Unknown nomenclature on existing 2

[EngDM]

Hey all,

I'm working on a very old existing building, and there is a portion of the main floor slab that has notation I am not familiar with. I'm hoping someone here can point me in the right direction. See below:


I think I get the bottom 3 lines, it's just the 12+2 that is giving me grief.

There's notes on the drawings that show "pre-cast cellular slab" but I'm not familiar with this. A quick google only returns pictures of hollowcore, but the photos of this area show 5" concrete bridging joists, so I don't think it is hollowcore.

 

[ANE91]

12-inch slab + 2-inch topping? Like how PCI notates.

 

[EngDM]

12-inch slab + 2-inch topping? Like how PCI notates.

Would a 12in slab have 5" bridging joists @ 25" on center though? Seems really heavy.

The slab on the other side of the beam that this slab frames into is only a 5", and the difference between underside of slab on either side of the beam is only 3". That's why I thought 2" slab, since 5-2 = 3.

This building is also OLD, like pre 1921. Here is an expanded screenshot of the slab callup in this area.

 

[RattlinBog]

Is it some sort of station / location?

 

[EngDM]

Is it some sort of station / location?

How do you mean?

There are other areas of the building that also indicate 12+2, so it's not identifying any unique location. There are other spots that are 8+2.

 

[RattlinBog]

There are other areas of the building that also indicate 12+2...

Okay, that rules out a station. It was just a guess. Beats me then!

 

[EngDM]

Okay, that rules out a station. It was just a guess. Beats me then!

Appreciate the idea though.

I agree with the concensus that the 2 is 2" topping. Which makes sense because the notes have pre-cast as an option, which usually has a topping. To further support this, there is no +2 on the slabs that are identified as R/C which I presume means reinforced concrete (cast-in-place).

 

[JAE]

The 12 + 2 is usually an indication of a concrete cast-in-place joist system where the 12" represents the vertical depth of the pan forms and the 2 is the slab thickness over the pan forms. Very common in older structures.

Usually the framing plans would then show the rib withs and the pan widths

 

[ANE91]

Would a 12in slab have 5" bridging joists @ 25" on center though? Seems really heavy.

The slab on the other side of the beam that this slab frames into is only a 5", and the difference between underside of slab on either side of the beam is only 3". That's why I thought 2" slab, since 5-2 = 3.

This building is also OLD, like pre 1921. Here is an expanded screenshot of the slab callup in this area.

View attachment 5780

Saw your edit.

Precast cellular makes it a lot less heavy than you’d think. And those 5” joists are likely there for stiffness, not strength.

 

[JAE]

Here's a sketch...

 

[EngDM]

Saw your edit.

Precast cellular makes it a lot less heavy than you’d think. And those 5” joists are likely there for stiffness, not strength.

I can't find a manufacturer from back then that shows pre-cast cellular, and I looked at that Antiquated Structures PDF by M. Stuart to no avail. The slab almost reads as if it is Floretyle (which is what they used in an addition to the building), but there is no metal form underneath.

 

[EngDM]

Here's a sketch...

Shoot this is probably it, but the plans dont indicate a spacing. Of course my area of work is the only spot on the drawings with a mistake, because the 8+2 areas are shown as below, and show the 5" joists at 25" O.C.

So 5" is the width of the joist, as shown by your 4-6".

 

[JAE]

If the plan shows 5" joists at 25" o.c. then the pans are 20" wide pans spaced to provide a 5" wide rib.

 

[JAE]

Sometimes just going to the building and measuring the rib spacing and widths is necessary.

 

[EngDM]

If the plan shows 5" joists at 25" o.c. then the pans are 20" wide pans spaced to provide a 5" wide rib.

Yes, they just didn't provide this information in my one area of work (if you compare the 8 + 2 screenshot to the 12 + 2 screenshot).

The site is not overly accessible at the moment so I'm trying to get by without site measuring and getting the contractor to confirm once they can access the area.