The masonry detailing series mds is an exhaustive collection of illustrative construction details and diagrams produced by international masonry institute imi for architects and engineers to use as a design resource. Pvc control joint is designed for use in solid or cavity masonry wall construction at pilasters, columns, intersections or other joints. Williams materials also seal out moisture and cold air. In plain masonry walls, control joints are typically placed at an opening as it is a weak point subject to cracking due to the reduced masonry cross section. The location of control joints will vary however they can be positioned behind down pipes or above and below window or door openings. Type i concrete masonry units can be used to minimize shrinkage. Vertical cracks in cmu wall structural engineering. Without the expansion control joints, cracks are most commonly seen because the stress energy must find another way out. Control joints placed in concrete masonry walls are. Most cracks in masonry walls are not masonry failures but rather a. One final consideration when placing cmu is the use and location of control joints. Are control joints always needed in poured concrete. This potential shrinkage should be provided for in the design, detailing and construction to minimize shrinkage cracking. Forse consulting, llc august 18, 2017 masonry insights.
When no joint reinforcing is used, national concrete masonry association ncma tek 53, design of concrete masonry for crack control, recommends. Cracks in walls and building materials are due to several factors. Masonry control joint or not structural engineering. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Typically, vertical and bond beam rebar reinforcement serves to resist wind loading. A control joint will tend to open rather than close. Brick and cmu construction this publication 2012 masonry institute of washington.
This allows the adjoining wall to be started without having to adjust or cut brick. Control joints in vertically reinforced walls in plain masonry walls, control joints are typically placed at an. In addition, expansion joints are installed in the clay brick wythe to coincide with. Foundation walls traditionally do not include control joints due to concerns with waterproofing the joint. An information series from the national authority on concrete masonry technology ncma tek 102c 1 control joints for concrete masonry walls empirical method introduction concrete masonry is a popular construction material because its inherent attributes satisfy the diverse needs of both exterior and interior walls.
Control joints are created to control cracking in concrete block while expansion joints are placed in brick walls to allow expansion. Control joints for concrete masonry wallsalternative engineered method, which is based on limiting crack width to 0. However, these joints are designed to include a shear key to transfer lateral loads across the. Masonry detailing series international masonry institute. When materials with different movement properties, such as concrete masonry and clay masonry, are used in the same wythe the movement difference needs to be accounted for in the design. Often you dont want a control joint for structural reasons i. If control joints are not provided, a concrete masonry wall may crack as it. This is the worst and most serious type of cracks in masonry walls and consequently the most difficult to repair. Expansion joints are located above major breaks, openings, or intersections in the structure. The design of sealant joints is discussed in ref 61 and 75. Crack control when designing concrete masonry walls, one aspect that needs to be considered is the location of control joints. When designing concrete masonry walls, one aspect that needs to be considered is the location of control joints.
These joints are used to prevent cracking in the brick as they and the other materials along the perimeter of the building move at different rates and directions. Who among us would think of pouring a 5060 long concrete driveway without jointing it. Masonry wall movement joints abbot building restoration. To control this shrinkage in concrete masonry, hotdipped galvanized joint reinforcing is set in bed joints. Emco block expansion and control joints accessories. In most cases, movement is inevitable and must be accounted for during design if cracking is to be controlled. Control joints must be located so that the structural integrity of the concrete or concrete. Chapter 7 movement part b chapter 7 movement this chapter provides the design requirements for movement joints in masonry to control cracking due to shrinkage of the wall, concrete slab shrinkage, foundation movement and thermal expansion or contraction. Used wisely, control joints can reduce or eliminate cracking in concrete masonry unit walls.
This requires the control joint above the opening to be aligned with the end of the lintel, cross under the lintel via a slip plane, and then proceed through the opening ref. Cracks in masonry walls types, causes and repair of cracks. Control joints should be built into unreinforced concrete masonry at all joints of potential cracking but in no case greater than 6m spacing in articulated residential construction. Control joints are typically required in exposed above grade concrete masonry walls, where shrinkage cracking may detract from the appearance of the wall, and to limit moisture or air infiltration.
Control joints vs expansion joints this tsd is designed to explain the difference and the general rules for using control joints and expansion joints. Cracking of masonry walls gcp applied technologies. Why bricks and mortar joints crack advantage masonry. Concrete masonry units cmu are modular units made from. When control joints are required, concrete masonry only requires vertical control joints. All building materials change in volume due to internal or external mo vement. The best way to control cracking is to install control joints at fairly close intervals throughout the wall. Shrinkage cracks in concrete masonry are not a structural concern. Control joints in masonry are vertical weak planes intentionally built or cut into masonry to control where cracking occurs.
It is recommended that structural engineers locate control joints in structural. The determination as to where to place control joints is based on the material and building movements. It is a continuous vertical joint filled with mortar, but with a bond breaker on one side so that tensile stress cannot develop across the joint. Cracking resulting from shrinkage can occur in concrete masonry walls. Anchors embedded in masonry mortar joints pavers c 410.
Controlling the cracking mason contractors association. Toothing masonry refers to the process of leaving alternating openings teeth for an adjoining block or brick wall to be started from. You are thinking that this could be from lateral forces on the wall in plane. A masonry control joint is a continuous groove formed or cut into a masonry wall forming a plane of weakness to control the location of the eventual cracking.
