Radiata Pine can be difficult to sand at times. As a softer timber you could be fooled into thinking it would be easy to work with - but, that's not the case.
One of the issues is that sap in the boards gums up the sandpaper rendering the paper useless in no time. Pushing the now gummed up sandpaper beyond it's capabilities starts to create lines, grooves and scratches in the timber - and the harder we try, the worse it can become. Very frustrating.
Over the years I've tried, and have now perfected a sanding method that not only allows us to get on with the sanding work, but also leaves it looking fantastic. So, if you happen to have a Radiata Pine under your tiles or carpet give me a hoy, as I'm certain I can help turn it into something that will create a good looking backdrop to your paint, and décor choices.