Mixed advantage in masonry sealer

Q Should a sealer be regularly applied to a flagstone walk laid in mortar as well as on an exterior brick chimney? If so, how oftern? Could the same product be used for flagstone, brick, and exposed aggregate concrete? What sealer product should be used? The flagstone walk has developed some cracked mortar joints from slight settling. Should I do anything about this? Bruce H. Morgan Annapolis, Md.

A A masonry sealer cuts down moisture penetration on both a flagstone walk as well as a concrete slab, but that is about as long as it is short. A sealing process requires an annual redoing, and you may regret it against the slight advantage obtained.

Some masonry experts disapprove of putting anything on exterior brick, declaring that sealers are counterproductive. They prefer regrouting the mortar joints, as necessary.

As for the cracking mortar joints between the sinking flagstone, simply clip out the broken mortar and regrout.