Bracing of existing stone facade during interior renovation

[Ben29]

I am seeking advice on whether or not I should take this on. I have done bracing for tilt-wall panels in the past, so I understand the basics.

I was asked to engineer a bracing and shoring scheme to brace existing stone facade (about 8 inch thick) during renovation of existing (small) building. This is a wood-framed structure with basement. Built circa 1900. Stone facade was added circa 1950's (assumed).

The new owner plans to:
1)demo the existing 1st and 2nd floor.
2)Infill the basement.
3)Pour SOG at 1st floor elevation.
4)Keep the attic and roof framing.
5)Install new wall framing (and/or structural steel framing) as needed to support the existing attic flooring and existing stone facade.

My proposal states that they must hire a 3rd party engineer to design the facade bracing. The architect came back and told me the owner wouldn't want to do that. And he asked if I could do the bracing myself.

 

[JAE]

Putting aside the technical approach to bracing the facade, it seems that if you did it you'd be confusing the line between your agreement with the owner and the work of the contractor. I presume you'd be contracted directly with the owner and never with the contractor, but the line between design and construction seems lost here.

 

[PEinc]

Call PlanB Engineering in the Philadelphia area.

https://planbengineering.com/shoring-and-bracing/

http://www.PeirceEngineering.com

 

[Enable]

So they want to keep the facade while you demo the inside? Neat little project and shouldn't be too complicated. External retention structures are quite common for historic masonry preservation; though the engineers doing that work around these parts are a bit too cavalier for my taste. Also, here this would usually be part of the contractor's scope as a delegated design item. The reasons for that are generally pretty good:

A) This is a temporary work and cost effectiveness will depend on what tools the contractor has in their arsenal. Which you won't know as the designer. You'll probably spend time designing stuff that the winning contractor will want to change later anyways.

B) Masonry cracking is a real concern and from a liability perspective it makes sense to keep it with the party that will be performing the removals. The means and methods of those removals can mess up a perfectly good retention design.

That said, you can certainly design it as the EOR. I've seen shoring designs from EOR's before as a bidding contractor. However, if this is your first time doing it I'd probably suggest keeping it as a delegated design item. It seems like the owner is under the impression that they have to retain an engineer themselves, which obviously they don't have to do. I'd sell it as cheaper by going delegated design and better for the owner's cash flow, which is not untrue.

 

[bookowski]

My $0.02. Have them get a proposal from the firm mentioned by PEInc. That proposal will be way more than your fee (based on my experience). Then offer to do it for 75% of that. This stuff is not rocket science, mostly just risk tolerance. Unless there's some particular constraint you should be able to accomplish most of this with sequencing, something like: 1) open demo the middle 1/4th of the ground floor and infill from there to 2ft below the ground, 2) demo balance of ground and infill, 3) brace walls parallel to joists at 2nd floor, 4) demo and reframe the middle 1/3 of 2nd floor, 5) demo and reframe the outer 1/3rds of 2nd. The bracing of the parallel to joist walls can be pretty lowbrow. One option is adding some corner bracing above the floor level to tie the parallel wall to the perp wall. Alternately you can brace the parallel wall to the floor several feet back from the wall, allowing them to remove the 1st two parallel joists, then reframe those first two with permanent anchorage to the wall. You can do it, easy money and you understand the building more than anyone else will anyway.

 

[Enable]

bookowski: I generally agree that it can make financial sense for an EOR to take on this responsibility, and if I was the EOR, I certainly would. However, historic masonry retention is not something you want to do for the first time without having seen how others do it in the area. If Ben29 has been involved in other projects where similar work was performed then it makes sense. But taking this one without seeing what others do in the area first is asking for issues either for technical reasons (don't know what you don't know) or due to contractor's in the area having a strong preference for a particular type of system (very common with temp works) but designing something different. Heritage projects are also kinda funky because we arn't allowed (generally) to put holes in them to keep them up!

 

[Ben29]

Thank you all. I responded to the architect with the points made by Enable. We will go forward with the delegated design option.