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When working with rendered walls, it is strongly advised that builders use expansion joints where wall sections meet, for a number of reasons. Depending on the architecture of a building, there may be dissimilar materials used on the exterior, varying wall thicknesses or areas that experience different stress levels. In such cases, expansion joints, or movement joints, provide several notable advantages to the homeowner.
A wall may be rendered with brick, stone, cement, mud or similar substrates for a variety of looks. As such, rendered walls will often be composed of different material than adjoining surfaces, and with a different thickness. Expansion joints make it easier to join these dissimilar surfaces while allowing for different rates of expansion as can be expected when using a variety of materials.
Exterior walls are subject to expansion and contraction under varied weather conditions. The rate at which these changes occur will vary according to the substrates used. Where these walls are joined to other surfaces, the joints can be subject to cracking or separation, due to differing rates of expansion and contraction. To mitigate cracking, placement of expansion joints will allow wall sections to expand and contract independent of one another.
Expansion joints are designed to flex and bend so that they permit wall sections to move back and forth without causing stress fractures in the substrate. These joints provide vertical and horizontal articulation when a building’s foundation settles.
Expansion joints also offer a visual reference for building inspectors that can help identify foundation settling before it becomes a more serious issue. The width of an expansion joint can be measured periodically to monitor for potential structural problems, for example. Judicious placement of expansion joints will limit stress build-up in the substrate in order to reduce the risk of cracking along lengths of an exterior wall.
Additionally, expansion joints should be used where there are changes in loading. For example, where an exterior wall supported by a block foundation abuts a wall on a concrete slab. These joints also permit natural movement between a building’s foundation and its footing.
For expert advice on how and where expansion joints should be located when rendering exterior walls, contact a licensed professional building inspector near you. A quality building inspection will identify potential issues in your structure before your work begins. Stress cracking is unsightly and expensive work to correct. Avoid the added cost and labor of repairing them by installing expansion joints.