What is a fontanel in a concrete floor?
In a concrete floor, a fontanel is a relatively small, often somewhat thinner panel section that can easily be removed in the future. This allows a pipe or chimney flue, for example, to be run through the floor slab later without breaking open the whole floor.
How does a fontanel work?
The name derives from the fontanel, the soft spot on a baby’s skull where the cranial bones have not yet fused. Like that soft spot, the fontanel in the floor forms a deliberately weakened zone:
- The panel is made thinner at that spot than the surrounding floor.
- The reinforcement is limited or interrupted there, so the section can be broken out later.
- The rest of the floor retains its full load-bearing capacity.
In this way, it is already determined during casting where an opening can easily be made in the future.
Application
Fontanels are used when, during construction, it is not yet certain exactly where pipes, a flue, or a stairwell should be located, but the option needs to be kept open. Instead of making an opening straight away, a spot is reserved with a fontanel. When the penetration is actually needed, the contractor can remove the thin section relatively easily and finish the opening neatly.
Related terms
- Concrete floor
- Opening (recess)
- Roof opening
- Expansion joint
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.