Early 20th century Row House Sally Ports

[MacGruber22]

Subject: The masonry walls which form sally ports between row homes...The masonry is built to arch up to the shared masonry party wall above, right? I just can't see how the 2nd floor wood joists span across the sally port to support the masonry walls above. Someone is trying to tell me differently, and I am doubting myself. The sally port clear width is usually 24" - seems reasonable to be able to corbel the masonry above.

Sketch attached to help out.

 

[bookowski]

That is a really nice sketch!

Not sure what you mean about the joists carrying the wall. The wall is self supporting through arching (and/or possibly a permanent or temporary form lintel built into the arch). The joists is pocketed in there, but the wall is supporting the joist rather than the other way around.

 

[msquared48]

I cannot see the wood joists ever supporting the shared wall above. They are usually ledgered to the side of the wall on a corbel, or inset into the brick wall itself. In either case, the joists do not support the wall above, except laterally as a reaction point for the floor diaphragm.

Mike McCann, PE, SE (WA)

 

[BAretired]

I agree that the arching effect of the masonry over the Sally Port (that's a new term for me) carries the wall above. The arch thrust must be carried by internal friction, not something I would like to rely upon.


BA

 

[MacGruber22]

Thanks, bookowski! It is literally a sketch, not to be part of CD's.

Sorry for the confusion, though. My question is more general about this type of construction, and the sketch is for a specific court case, deposition, arbitration, etc. etc. (not sure what is going to happen yet). In this case, the residence to the right has been razed some time ago. Based on the dimensions taken, I agree there is no way that it couldn't be a corbeled arch-like system. But, I was curious if anyone has seen joist framing cantilevering to pick up the party wall. The idea sounds like a very poor construction technique (load-carrying, deterioration, etc.), but I am always surprised by what I find all the time!

 

[MacGruber22]

BA: the good thing is that there are intermediate buttresses (masonry piers), installed when the adjoining building was demolished. I was aware there are many terms for those little through-ways, but I have always referred to them as such because they usually have security features when they lead to private rear yards; the definition of a sally port, in the more modern sense, always seemed to fit these things. (doesn't hurt that I giggle when I hear or say the word!)

 

[racookpe1978]

Could the arch be "resisting" falling down (because the other house/wall/mass was removed after original construction) simply because it is "held up" by "friction" + paint + hopes and prayers + good luck?

 

[MacGruber22]

In this case, I doubt it. Generally, I feel good about the arching because of the added buttresses - no signs of distress and it has been in this condition for 20-years. I have not been retained to perform a structural analysis, so I don't want to open up a can of worms...scope creep.

 

[BAretired]

The lateral force required at the ends of the arch is about 0.2 P where P is the centrally applied concentrated load (see attached link). If P is in the order of 900 #/' then a force of about 180 #/' is required. Friction might work, but it seems a bit dicey to me. As for paint, hope, prayers and good luck...I would rely mostly on the paint if there is any.

BA

 

[msquared48]

I can see the arching effect, but I can also see a deep beam effect.

Is, or are there any horizontal steel ties? Or...do the joists continue through the wall with metal connecting straps? If there is either, then there is more of a beam effect and less of the arch effect.

Mike McCann, PE, SE (WA)

 

[MacGruber22]

There is a thick parging on every surface - that takes care of 0.1P!

I have no idea about the detailing performed on that wall when the adjacent building was razed. Finishes interfere with checking for a positive joist-wall connection at the arch. I wish I had this book on hand (

http://books.google.com/books/about/Structural_Analysis_of_Historic_Building.html?id=zCCY0-iPgRMC).

A colleague of mine owns it and I looked at it a few years ago, and was very impressed by the quantity of "historic" construction details.

 

[msquared48]

If the adjacent building has been razed, then the joists do not serve as a tie. Is it possible to observe the possible connection at the razed portion and extrapolate from there?

Mike McCann, PE, SE (WA)

 

[MacGruber22]

No, it isn't observable. That would require select removal of the parging (which is part of the lawsuit). Again, I am not worried about it because of the buttresses. Plus, portland cement parging is so brittle, right? - there would have been cracks years ago if that wall was laterally-compromised, IMO. The parging is in good condition, no bulging/delamination, etc.