Chapter 2: Masonry

Back to chapter

2.9:

Movement Joints in Buildings

JoVE Core
Civil Engineering

É necessária uma assinatura da JoVE para visualizar este conteúdo. Faça login ou comece sua avaliação gratuita.

JoVE Core Civil Engineering

Movement Joints in Buildings

Vídeo Anterior
2.8: Expansion and Contraction in Masonry Walls

Próximo Vídeo
2.10: Types of Building Separation Joints

Idiomas

COMPARTILHAR

English العربية 中文 Nederlands français Deutsch עברית italiano 日本語 한국어 português русский español Türkçe

Slight movements in buildings can occur during the expansion of building units exposed to moisture or the upward heaving of foundations when water in the soil expands while freezing. Movements may form cracks in the building; movement joints such as working joints, structure enclosure joints, surface divider joints, and building separation joints are provided to avoid this. Working joints are used in shingled roofs, where small strips are assembled in an overlapping pattern, tolerating slight movements without any distress. In a cavity wall, the soft joint provided under the shelf angle supporting the non-structural exterior wythe is an example of a structure enclosure joint. Surface divider joints include isolation joints, expansion joints, and control joints. When new additions are made to an existing building, isolation joints are provided, enabling the movement of the new materials without impacting the existing building. Expansion joints are open slots designed to allow the expansion of building materials, while control joints are lines of weakness created where cracks may occur when building materials shrink. Lastly, building separation joints subdivide complex building structures into discrete segments that can be independent of each other's movements.

2.9:

Movement Joints in Buildings

Movement joints in buildings are essential design elements that accommodate inevitable motions caused by various factors such as temperature changes, moisture content variations, and structural deflections. These motions, if not considered in design and construction, can lead to unsightly or dangerous damage. Movement joints are incorporated in different forms to manage these stresses and allow materials to move without causing distress.

The simplest type of movement joints, working joints, are integrated during the construction process. Examples include shingled roofs and wood bevel siding, which allow for thermal and moisture movements. Structure/enclosure joints separate structural from nonstructural elements to prevent load transfer that could cause damage, such as deflection tracks in metal-framed walls or soft joints under shelf angles supporting masonry veneers.

Isolation joints are used to prevent interference between materials that need to move independently, typical in renovations or where concrete slabs meet structural elements. Control joints create predetermined lines of weakness to direct cracking in a controlled manner, commonly seen in concrete sidewalks and plaster walls. Expansion joints accommodate material expansion and contraction, evident in brick walls and curtain wall systems.

Lastly, building separation joints divide complex structures into segments that move independently, categorized into volume-change joints, settlement joints, and seismic separation joints, each addressing specific structural movement challenges.