Live Load Reduction for a Room Growing Cannabis 5

[Datonedavid]

Hi, Everyone.
I got a client who has a factory who wants to remodel the second floor to grow cannabis.
In terms of Live load I think the description best meets a greenhouse which would would rate it at 125 PSF.
When I asked the client how much their plant weighs(soil,plant,and water combined), the amount of plants in the room, and the area of the room it comes out to 4 PSF.
I spoke with building official and he said that he would entertain a "rational" live load reduction proposal under Section 1607.12.2.1 of the IBC.
But I'm unsure what qualifies as rational approach pertains.
Would love to hear your guys thoughts on what the correct live load should be and reasoning.
Thank you for your time.

 

[phamENG]

When I asked the client how much their plant weighs(soil,plant,and water combined), the amount of plants in the room, and the area of the room it comes out to 4 PSF.

I think you're largely on the wrong track here. Unless they plan to put it all in a big blender, turn into a smoothy, and pour it out to harden on the floor, it's not a very useful number. There will be areas of higher load concentration that need to be accounted for. There's the people doing the work. There's probably machinery of some kind. So if you want to start sharpening your pencil, you need to start mapping out travel routes of carts/pallet jacks, enforce social distancing for the workers to make sure they don't overload the same joist, etc.

It's a greenhouse. Design it as one. You have no control over what they are growing or how they grow it. What's to stop them from doubling or even tripling their production in that space? What happens if their automatic watering system malfunctions and overfills the growing racks, quintupling your live load? There are a lot of variables wrapped up in the development of the live load figures to ensure the building is reliably safe. When you design houses, do you ever try to argue that the average live load in a residential space works out to be about 6psf, so you shouldn't have to use 40psf?

I could get behind using live load reduction, though, given the likely proportion of long term live loading. Your slab/joists will need to take 125psf, but girders and columns could likely be designed for less.

 

[EngDM]

It's a greenhouse. Design it as one.

Agree with everything said above.

 

[Stick.]

Some plants in pots spread across the floor are hardly going to be your only relevant load. For instance, palletized growing medium/soil looks like it could be in the neighborhood of 125 psf (based on some rough napkin math). It would be entirely conceivable for them to store pallets of growing medium in one corner of the facility, and to phamENG's point, you don't know which corner that will be in 10 years.

 

[JAE]

Agree with phamENG totally.
But I might add a few comments.
1. It’s an existing floor. What’s its original design live load? Maybe it’s already 125.

2. If you have a floor that’s close - say 100 psf, then you might have the owner post the live load around the floor with multiple signs stating the capacity you’ve derived. This after sharpening your pencil and having a good feeling that the actual possible live load (plants, storage areas, carts, people, etc) are well under your capacity. At the very least your photos of the posted live load signs prove that you gave them a limit.

 

[bones206]

I did one of these a couple years ago. Didn't even know there was a greenhouse load in the code...

I told the owner I was designing it for 100 psf and posted that limit on the stairs going to the new second floor. Basically treated it like a mezzanine.

 

[JoshPlumSE]

In terms of Live load I think the description best meets a greenhouse which would would rate it at 125 PSF.

It sounds close enough to a greenhouse that it would be hard to justify some other loading. I think the reason why the PSF is so high is because soil weighs a lot. Especially when it's well watered.

 

[XR250]

How does posting the live load accomplish anything? Which employee is qualified to determine if they are exceeding this?

 

[jerseyshore]

I don't see how posting the live load is useful either. A layperson wouldn't even know what the term "live load" means.

Different than a sign that says "max occupancy 50 persons".

If signs were useful wouldn't we be throwing them up on every job?

 

[LittleInch]

Maybe they weigh 300 lbs...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bones206]

Rated load posting is pretty common practice with mezzanines. Same for pedestrian bridges, cranes, hoists, etc.

I recall discussing the weights with the owner, and the equipment was actually pretty lightweight from what I recall. I think the 100 psf I rated it for was maybe on the order of 10x what he showed me for operating weights.

Just did a little googling and came across this case from Oregon:

https://www.portlandoregon.gov/bds/appeals/index.cfm?action=entry&appeal_id=13236.

Appears they allowed 75 psf for a 2nd floor mezzanine at a cannabis facility.

 

[phamENG]

Load rating signs are usually only used in situations where it is reasonable that a responsible person capable of making the determination will be in charge of the space. So you couldn't use it in, say, a conference center with random people milling about, but you could in a warehouse with administrative controls overseen by a manager.

 

[bones206]

I look at it as an extra precaution. If you know there is a possibility of inadvertent overload based on the nature of the facility or structure, load posting is a precautionary measure to alert occupants. It doesn't take the place of doing the proper load analysis and design.

 

[bones206]

It also saves new facility ownership from having to hire an engineer to do a load analysis on an existing mezzanine. If there is a load rating plate affixed, it's more likely to survive over the years than the design drawings.

 

[jerseyshore]

People may put signs on mezzanines (bridges and cranes are totally different IMO), but are they doing it instead of designing something for the code specified loads? I am asking because I've never seen a sign that says max LL on mezzanine 100 psf when by code it should be 125.

I can see you putting a sign up that says 80 psf (for office) and "No storage" or something like that just to reinforce the allowed use.

I can't imagine if there's a failure at a house you can go "I put a sign that says max 6 psf LL not my fault" and get away with it.

 

[phamENG]

Right - it's usually used for existing structures. Building has been there for 80 years, they want to use it for some purpose that would normally be 125psf but 80 years ago it just 'got built' and now it can only safely support 64psf but we only need 50psf. Something like that.

It's not usually allowed I've never seen it used for new construction.

 

[dauwerda]

Load rating signs are required by OSHA for any elevated storage (new or existing):

1926.250(a)(2)(ii)
Employers shall conspicuously post maximum safe load limits of floors within buildings and structures, in pounds per square foot, in all storage areas, except when the storage area is on a floor or slab on grade. Posting is not required for storage areas in all single-family residential structures and wood-framed multi-family residential structures.

 

[milkshakelake]

I have one client that really cares about the posted live load rating. I did evaluation of a distillery for checking their live load capacity signs. The employees were playing music, dancing, probably drinking on the job (that's my mental image of everyone working at a whiskey plant), and definitely don't know what a live load is. But the manager was hyper aware of the value, checking all the equipment to make sure it was within the limit. Probably for liability reasons. They renew the evaluation every few years, and check all their new forklifts, equipment, and keg stacks with an engineer (signed and sealed) to make sure it's within the limit.

 

[Tomfh]

Max load signs are common on repurposed structures. If your actual loading is well below the actual capacity it’s a reasonable approach.

 

[Eng16080]

How does posting the live load accomplish anything? Which employee is qualified to determine if they are exceeding this?

I agree it's unlikely that an employee or owner will be able to assess the actual live load on a floor.

Of course, in the (normal) case where the load is not posted, this will most likely still be true, and additionally they'll likely have no idea what the design live load of the floor actually is. At least if it's posted, the information is readily available, so it could be used.

It would be interesting to see where the liability would land if the greenhouse floor was loaded well past the 125 psf design load and resulted in damage. Is the owner/employees supposed to know this limit, or are they simply allowed to use the space as a greenhouse (which is rather vague)?

EDIT: I see that dauwerda perhaps answered my question, per the OSHA requirement.