Subfloor – damp stains on underside of flooring

Cause

Leaking water or waste pipe 

Repair

  • identify the source and location of the leak. Make a permanent repair, or call a licensed or certifying plumber to make permanent repair. Work on waste pipes and drains must by law be carried out by a licensed or certifying plumber.

  • establish whether the leak is likely to be a one-off problem or stems from old deteriorated pipework/drains or a design or materials fault that may recur. If the latter, discuss potential long-term solutions with a licensed or certifying plumber or NZIBS building surveyor

  • ensure that the floor dries out completely. Check for damage – part of the flooring may require replacement in extreme cases.

Cause

Overflow or leak from wet area fixtures such as bath, shower, handbasin, dishwasher, clothes washer, hot water cylinder

Repair

  • identify the source and location of the leak. Make a permanent repair, or call a licensed or certifying plumber to make permanent repair. Work on waste pipes must by law be carried out by a licensed or certifying plumber

  • if the fixture or appliance is very old and a permanent repair is difficult, consider replacement

  • ensure that the floor dries out completely. Check for damage – part of the floor may require replacement in extreme cases.

Cause

Inadequately waterproofed tiling in wet area such as no waterproofing membrane under tiles 

Repair

  • the only successful long-term solution will be to remove the tiles, repair any damage to substrates or floor then carefully apply/install new waterproofing and retile. See the Level pages on wet area flooring and floor finishes and waterproofing tiled showers

  • ensure that the floor dries out completely before this work is done, and check for damage – part of the floor may require replacement in extreme cases.