Hair line cracks in new render

Hairline cracks are quite common as new render cures and aren’t always a sign that anything has gone wrong. If the render is solid and not hollow or loose, it’s usually just shrinkage during the drying process. Before painting, allow the render to fully cure as recommended by the manufacturer. A stabilising solution is only normally required if the surface is dusty or friable. If the render is sound, use a good-quality masonry paint suitable for fresh render. If the cracks become wider or continue to develop, it would be worth having the render inspected before decorating. Hope this helps.