What method improves bond strength when placing horizontal mortar joints in a masonry wall?

• A. Use thickened mortar with no tooling.
• B. Use joint finishing with no raking.
• C. Skip joints to speed up.
• D. Proper joint raking and tool finishing to create uniform, well-sealed joints and good mortar compaction.

Answer: (D)

Bond strength in horizontal masonry joints comes from a good mechanical key and a dense, well-sealed mortar fill between courses. Raking the joint removes loose or deteriorated material and creates a rough, keyed surface for the new mortar to grip. This keying helps the mortar lock into place and reduces the chances of cold joints, giving a solid foundation for the next course. After placing the mortar, tooling it properly squeezes excess material, consolidates the mix, and shapes the joint so it’s uniform in depth and texture. The result is a joint that is tightly packed, free of voids, and resistant to water infiltration and movement.

Using thickened mortar with no tooling tends to trap air and leave inconsistencies; finishing without raking removes the opportunity to create a key, weakening adhesion; skipping joints eliminates the bonding surface between courses.