A reader's Painting question: movement cracks

Chin L.. from. Melbourne Australia. had this question about movement cracks.

Hi Bill,
Many thanks for the quick response.
Pouring water in to soften the soil is a great idea (especially for a 60 year old guy!). I will try that for sure.
Yesterday I was working on my living room plasterboard ceiling preparing for painting. I noticed a 45 degree line/wrinkly crack stretching from the corner of the top door jamb to the corner where ceiling and wall meet. Bill, I do not know how to deal with this! Any comments? Please?
Other areas had flaking paint which have been scraped away and filled with Quickcote, sanded, then primed with top coat (Dulux) before I paint. This crack has me stumped - not sure how to manage it.
Will appreciate your advice.
Chin

Bill's answer

• For any movement crack that could open up again, painters usually fill any of these types of cracks with flexible acrylic sealer.
• They can buy it in small tubs from paint suppliers and they apply it with either one of those rectangular plastic flexible applicators or putty knife.
• It is the same stuff that comes in tubes, "no more gaps" etc, so I always use that.
• Wipe all the dust away first with a damp cloth so that the filler won't get lumpy too quickly.
• Use it quickly while it is fresh and throw it away when it starts to skin over and gets lumps.