Why do I have to repaint my house but not my car?

You can do a simple test. With a Stanley knife, score a cross-hatch pattern of lines 3mm apart into the paint. Apply some sturdy tape over the top and if little diamonds of paint pull away with the tape, you will have no choice but to go back to bare wood.

On the house we inspected to illustrate this article, most of the existing paint on the northern side had given up and needed to be removed completely. However, a couple of sections of the lower weatherboards up to waist height had been repainted in the past, so they could be painted over.

If the paint is acrylic, don’t attempt to sand it off. It doesn’t sand well. It just heats up and tears up into little balls.

Occasionally, says Rob, paint fails between layers. It’s rare, but he has seen an early latex paint flaking off an older glossy enamel topcoat. In that case the painter could just remove the latex with a scraper and prep the old enamel by sanding it. 

The easiest way to prep old enamel paint is to use an adhesion primer designed for that type of paint

“Why do I have to repaint my house every 10 years but the paint on my car will last for 30?” Rob is asked that at least once a year. There are a couple of answers.

Car paints typically cost $300 or $400 a litre, maybe 10–20 times the price of house paint. They are also applied in atmosphere-controlled environments, to perfectly prepared surfaces, at computer-controlled depths, and then baked on in many layers, including clear coats. Need we go on?