Fennell Engineering
Call (978) 352-6500
M-F 9-5 or by Appointment
Home Structural Engineering Site Inspections Masonry Walls About Us Testimonials Contact Us


Masonry has been used in building construction for thousands of years. It is primarily used for its durability and various aesthetic effects. In addition to forming the exterior facing, masonry walls can serve as part of the structural frame for a building. Masonry walls also can increase the fire resistance of the wall structure.

Masonry walls can be a single wall or multi-wythe. A wythe refers to the standard width of a wall equal to the thickness and uniformity of the individual sections.

Masonry is typically constructed on site, mixed with mortar, and then cured. Masonry can form structural elements such as bearing walls, columns, support sections and/or the final exterior form. Before and after


Common masonry unit types utilize clay and concrete. These may be solid or hollow, and glazed if desired. Other unit types include cast stone and calcium silicate.


Concrete masonry units (CMU) are made from a mixture of portland cement and aggregates. The units can be made to various dimensions, but typically have face dimensions of eight inches high by sixteen inches wide. Concrete masonry units are typically made in desired forms and then pressure-cured. The units are often used when masonry is to form a load-bearing wall or an interior partition between spaces within a structure.

Concrete masonry units are categorized based on the weight. Structural masonry units are either normal weight or heavyweight. Lightweight units are used for non-load-bearing conditions such as facings.

Larger than brick units, the time required for laying the units is typically less than that for brick. These units can be solid or hollow. The cores provide continuous vertical openings that can be reinforced. Steel bars are placed in the cores with grout surrounding the bars. In this fashion, the wall acts similar to a reinforced concrete structure.


Masonry must be installed on a strong base. Typically a concrete foundation, structural steel or concrete beam system. Most building codes do not allow the masonry to be supported by wood framing, due to the strength loss when exposed to moisture. The support system must be designed for small deviations to avoid cracking of the masonry.


Following the manufacturing process, clay masonry units expand when exposed to moisture. This change results in an accumulated expansion of the wall system that is irreversible. These movements, if not addressed in the design of the masonry, can cause cracking and displacements. Expansion joints are required, particularly in areas exposed to the exterior where units may become wet. Expansion joints are typically required at corners, offsets, changes in wall plane, construction, and at regular spacings.


Masonry walls can be of several different types including Veneer and Structural/Load Bearing Walls. Water penetration through exposed, exterior masonry elements should be anticipated. Water typically flows through separations. This can be due to bond separations, openings, and cracks. Systems must be integrated to address water penetration into the wall system.


Masonry veneer consists of an exterior wythe that forms a surface material only. Lateral support for the masonry veneer is required. Usually by an interior wall, such as a steel frame with water-resistant coating and concrete masonry.

Veneer walls are designed as "drainage walls" due to their resistance to water penetration. An air space or drainage cavity should be installed behind the masonry veneer to allow water to flow down to the base, and directed to the exterior. At the drainage opening, a flashing system should be installed that consists of a three-sided pan, to collect water and direct it to the exterior. End dams are required to prevent water from flowing off and into adjacent construction.

In warmer months, the space behind the brick veneer will typically contain air that is hot and humid. In winter months, this air space can become relatively cold, and condensation may result. Cavity seals are typically recommended at windows, doors, and other openings to prevent the passage of air and moisture to the door or window frames.

Vertical support for the masonry veneer is usually provided at each floor line. For a brick masonry veneer, provisions must be made at each of the vertical supports to accommodate expansion of the masonry.


Structural masonry walls are typically constructed using concrete. The concrete masonry can be reinforced both vertically and horizontally. Vertical reinforcement, installed within the concrete masonry, is typically grouted solid. Horizontal reinforcement utilizes welded wires that are embedded in the bed joints. This reinforcement improves strength and also serves to control shrinkage cracking.

If structural masonry walls are to serve as exterior walls, a second wythe of masonry is recommended. Since water penetration through the exterior wythe of masonry can be expected, the reliance on a single wythe of masonry as the exterior wall is typically not recommended. If required, a barrier should be provided on the exterior surface, such as a fluid-applied, breathable coating or over-cladding. Admixtures can be used in the fabrication of concrete masonry units to reduce penetration. The admixture must be mixed into the mortar to achieve a proper bond. These systems, although effective, should not be relied upon to eliminate water penetration.


Masonry is typically a large thermal mass that can be heated and cooled due to sun and exterior temperatures. Masonry exposed to sunlight can achieve temperatures well in excess of one-hundred degrees. During cold temperatures, masonry will cool, particularly in shaded areas. In design, the thermal characteristics of the masonry are based primarily on the insulation placed in the wall cavity or within the backup wall. The masonry is typically assumed to provide little insulation.


When properly constructed, masonry wall systems require relatively little maintenance. The service life of the masonry can be one hundred years or more, depending on the design. The most common maintenance is the regular replacement of sealant in expansion joints, perimeter of openings, and at wall flashings. The time frame for sealant replacement depends on the sealant used.




Agree to terms & conditions

Read the privacy statement

Call Today (978) 352-6500!