',

To me, saying 2 stories tall implies a floor of some type separating the stories. Is that correct? Or is it just limiting the height? I would not consider a 2-floor structure to be a carport, it’s more of a parking garage or parking deck.

 

[Yankee Chronicler]

An array of solar panels may provide some shade and some weather (rain and snow) protection, but that's not its purpose. The one I am most familiar with, FWIW, has gaps several inches wide between the panels, so as a roof it's pretty leaky. I don't think this falls within the IBC definition of "Building." I think it's a structure.

[A] BUILDING. Any structure utilized or intended for
supporting or sheltering any occupancy.

[A] STRUCTURE. That which is built or constructed

The solar array doesn't support any occupancy, and it doesn't shelter any occupancy because an exterior, on-grade parking lot isn't an occupancy.

 

[fish1534]

To me, saying 2 stories tall implies a floor of some type separating the stories. Is that correct? Or is it just limiting the height? I would not consider a 2-floor structure to be a carport, it’s more of a parking garage or parking deck.

Code limits, height, stories, and floor area based on construction type and occupancy classification. I'm giving the generic limitiations in code based on occupancy type U. Occupancy type U includes:

agricultural buildings
aircraft hangers
barns
carports
communication equipment structures
fences greater than 7 feet
grain silos
livestock shelters
private garages
retaining walls
sheds
stables
tanks
towers

It is pretty absurd for my carport to be 55' high or two stories, but you could see how some of the buildings in this classification such as a grain silo could exceed 55' in height. The reason I list the limitations is to point out how generous the occupancy group really is. Why do I need an exception to this code if I meet special design criteria? There must be a catch that I am missing, or section 503.1 would have never made it into code!

 

[fish1534]

An array of solar panels may provide some shade and some weather (rain and snow) protection, but that's not its purpose. The one I am most familiar with, FWIW, has gaps several inches wide between the panels, so as a roof it's pretty leaky. I don't think this falls within the IBC definition of "Building." I think it's a structure.





The solar array doesn't support any occupancy, and it doesn't shelter any occupancy because an exterior, on-grade parking lot isn't an occupancy.

Thank you; I hear what you are saying, and honestly, I don't know. Building or structure isn't an argument I want to have with a building official. Since type U specifically list carport as a building, I'm not sure how successful I would be claiming that the roof is 95% roof and 5% open, so it isn't a carport. If this covered the drive aisles or was in a farmer's field, I think it would be a structure but because we are choosing to park cars under it, I think it is a hard sell that it isn't a carport. Regardless, I can make it work as a carport. I just don't understand this bit of code and don't want to learn why the max length is 150' instead of 200' feet from a comment back on my plans and the drafting time to redraw it!

 

[fish1534]

I know there were some proposals in 2024 (or maybe 2027 Group A) to pin down how to deal with these....Assumedly in favor of the PV industry...I don't remember the outcome..

I'm new to the job and I am going to be doing a lot of these, so I need to learn this now for the next fifty. Once I figure it out, I will share so the answer is in the forum. I've read several places online that this is a giveaway to the PV industry or 'in their favor' but I'm trying to understand why the PV industry wouldn't deserve it. How come I can build 8,500 sf horse stable but not a 40x200 carport? What is the fire danger from a carport open on all sides in the middle of an enormous parking lot? It seems to be pretty noncombustible and pretty easy to escape!

 

[e hilton]

It seems to be pretty noncombustible

Maybe the way you are designing it, but i can imagine some people trying to build a pretty shaky structure.

 

[fish1534]

Maybe the way you are designing it, but i can imagine some people trying to build a pretty shaky structure.

Thank you for the compliment but I'm not the designer, I get to pass it off to another guy. I design the roads, utilities, stormwater, and unsexy stuff. To cover 750 spaces though is a pretty large structure. For comparison, 750 spaces is every parking space at a Walmart super center. This one is going at a university named after a state. But usually parking structures at universities, airports, etc. are pretty solid.

I'm still hoping on here to find that building official that knows how large you can make one of these things!

 

[steveray]

I'm new to the job and I am going to be doing a lot of these, so I need to learn this now for the next fifty. Once I figure it out, I will share so the answer is in the forum. I've read several places online that this is a giveaway to the PV industry or 'in their favor' but I'm trying to understand why the PV industry wouldn't deserve it. How come I can build 8,500 sf horse stable but not a 40x200 carport? What is the fire danger from a carport open on all sides in the middle of an enormous parking lot? It seems to be pretty noncombustible and pretty easy to escape!

Because a parking garage is a parking garage....

 

[wwhitney]

Since type U specifically list carport as a building, I'm not sure how successful I would be claiming that the roof is 95% roof and 5% open, so it isn't a carport.

Seems like a pretty clear distinction to me, with a carport your car won't get wet from vertical rain; with a solar ground mount array over parking, it will. One provides shelter, one doesn't.

So which one are you building?

Cheers, Wayne

 

[Paul Sweet]

I think the intent of 503.1 exc. 3 is to allow solar canopies to be built on the top level of a multi-story parking garage without them adding to the number of stories or building height.

Since your canopy is at grade and 1 story you are within the height limits of Tables 504.3 & 504.4, so this exception shouldn't apply and the 8500 SF area limit of Table 506.2 should apply.

 

[fish1534]

opy is at grade and 1 story you are within the height limits of Tables 504.3 & 504.4, so this exception shouldn't apply and the 8500 SF area limit of Table 506.2 should apply.

Paul, thank you for your response and I tend to agree with you. Because building code does have many moving parts, before advising a client, I'm always looking for someone that has run into the issue before, the "ask me how I know guy"!