The use of masonry in construction is appealing for a number of reasons. It is fireproof, durable, requires little or no maintenance, and can be configured to satisfy most structural requirements. Masonry units are available in an enormous selection of colors, shapes, textures, and sizes that can be installed for an aesthetically pleasing appearance. Masonry includes brick, block, glazed block, glass block, fieldstone, and cut stone, and labor, tools, and equipment to install these materials.
The use of masonry in construction is appealing for a number of reasons. It is fireproof, durable, requires little or no maintenance, and can be configured to satisfy most structural requirements. Masonry units are available in an enormous selection of colors, shapes, textures, and sizes that can be installed for an aesthetically pleasing appearance. CSI Division 4, Masonry, includes brick, block (CMU), glazed block, glass block, fieldstone, and cut stone, as well as the labor, tools, and equipment required to install these materials.
Brick and block are the two most common types of masonry units, and the process of installing them is referred to as unit masonry. Brick is modular and adaptable, and can be installed in a variety of patterns, called bonds. Concrete masonry units, commonly referred to as CMU, consist of concrete block. CMU is primarily used for walls and partitions that will support a structural load or as the backup for a face brick veneer. It is used extensively in commercial and industrial building applications, and as a foundation material in residential construction. All masonry work is installed with mortar, the “adhesive” that holds the units together. Mortar is spread between the joints of individual masonry units and allowed to harden, which bonds the units together.
In reviewing the contract documents, there are several factors that will affect the cost of masonry work to consider:
- What type of unit masonry will be used? Are there multiple types?
- What is the bonding pattern of the masonry and the size of the mortar joint?
- Is the masonry reinforced vertically and laterally?
- Will scaffolding be required?
- What are the seasonal conditions that will affect productivity when the work is ongoing?
- Will enclosures or temporary heat be required?
- Are there incidentals that need to be considered, such as precast lintels or sills, through-wall flashings, steel lintels, embedded items, chimney components, etc.?
Mortar is a composition of water, fine aggregates (such as sand), cement (Portland, hydraulic, or masonry), and lime. Mortar requirements are specified in the products section of the masonry specifications. The mortar, or its components, is often listed as complying with American Society for Testing and Materials (ASTM), one of the primary agencies that sets standards for masonry products and procedures.
Types of Mortar
The compressive strength of mortar varies with the proportions of the ingredients. The four basic types of mortar and their uses are based on mixing proportions and strengths. They are as follows:
- Type M: A high-strength mortar used primarily in foundation masonry, retaining walls, walkways, sewers, and manholes. In general, Type M mortar is used when maximum compressive strength is required.
- Type S: A relatively high-strength mortar that develops maximum bonding strength between masonry units. It is recommended for use where lateral and flexural strength are required.
- Type N: Medium-strength, general-use mortar for above-grade exposed applications.
- Type O: A low-strength mortar for interior non-load-bearing applications.
Taking off Quantities
Since the mortar quantity required is directly related to the number of bricks or blocks, first calculate the quantity of masonry units in order to determine the quantity of mortar needed. The size of the joints must also be specified or determined in the absence of a specified size. Mortar quantities are typically in CF or can be converted to CY (27 CF = 1 CY). Quantities are frequently determined from established tables.