Cinder Concrete Floor Deck
Cinder concrete was an early development in concrete floor construction. It was appeared about one hundred years ago or so, when engineers and builders started combining steel and concrete to frame a floor. It was a method that used a draped steel wire mesh to support a cinder concrete fill. That is, the wire mesh was considered a structural catenary, a series of tiny cables, and the cinder concrete was considered a fill to provide a walking surface and protect the steel wire mesh. The wire mesh acted as rope hammock stretching from one joist or beam to the next. The cinder concrete provided a level walking surface.
This type of floor was often used to frame downtown sidewalks that were cast over basements that extended out under the sidewalks. They were also used to frame residential porch floors.
A problem arises in this type of floor construction when the strands of the steel wire mesh corrode and their ability to provide support is reduced. Fortunately, these types of floors usually exhibit sagging and cracking before they collapse as the strands of the corroded steel wire mesh stretch. This is called a ductile failure. In a ductile failure the structural element exhibits deformation, sagging, and/or stretching that signals danger to a prudent person. If left unheeded, the failure of the floor could be catastrophic.
So, if a cinder concrete floor exhibits more than surface corrosion of the steel wire mesh, sagging, and/or cracking, call a structural engineer, qualified contractor, or someone from the local building department to evaluate it as soon as possible before it develops into a catastrophic collapse.