Know your coats: primers, sealers, and undercoats
What’s the difference? Rob tells us that ‘undercoat’ is an older term for heavysolids paints that blank out different colours on the substrate. It was needed when pigments in topcoats weren’t as good at covering as they are now.
Rob’s rule of thumb is one coat of primer and two topcoats. A second topcoat evens out any thin patches you might have missed when painting the first coat and gives sufficient paint depth for the coating to work.
“It’s hard to get that depth in one coat without drips, or runs, or sagging,” he says. “I’ve never seen someone do one coat and do it perfectly.”
The primer just ensures that the topcoats will stick. And it is designed to work as a thin layer, so a heavy application is definitely not better. Rob even advises priming holes, dents, and gouges before applying a filler.
Note that new weatherboards are often delivered painted, but this is usually just a primer for basic protection during transportation. Make sure that you check the labelling on each plank for painting instructions specific to that product, says Rob. Most will need a proper primer for external use and you should think about applying the first topcoat to the boards before fixing them in place.
Rob doesn’t advise applying gap filler to seal between weatherboards. They need to be free to move past each other, as they expand and contract
Repainting wooden windows is a good test of your mettle
Decks and fences will require thorough cleaning to get them ready for paint or oiling