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Guide for the Selection of Masonry Mortars
Exterior, above grade
Load-bearing wall
Recommended mortar
Type N
Alternative mortar
Type S or M
Exterior, above grade
Non-load bearing wall
Recommended mortar
Type O
♦
Alternative mortar
Type N or S
Parapet wall
Recommended mortar
Type N
Alternative
Type S
Exterior at or below grade
Foundation, retaining wall,
manholes, sewers, pavements,
walks, and patios
Recommended mortar
Type S
♥
Alternative mortars
Type M or N
♥
Interior
Load-bearing wall
Recommended mortar
Type N
Alternative mortars
Type S or M
Non-bearing partitions
Recommended mortar
Type O
Alternative mortar
Type N
♦
Type O mortar is recommended for use where
the masonry is unlikely to be frozen when
saturated or unlikely to be subject to high winds
or other significant lateral loads. Type N or S
mortar should be used in other cases.
♥
Masonry exposed to weather in a nominally
horizontal surface is very vulnerable to
weathering. Mortar for such masonry should be
selected with due caution.