We just had knockdown ceilings done in the house and would like to know if they have to be primed or painted, now or in the future?
Some say it should be protected and others say it is not necessary. We did prime the bath ceilings with Kilz Premium since the baths are prone to moisture, but are not sure if the main living area needs to be done.
I would paint your ceilings. The drywall mud used for the knockdown texture will absorb moisture if left unpainted. This could cause some expensive problems in the future. Some problems that could occur over time is mold and a lifting of the texture from the surface.
Properly priming and painting will prevent this damage. Plus, it is imposable to clean your ceilings without being painted. Water alone will dissolve drywall mud.