What Are Other Common Problems with Paint?

Sagging or Running

When you see dripping or drooping look to areas of the paint film, you would have spotted problems where the application of a coat of paint that was too heavy or overloaded. This can be caused by heavy handed paint application, paint thinned too much at time of application, or applied in poor environmental conditions such as too cool or when humidity was too high, applied without primer to a high gloss vertical surface preventing the paint substrate from having the “tooth” necessary for the finish coat to adhere or the painted surface was not clean or properly prepared at the time of application.

Possible Repairs:

  • Always redistribute excessive paint evenly with a brush or a roller.
  • If the paint is dried, sand the uneven area and lightly reapply paint.
  • Sand glossy surface to provide a good surface for the paint to adhere to. 
  • Paint using two light coats instead of one very heavy coat.
  • Do not overload the paint brush. 


Mildew is a fungus feeding and growing on the paint film or caulk and is identifiable by its grey, brown, green or dark black “splotchy” spots and can be caused by a combination of moisture, poor ventilation and lack of direct sunlight, painting over a surface or prior paint film that still had mildew, the use of lower quality paint having inadequate mildewcide and not priming bare wood before painting.

Possible Repairs:

  • Scrub with a trisodium phosphate cleaning solution or a household bleach solution of 1 part bleach to 3 parts water.
  • Let the solution set on the cleaned are for 10-15 minutes.
  • Rinse with clean water.
  • Wash the area with a detergent solution and rinse again.
  • Let completely dry and paint with a high quality latex house paint.

Rust Discolouration

This problem is characterized by rust colored reddish-brown to black stains on the paint surface and can be caused by non-corrosion resistant nails were used instead of galvanized zinc plated or stainless steel nails. Steel nails coming into contact with the air, popping from surface, excessive weathering or sanding has worn away galvanized coating on nail heads and tannic acid from moist wood (e.g., oak) has reacted with steel nails creating a black stain could also be factors for rust discolouration.

Possible Repairs:

  • Replace steel nails with galvanized or stainless steel nails.
  • If rusted nails can\’t be removed then remove rust by sanding nail heads to bare metal and countersink
  • Prime with a stain blocking rust inhibiting primer
  • Caulk, fill or patch depressed nail heads and sand smooth.