Without replacement, collapse of the wall could occur. If control joints are to be effective, and perform their intended function, they must be located and installed correctly. Dimex masonry control joints are preformed gaskets that are used in industrial and commercial block construction to reduce air and water penetration. Ive never dealt with in place cracking of cmu from lateral loads would it typically be straight like this or stepped or both. How to evaluate cracks at control joints or expansion. That is why we utilize control joints in cmu walls. Site tolerances for masonry controlexpansion joint placement fire resistance ratings sound transmission ratings weep holes. A control joint is usually a vertical gap through the concrete or concrete masonry wythe and may be filled with inelastic materials. Control joints are placed in concrete masonry to help limit cracking due to shrinkage. Control joints for concrete masonry walls alternative engineered method ncma tek 103 expansion joint brick masonry. The toothing process is also sometimes used when a window or door opening is to be cut into.
Methods for controlling cracks in concrete masonry walls include. Types of cracks in masonry buildings causes and repair. Control joints are vertical separations built into a concrete masonry wall to reduce restraint and permit longitudinal movement. Download control joints for concrete masonry crack control pdf. See tek 103, control joints for concrete masonry wallsalternative engineered method ref. Reinforcement is often required for wind or seismic resistance and it is prudent to utilize it for assisting in table 1criteria for controlling cracking in reinforced concrete masonry wallsa. Concrete masonry veneer units, like all concrete products, tend to decrease in volume as drying occurs. Control joints are typically used in concrete masonry to reduce the occurrence of shrinkagerelated cracking. Spacing control joints concrete construction magazine. Expansion jointscontrol joints by application by category by trademark envirobarrier 10 year system warranty manufacturer, masonry anchors, stone anchors, masonry flashing, reinforcement, air barriers, vapor barriers, hb, hb. Ncma tek 101 crack control in concrete masonry walls ncma tek 102 control joints for concrete masonry walls empirical method proper tooling of the mortar joints during construction is important to minimize hairline cracks between the mortar and the cmu. Traditionally, crack control in concrete masonry has relied on specifying concrete masonry units with a low moisture content, using horizontal reinforcement, and using control joints to accommodate movement. Control joints are continuous vertical mortar joints where a bond breaker is placed between the. In brick, the path of least resistance is a straight line.
Control joints are typically required in exposed above grade concrete masonry walls to control cracking due to the natural expansion and contraction of the block from changes in temperature and. When the movement gets blocked, cracking can often occur and lead to water infiltration, efflorescence, unit failure, interior deterioration, or mold generation. In modern masonry cavity walls, these two different masonry wythes are connected with flexible connections so control joints in the cmu backup wall can be located independently of the expansion joints in the brick veneer. Preventing shrinkage cracks in block walls concrete. A concrete foundation is nothing more than a real thick driveway stood on edge. An engineered method is presented in tek 103 control joints for concrete masonry wallsalternative engineered method, which is. Masonry insights control joints in struc walls masonry advisory. We as an industry almost universally understand that new concrete shrinks. Table 3 indicates the amount of reinforcement that will meet this criteria for various concrete masonry walls. A control joint is a continuous vertical joint filled with mortar, but with a bond breaker on one side so that tensile stress cannot develop across the joint. Control joints masonry association of florida, inc. If the concrete or masonry mortar shrinks before it has sufficient strength to resist these stress cracking results.
Control joints are required in clay masonry to allow for the expansion of clay and they are referred to as expansion joints. If properly installed, the sealant will then accommodate movement. In fact, the primary purpose of wire reinforcement in modern masonry wall systems is simply to help resist cmu shrinkage cracking. Lack of, or inadequate, control joints can produce unsightly and damaging cracking. A control joint is a continuous vertical joint filled. In concrete masonry, control joints are used to create a weakened plane to restrict the volume changes that can result from shrinkage and creep. Control joints in concrete foundation walls masonry.
Similar to expansion joints, control joints must also provide a throughwall separation. We routinely allow 50 to 60 foot spacings between control joints. Forse consulting, llc august 18, 2017 why are masonry control joint locations signi. Repointing and removal of the existing ties is recommended. Plastic concrete in place, after being initially proportioned and mixed to homogenity, occupies greatest volume. Control joints placed in concrete masonry walls are one method of crack control. Shrinkage cracks in concrete masonry are an aesthetic, rather than structural, concern. Cracking of concrete masonry units occur if these tensile stresses exceed tensile strength of the materials. The overall cause of cracks is having a constrained structure that is unable to move. Eliminating control joints with reinforcement control joints can be eliminated completely if enough horizontal reinforcement is provided.
Control joints in concrete masonry walls shrinkage control joints panelize a wall, allowing shrinkage to take place within a small, relatively unrestrained panel. For example, if control joints in concrete masonry. Control joints should be installed in any masonry assembly that expected to experience net shrinkage over time. Extruded from a specially formulated pvc compound with 80 durometer hardness conforming to astm d 2240. Tsd224 technical services digest july 2015 subject. This change must be accommodated in order to prevent cracking, spalling, and displacement of masonry. This is why advantage masonry installs expansion control joints in brickwork.