Mortar joint finishes impact water resistance and weatherability:
Concave joint is the most weather-resistant. The joint is compressed and curved inward, forming a
dense, compact surface that sheds water effectively.
Weathered joint slopes outward but is less compact than concave.
Raked joint is recessed and can hold water, less weather-resistant.
Extruded joint protrudes and tends to trap water and dirt.
Therefore, concave joints provide the best weather protection.
Reference:
NCARB ARE 5.0 Review Manual, Materials and Assemblies chapter
Masonry construction standards and detailing guides
