Cultured Stone
EZ Scaffold Corp.
EZG Manufacturing
Federated Insurance
Fraco USA, Inc.
Hydro Mobile, Inc.
Kennison Forest Products, Inc.
Mortar Net Solutions
Non-Stop Scaffolding
Norton Clipper
Southwest Scaffolding
The Belden Brick Company
Xtreme Manufacturing
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ASTM Requirements for Mortar

Mortar performs many functions: it fills gaps between units, bonds the units together, provides weather protection. Simply changing mortar color or joint tooling provides opportunities for varying architectural treatments. Mortar specifications contained in ASTM C 270, Standard Specification for Mortar for Unit Masonry, spell out material requirements and typical formulations.

Mortar Types: by Proportion, by Property

Mortar types are designated by letter as Types M, S, N, O, and K (every other letter in the word MaSoNwOrK). ASTM C 270 contains two alternative specifications of masonry mortars, property or proportion. Mortar can specified by only one of these methods, not both. Under the proportion specification the type of mortar is created using volumetric proportions of cementitious materials and aggregates as set forth in Table 1 of ASTM C 270. No physical requirements are required of the mortar with this method. The property specification requires pretesting of the mortar mix designs in the laboratory to establish compliance with Table 2 of ASTM C 270. The mortar produced using the property specification must meet the required properties of compressive strength, water retention and air content. Factory blended mortar generally is manufactured to meet the property requirements of ASTM C 270.

Mortar Usage

A wide range of mortar types are available for use, depending on durability requirements, unit types, and the initial rate of absorption (suction) of masonry units. Mortars with a high cement content (Type M and S, for example) are very strong but are not as “workable” as mortar with a lower cement content (Type N or O). A good rule of thumb is to not use excessively strong mortars, with a high cement content, as these mortars are less able to retain water and can be prone to shrinkage cracking. Type S and N mortars are commonly used for veneer and structural applications, although Type N mortar is prohibited in the higher seismic design categories.

“The MCAA keeps my company competitive with other building materials.”

John Smith
John J. Smith Masonry Company
MCAA member since 1990

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