Stone veneer – surface damage or deterioration

Cause

Air-borne pollution, dust or dirt combined with rain causing acid attack on the stone – particularly susceptible are limestone such as Oamaru stone

Repair

  • if damage is severe or the appearance is unacceptable, contact the stone supplier for advice. Restoration of acid-damaged stone surfaces is possible but is best done by experts
  • be aware that many stone veneers are porous, and preventing damage or staining in the first place is a better idea than trying to clean or repair it after it has happened
  • house and gutter design and maintenance must ensure that there are no localised high-level flows of rainwater being chanelled down any stone veneer surface. Over time this can result in damage or staining that can be impossible to clean away
  • stone veneer surfaces should be washed once a year with water and mild detergent using a sponge or soft-bristled brush. A low-pressure garden hose can remove any detergent residue. Don't use chemicals, abrasive cleaners, hard brushes or high-pressure water blasters as they can potentially damage the stone surface
  • stone suppliers often recommend sealing of stone veneer, especially in coastal and geothermal areas. Sealing can help prevent stone discolouration and make for easier cleaning. Always ask the stone supplier for advice before buying and applying a sealant, and if possible test on an inconspicuous area of the wall first. As with most coatings, stone sealers need to be reapplied from time to time – approximately every 7–12 years is common

Cause

Oxidation of impurities in the stone

Repair

  • as for the first repair above