built on sand

built on sand

Founded or based on something unstable. Likened to building a physical structure on sand, which is not a suitable building surface. A relationship based entirely on physical attraction is built on sand and won't last long.
See also: built, on, sand
Farlex Dictionary of Idioms.

built on sand

without secure foundations; liable to collapse.
This phrase comes from the biblical parable contrasting the wise man who built his house on rock with the fool who built his on sand (Matthew 7:24–7).
See also: built, on, sand
Farlex Partner Idioms Dictionary
See also:
  • age out
  • appropriate for
  • at face value
  • leap of faith
  • take a leap of faith
  • take at face value
  • take somebody/something at face value
  • take (someone or something) at face value
  • at face value, take
  • judge on its own merits