There’s no flexibility in a brick wall, so even the slightest building movement will result in a crack.
Gather your supplies:
• Flexible gap filler (try Sikaflex–11FC)
• Caulking gun
You’ll also need:
Utility knife; vacuum cleaner; paint scraper; lint-free rag or sponge; solvent for filler; painting equipment; undercoat; acrylic paint to match wall colour.
Use utility knife to remove any loose paint and scrape back edges of crack. Vacuum to remove dust.
Squirt flexible gap filler into crack. Overfill so gap filler is proud of wall.
Use paint scraper to run along wall over gap filler, removing excess and making filler flush with wall. To remove any excess on wall, use rag with appropriate solvent for filler. Let dry.
Spot prime filled areas with undercoat. Let dry. Apply 2 coats of acrylic paint to match wall.