About This Book
Preservation Brief 2: Repointing Mortar Joints in Historic Masonry Buildings
Published by the National Park Service (Technical Preservation Services), this authoritative guide helps property owners, architects, and contractors properly repair and maintain historic masonry.
Core Concept: Sacrificial Mortar
Mortar joints serve as a wall's first line of defense. They are intentionally sacrificial—designed to deteriorate gradually rather than damage the harder masonry units (brick, stone, or terra-cotta). Repointing (also called pointing or tuckpointing) is the process of removing deteriorated mortar and replacing it with new mortar, with a quality job lasting 30 to 100 years.
Compatible Mortar Requirements
Replacement mortar must prioritize compatibility over modern strength standards:
- Softer and more permeable than the masonry units. Hard modern Portland cement traps moisture and thermal movement, causing brick or stone faces to crack and spall.
- Matched to the original in color, texture, and tooling profile.
- Sand-matched in color and grain size, as these properties govern the joint's final appearance.
Joint Preparation and Application
- Remove old mortar to a uniform depth of 2–2.5 times the joint width. Use power tools with extreme caution—or not at all—on thin or historic joints to avoid widening joints or damaging masonry.
- Pack mortar cleanly, finish with a historically accurate tooling profile (e.g., concave or weathered), and keep joints adequately moist during curing to prevent cracking.
Practice Tests Using This Book
This book is required or recommended for 1 licensing exam. We've written 23 practice questions directly from this material, each one citing the chapter and section it comes from.