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1925 Masonry Slab porch over crawl
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[#1] Posted: 04/03/2012 - 2:28:40 PM		Reply with Quote
Looked at a house with a masonry slab deck for the porch and space below that was connected to the basement. Outside there was some cracking in the deck that seemed more recent than not. The cracks ran from front to back. Told the client I needed to see what made up the supporting structure before I could comment. Expected to see angle iron lintels or I-beams underneath but it was a little different.



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Had good access underneath and found the following structure. Terracotta block that seamed to be supported by some type of reinforced masonry lintel. At first I assumed the steel angle was encased in the masonry and the fact that there weren't any blowouts in the masonry from the steel expanding/rotting was a good thing. Moving down finally found a few "ribs" with blowouts that I helped to fall away and could see some rusting steel inside but it didn't look like angle, I-beam or even rebar. Did find a couple that have some pretty good rot but only a couple out of 25 or so. Found one that the masonry never fully covered the bottom of the steel and it was in very good condition as it was able to dry. It looked like smooth pipe or something, not at all what I was expecting. The TerraCotta block was laid in between the ribs like decking that the slab was formed on top of. I could see up through many of the gaps between the block and and they weren't filled or connected at all, just a platform for the pour.




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There wasn't any sagging but the cracks on the top side with a slight bounce tell me the reinforcing steel is starting to allow more flex than desirable. I told them flat out that this is not something I see on any regular basis and it was different enough from anything I've ever seen that they should find someone familiar with repairing this type of structure to look at it closer. They also asked about sealing the top against water and I told them, the right product, applied the right way could help & the wrong product could make it go ten times faster.
So, anyone familiar with this, have anything to add?
Kyle Kubs
Benchmark Home Inspection Services
New Jersey NJ
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1925 Masonry Slab porch over crawl
 [#2] Posted: 04/03/2012 - 4:08:05 PM		Reply with Quote
If you go to http://historicbldgs.com/terra_cotta.htm , you'll see a diagram of a cross section of that type of floor construction. It's rather common, being about 35-40% of the structural terra cotta floor structures I see. The other 60-65% are constructed like the second floor illustration.

The repair to the rusted steel reinforcement would be the same as with steel-reinforced concrete - that was just recently discussed here.
Bill Kibbel, Historic & Commercial Building Inspections - Old House Resources
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1925 Masonry Slab porch over crawl
 [#3] Posted: 04/03/2012 - 4:41:36 PM		Reply with Quote
Those photos remind me of the ceiling of the basement of a friend's masonry house in Germany.

ONE TEAM - ONE FIGHT!!!

Mike
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1925 Masonry Slab porch over crawl
 [#4] Posted: 04/03/2012 - 5:05:05 PM		Reply with Quote
Quote: Originally posted by Bill Kibbel

If you go to http://historicbldgs.com/terra_cotta.htm , you'll see a diagram of a cross section of that type of floor construction. It's rather common, being about 35-40% of the structural terra cotta floor structures I see. The other 60-65% are constructed like the second floor illustration.

The repair to the rusted steel reinforcement would be the same as with steel-reinforced concrete - that was just recently discussed here.


Ah, so the ribs between the Terra Cotta are actually part of the slab that is poured on top of them... Thanks Bill, the cross section is just what I needed. Just couldn't get it in my head while I was looking up at it.

So the steel is just smooth round bars, no texture?
Know any good masons in North Jersey/Morris County that would know how to deal with this without making a mess of it? I know they're going to ask sooner or later.
Kyle Kubs
Benchmark Home Inspection Services
New Jersey NJ
   
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