Pedestrian Walkway Considerations

[jl3]

Hi All,

We are proposing a small pedestrian bridge/walkway (~170 SF) between two buildings connecting the 4th floors of each as our client has space in each building; building owners are separate, but they have both agreed to the bridge in concept. We're using IBC 2021, one building is type IIB, other is type IB, distance between buildings is about 16 feet, both buildings fully sprinklered and both business occupancy.

Our main concern here is avoiding any fire rating of the exterior of either building - the main code section we're following is 3104.5.2 since we're over the 10ft separation requirement and below the 55ft roof height (bridge will be sprinklered, walls/doors separating); there's also 3202.3.4 that will just need to be subject to AHJ approval. On a side note, the building that is type IB construction has 1 HR rating for the wall facing the opposing building on the interior side per 705.5 since the FSD is over 10ft (10'-2"), as this building was constructed after the type IIB building.

The bridge is about 17ft in length and about 9ft in width, but is angled about 24 deg off perpendicular, so it doesn't go straight across. A question was brought up recently on whether or not there's any issue here with the bridge being canted, specifically in relation to adjacent exterior windows being closer in proximity to the bridge than if it was just a straight, perpendicular shot across buildings.

Is there anything else we may be overlooking here?

 

[walker.t]

Is there anything else we may be overlooking here?

My thoughts run to things other than the building code.

IBC 3201 is in regards to encroachments into the public right-of-way - so you have some sort of alley between the buildings and not just a side yard setback?

Assuming you do have an alley, you probably want to talk to your zoning department to find out what they are going to require for an encroachment agreement over the public right-of-way. Something like this bridge will be considered a major encroachment (versus a de minimis encroachment) which may need to be approved by your planning board or maybe even city council. That could easily add 90 days to the process to talk with staff, submit the application, and get on the agenda. I wouldn’t be surprised if they say there’s a risk to the municipality (which there is) and deny the request.

If you have a setback between the buildings you’ll need a variance from the zoning department.

The property owners need to get together with their lawyers to figure out an easement that protects their rights to the bridge including the fact that the other building is holding up the other side of the bridge. You say the bridge will be sprinklered - into which existing sprinkler system are you going to tie the bridge’s sprinklers? And who is going to pay the electric bill?

A structural engineer will need to determine if the buildings can support the new loads imposed by the bridge.

I have no idea what the building department will think when they consider what might happen if one building were to collapse in a fire. How much will the bridge pull on the other building? It will rip a hole in the building that didn’t collapse as it hinges down and impacts the building, then cause damage to the lower floors as the bridge falls to the ground.

 

[Yankee Chronicler]

IBC section 3104 is the appropriate code reference. Unless both buildings are on the same lot, such a bridge is considered to be separate from both buildings -- it's a thing unto itself.

Looking at section 3104.5.2 and the two conditions it addresses, it seems to me that you satisfy the criteria for not needing to rate the exterior walls of the two buildings at the bridge.

 

[Penguin87]

^ Agreed, its a separate structure that will require everything to be fire rated. You will need an architect and structural engineer to assist. And lawyers.

If you are serious, I would recommend scheduling a pre-app meeting with the local AHJ to figure out what you will need to do to get this permitted. Does city zoning even allow it?

 

[Fred_F]

^ Agreed, its a separate structure that will require everything to be fire rated. You will need an architect and structural engineer to assist. And lawyers.

If you are serious, I would recommend scheduling a pre-app meeting with the local AHJ to figure out what you will need to do to get this permitted. Does city zoning even allow it?

Yeah, I think getting a lawyer is a great idea and maybe the best decision since doing this project may have some legal implications. Good luck!

 

[Yankee Chronicler]

^ Agreed, its a separate structure that will require everything to be fire rated. You will need an architect and structural engineer to assist. And lawyers.

If you are serious, I would recommend scheduling a pre-app meeting with the local AHJ to figure out what you will need to do to get this permitted. Does city zoning even allow it?

Why does it need "everything" to be rated?

Look again at IBC 3014.