What is meant by type S, type N, etc. mortar ?
Masonry cement and cement mortar is rated with letters according to strength:
Masonry cement strength |
Portland cement equivalent |
Uses |
|---|---|---|
| Type M masonry cement (strongest) |
One bag portland cement one fourth bag lime ALSO: One bag portland and one 70 poundbag type S masonry cement |
Stucco; Structural masonry in commercial buildings. |
| Type S masonry cement (strong) |
One bag portland cement one half bag of lime |
Stucco; Structural masonry such as basements in houses, and light commercial buildings. |
| Type N masonry cement (weak) |
One bag portland cement one bag of lime |
Brick veneer. Type N should never be used for stucco. |
| Type O masonry cement (very weak) |
Mostly lime with a small amount of cement. |
Used in historic work with old, soft bricks. |
Type M is preferred for stucco, but type S may be used.
Type N is used for brick veneer. Not only is it cheaper, but can be cleaned off easily. Please don't ever use type N for stucco.
Type O is used when a weak mortar is preferred for historic brick work. Old, soft bricks expand and move more, and a weaker mortar (supposedly) prevents bricks from "blowing up". Blowing up is when old soft bricks crumble during historic brick rebuilds.
Plastic cement is used in California,and is probably stronger than type M. Plastic cement is portland cement with a small amount of a plasticizer instead of lime.
I may be a little wrong on some of these strengths, but this is the best I remember. If anyone can correct me, please do.