Rust stains on concrete/concrete block foundation walls

Cause

Poor quality concrete absorbing water that rusts the reinforcing, which in turns causes the concrete to spall or crack, allowing in more water 

Repair

  • or small areas of concrete damage, (150–200 mm2 maximum), remove enough concrete to expose steel that has no rust; sand to remove rust from the affected reinforcing; prime reinforcing with zinc-rich primer and a metal primer; repair the hole with a sand-cement plaster
  • for larger areas of damage or where little or no reinforcing remains, obtain advice from a chartered professional engineer on repair options

Cause

The reinforcing was installed too close to the outer surface of the concrete

Repair

  • for small areas of concrete damage, (150–200 mm2 maximum), remove enough concrete to expose steel that has no rust; sand to remove rust from the affected reinforcing; prime reinforcing with zinc-rich primer and a metal primer; repair the hole with a sand-cement plaster
  • for larger areas of damage or where little or no reinforcing remains, obtain advice from a chartered professional engineer on repair options

Cause

The building is close to the sea and the concrete is of poorer quality

Repair

  • for small areas of concrete damage, (150–200 mm2 maximum), remove enough concrete to expose steel that has no rust; sand to remove rust from the affected reinforcing; prime reinforcing with zinc-rich primer and a metal primer; repair the hole with a sand-cement plaster
  • for larger areas of damage or where little or no reinforcing remains, obtain advice from a chartered professional engineer on repair options

Cause

The concrete is low strength

Repair

  • for small areas of concrete damage, (150–200 mm2 maximum), remove enough concrete to expose steel that has no rust; sand to remove rust from the affected reinforcing; prime reinforcing with zinc-rich primer and a metal primer; repair the hole with a sand-cement plaster
  • for larger areas of damage or where little or no reinforcing remains, obtain advice from a chartered professional engineer on repair options

Cause

Moisture is rising up from the ground  

Repair

  • for small areas of concrete damage, (150–200 mm2 maximum), remove enough concrete to expose steel that has no rust; sand to remove rust from the affected reinforcing; prime reinforcing with zinc-rich primer and a metal primer; repair the hole with a sand-cement plaster
  • for larger areas of damage or where little or no reinforcing remains, obtain advice from a chartered professional engineer on repair options