Stucco News

Question and answers on Stucco and Plastering-- January, 2012




What is meant by type "S" , type "N" etc. mortar ?




                 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 to one bag lime
Stucco; Structural masonry
such as basements in houses,
and light commercial buildings.
Type "N" masonry cement
(weak)
One bag portland cement
one half to one bag lime
Brick veneer.
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.
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.