Strange central air duct

I inspected a 1952 model home this week with a slab foundation, almost unheard of in Okla in 1952. What was even more strange was it had central supply air duct beneath the slab with a horizontal furnace in the attic split system. I am checking the register for rust and holes in the metal thinking surely the metal is gone. I see dirt in the ducts confirming my belief that the metal is gone. I dig into the dirt and find concrete beneath the dirt ok so someone has patched the holes with concrete. I run my sewer cam down the duct and see concrete all the way down the duct much further than someone can reach from the register patching holes. Low and behold the ducts were completely constructed with concrete and wire mesh like one would for stucco. In my 40 years in the HVAC business I had never seen concrete ducts before. Now I have;-):wink:

Was it a perimeter duct system. There is one neighborhood in Tulsa that has concrete perimeter ducts.

Yes it was

If we are talking about the same neighborhood, it was one of the first places centeral heat and air was residentially installed. There are a few ducts in the neighborhood that were built with cardboard surrounded by concrete, most of those have not faired well… most of the houses still have the 3 phase power from original construction. Cool neighborhood.

What area of T town are we talking about I do very little residential in Tulsa mostly commercial

Lortondale. Basically, east side at 26th and Yale.