Your mason is giving you good advice in waiting for 28 days before painting new mortar. Giving it a chance to cure ensures a good paint bond. And 28 days is exactly what the Brick Industry Association recommends.

How soon can Mortar be painted?

Answer: How soon can MORTAR MIX be painted/coated/sealed? Question: Rapid Set reduces the waiting time before coating. Under dry conditions water-based coating materials such as latex paint can be applied as soon as the product is hardened and dry which usually takes 1 – 4 hours.

How long does Pointing take to dry before painting?

A good rule of thumb is to allow 1 week of good drying conditions for each 5mm thickness of wet material, typically 4-6 weeks will be sufficient.