cracks in the render outside should i worry

Render is a thin, rigid coating over a substrate that moves. Some cracking is normal and expected. The useful skill is telling the cracking that reflects the render's own shrinkage from the cracking that is telling you the wall behind it has moved.

Usually cosmetic

• Fine, map-like crazing spread over an area, which is shrinkage in the render itself.
• Straight, fine cracks that follow the line of a control joint or a change in substrate.
• Fine cracking around a window corner that has not widened over time.

Worth assessing

• Cracks wide enough to fit a coin, or that have visibly widened over months.
• Diagonal cracks that step through mortar joints, particularly running from window and door corners.
• Cracks where one side sits proud of the other, which indicates differential movement rather than shrinkage.
• Cracking accompanied by doors or windows that have started to bind, or by floors that have gone out of level.
• Cracking that appears seasonally and closes again, which points at reactive clay soil moving with moisture.

Deal with the cause

Where movement is soil related, and in much of Australia it is, the cause is usually water: leaking drainage, a downpipe discharging at the surface, poor site fall, or a large tree drawing moisture unevenly. Fixing the render without fixing the water means doing it again.