  Understanding the underlying structure of building surfaces like walls and
floors is essential when carrying out building maintenance and modification
work. To facilitate such work, this paper introduces a capacitive sensor-based
technology which can conduct non-destructive evaluation of building surfaces.
The novelty of this sensor is that it can generate a real-time 2D subsurface
image which can be used to understand structure beneath the top surface. Finite
Element Analysis (FEA) simulations are done to understand the best sensor head
configuration that gives optimum results. Hardware and software components are
custom-built to facilitate real-time imaging capability. The sensor is
validated by laboratory tests, which revealed the ability of the proposed
capacitive sensing technology to see through common building materials like
wood and concrete. The 2D image generated by the sensor is found to be useful
in understanding the subsurface structure beneath the top surface.
