Composite steel-concrete floors
The principle
Section titled “The principle”The profiled steel sheet does two jobs:
- formwork for the pour — no propped shuttering is needed over the whole area,
- reinforcement in the finished structure — the sheet works on the tension side.
The concrete provides the compression zone, the steel the tension. That is the classic composite logic.
The Lewis dovetail decking solution
Section titled “The Lewis dovetail decking solution”Where sound insulation demands are higher — an apartment-building floor, for example — a floor on Lewis dovetail steel decking is a proven solution.
The sheet counts as the bottom reinforcement, so a load-bearing, well insulating floor can be built at a thin depth: roughly 30 mm of concrete.
The concrete is separated from the steel sections with rubber strips, a cheap solution because it is not needed over the full area.
What it gives the build-up
Section titled “What it gives the build-up”The most important thing for sound insulation and the feel of the vibration. Impact sound insulation · Floor vibration.
A rigid, flat surface
Section titled “A rigid, flat surface”Favourable for rigid finishes such as ceramic tiling.
Diaphragm action
Section titled “Diaphragm action”The stiffness of the floor plane also plays a part in distributing horizontal loads. Sheathing diaphragm.
A shallow structural depth
Section titled “A shallow structural depth”A gain in ceiling height or overall height.
What has to be solved
Section titled “What has to be solved”The load
Section titled “The load”A wet build-up adds load that the structure has to carry — which feeds back into sizing the joists.
The separation
Section titled “The separation”Resilient separation is needed between the concrete and the steel sections to reduce sound transmission.
Moisture
Section titled “Moisture”The pour brings moisture into the structure, which has to dry before the build-up is closed.
Corrosion
Section titled “Corrosion”Contact between steel and fresh concrete is a chemical question too. Where steel meets concrete.
The point
Section titled “The point”A composite floor is most valuable where mass is needed: for sound insulation and the feel of the vibration. At a thin depth it gives what a dry build-up cannot.