Name: masonry wall joints for temperature and moisture
Uploaded: 2024-09-12T16:16:29.000Z
Duration: 1 min 19 s
Channel: JoVE

Consider a brick wall exposed to continuous rain; the brick absorbs moisture and tends to expand slightly. In the absence of space to expand, compressive stresses develop in the wall, leading to the formation of cracks in the wall.
A continuous opening in the wall, called an expansion joint, has to be provided to allow the expansion in the masonry.&#160;
In the case of a newly constructed concrete masonry wall, as the mortar dries, the wall undergoes shrinkage, which induces tensile stresses.
If these stresses exceed the tensile strength of the wall, shrinkage cracks appear.
These random cracks can be confined along a control joint, an intentionally created weak joint that runs continuously along the wall.
Expansion and control joints are provided where the walls intersect a column or opening and locations where the wall changes its direction, height, and thickness.
Vertical joints are built into the walls when bricks are laid. These joints are often filled with a backer rod and sealed with elastic joint sealers to prevent moisture and air from entering the room.

expansion and contraction in masonry walls

Masonry walls are subject to slight expansion and contraction due to variations in temperature and moisture. Thermal movement in masonry is relatively straightforward to measure and plan for. On the other hand, moisture movement poses more of a challenge. New clay masonry units typically absorb water and expand over time under normal environmental conditions. Conversely, new concrete masonry units tend to shrink as they lose the excess moisture acquired during their production process.
To accommodate these movements without causing damage to the structure, buildings must incorporate specific types of joints. Expansion joints are crucial as they are designed to open or close, allowing the material room to expand or contract in response to changes in moisture and temperature. These joints are often sealed with flexible materials to prevent the infiltration of air and water. Control joints, another essential feature, are intentionally incorporated as planes of weakness within the masonry. These joints are designed to open and manage shrinkage, particularly during the initial curing phase of the masonry.
Both expansion and control joints should be strategically placed in the structure. Common locations include points of geometric discontinuity like corners, changes in the wall&#39;s height or width, and near openings.

Expansion and Contraction in Masonry Walls

Consider a brick wall exposed to continuous rain; the brick absorbs moisture and tends to expand slightly. In the absence of space to expand, compressive ...

expansion-and-contraction-in-masonry-walls

Education

JoVE Core

Civil Engineering

Unit 1

Masonry

KEY TERMS AND CONCEPTS

masonry wall joints for temperature and moisture

Masonry walls change size slightly as temperature and moisture change. Builders account for this movement so the wall does not crack or shift out of place. Thermal movement is usually easy to measure and plan for. Moisture movement is harder to predict.

New clay masonry units often absorb water and expand over time in normal outdoor conditions. New concrete masonry units behave differently. They usually shrink as they lose extra moisture gained during production. These opposite changes make joint design an important part of masonry construction.

Expansion joints give masonry room to open or close as the material expands or contracts. These joints are often sealed with flexible materials so air and water cannot get in. Control joints are another key feature. A control joint is a planned line of weakness in the masonry. It helps manage shrinkage, especially during the early curing stage.

Both expansion joints and control joints must be placed carefully. Common locations include corners, changes in wall height or width, and areas near openings. These points are called geometric discontinuities because the wall shape changes there. Proper joint placement helps protect the structure as the masonry moves.

Masonry Wall Joints for Temperature and Moisture

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Masonry walls change size slightly as temperature and moisture change. Builders account for this movement so the wall does not crack or shift out of place. Thermal movement is usually easy to measure and plan for. Moisture movement is harder to predict. New clay masonry units often absorb water and expand over time in normal outdoor conditions. New concrete masonry units behave differently. They usually shrink as they lose extra moisture gained during production. These opposite changes make...

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key terms and concepts

Learn how expansion joints and control joints help masonry walls handle temperature and moisture changes, including clay and concrete unit movement.

Masonry Wall Joints for Temperature and Moisture | JoVE K12

JoVE Core Civil Engineering offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

Masonry Wall Joints for Temperature and Moisture

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