Snow drift from new building

[Heldbaum]

Hello folks, I know there are existing threads about this topic but I couldn't find anything that would answer my concern. We are doing a new 9-story building in place of existing 2story at 25'x100' lot. There is an adjacent 3story building, +70 years old minimum probably. My question is if I should be concerned about the snow drift since the existing building has ( like most of the buildings) a parapet wall. I am aware of the fact that old codes did not account for any snow drift but my question is - if there is a parapet wall the condition of additional snow accumulated on the roof already exists so there will be a very small difference between the snow accumulations due to parapet wall and snow drift coming from the new building..What do you think ? Both roofs are flat.

Thank you as always in advance!

 

[dik]

thread507-440604

Depending on the jurisdiction... you should be concerned.

Dik

 

[JAE]

Yes - refer to the recent thread that dik posted.

Also - you would want to calculate the "existing" snow drift based on the existing parapet wall - then compare that to the proposed "new" condition with your 9 story building.

If the snow drifting is essentially the same or less then you should be OK to proceed with the new building.
However, if, as is more likely probable, your new 9 story building creates more drift load than before, then in my view you have an obligation to notify the existing building owner and proceed from there with respect to upgrading the existing building.

I won't dive into the weeds of who pays for what (see the other thread) but you at the least have the duty to notify the adjacent building owner.

Also keep in mind that the IBC has a provision for some allowed overstress in gravity supporting elements (5%).
See the existing building section in the back of the IBC.



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[BAretired]

I think that, without doing a lot of calculations, you should advise your client that his 9 story building may affect the snow load on the adjacent building and hence, the adequacy of the existing roof. Your drawings should include a site plan indicating which existing buildings may be affected.

The neighbor may prefer to retain his own engineer to determine whether or not remedial measures are required on his building. It is likely that some discussions will take place among interested parties regarding who pays for what.

BA

 

[WARose]

If you affect the adjacent building.....very likely you are responsible or will be found to be responsible. (Unless there is something in the code that specifically says otherwise.)

When stuff like this goes to court.....the outcome is unpredictable.....therefore your approach needs to be: let's never let this become a litigated issue.

 

[BAretired]

I don't see how the Engineer of Record can prevent it becoming a litigated issue. That would be something for the two owners to address. The EOR must advise his client and the authority having jurisdiction of a situation which could affect the safety of an adjacent building. What happens next is out of his (the EOR's) hands.

BA

 

[WARose]

I don't see how the Engineer of Record can prevent it becoming a litigated issue.

For one thing (if the clearances allow it) put some sort of overhang/canopy (off of the taller building) that would cut off/pick up any drift.

Another might be changing the layout of the building (in plan view).

That would be something for the two owners to address. The EOR must advise his client and the authority having jurisdiction of a situation which could affect the safety of an adjacent building. What happens next is out of his (the EOR's) hands.

I wouldn't be 100% sure about that. Me personally, I'd be hesitant to issue IFC drawings until it was resolved to everyone's satisfaction. (Including a indemnification agreement for the EOR & his company.) Putting a drawing out there that is a potential danger to life and limb could come back to bite you. You can bet if there is a lawsuit, there will be a complaint filed with the PE board well before that.

If the owner of the adjacent building dragged his feet on modifying the short building and disaster strikes.....and all you have is a bunch of verbal assurances that it was going to be fixed (even if someone else is paying for it).....the situation could get dicey. (And costly regardless of who wins.)

 

[Heldbaum]

Thank you very much for all your input!