Control joints for concrete masonry walls alternative engineered method, tek 103. The expansion joints will reduce brick cracking by changes in temperature, moisture, creep andor settlement, either horizontally or vertically. Expansion joints separate brick masonry into segments to prevent cracking caused by temperature change, moisture expansion, elastic deformation, settlement, or creep. Materials can suffer from initial shrinkage andor subsequent expansion and contraction. To control the expansion and protect the wall structure from cracking under pressure, masons install vertical control joints at specific locations. Control joints in masonry are vertical weak planes intentionally built or cut into masonry to control where cracking occurs. The location of control joints will vary however they can be positioned behind down pipes or above and below window or door openings. Control joints are created to control cracking in concrete block while expansion joints are placed in brick walls to allow expansion. Crack control for concrete brick and other concrete masonry veneers, tek 104. While the great debate wages over the terms expansion joints vs. Brick expansion joints should be placed where different walls encounter each other, reducing thus the possibility of cracks due to differential settlement.
Control joints are a type of engineering device used to limit damage caused by the natural shifts and movements of a building over time. Brick for general use masonry selected to produce characteristic architectural effects resulting from. Eliminating control joints with reinforcement control joints can be eliminated completely if enough horizontal reinforcement is provided. Studies have found that, for walls without the installation of control joints, a minimal brick expansion of 2mm to 4mm caused vertical cracking at building corners ref. We illustrate properlydesigned control joints to prevent cracking in brick walls. For example, the moisture expansion of a 12m 40ft long or high brick veneer panel could be calculated with the bia formula. These cement based products react differently to moisture and thermal changes.
As a rule, vertical joints to accommodate horizontal movement should be provided at intervals of between 7. The control joint is created to control the cracking. Proper application of control joints in brick masonry. 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 get larger as concrete shrinks away from the joints, opening the gap. Site tolerances for masonry control expansion joint placement fire resistance ratings sound transmission ratings weep holes. Rather than allow these objects to crack or break at random, control joints are.
Conventional concrete masonry crack control recommendations, such as those presented in tek 102c, control joints for concrete masonry wallsempirical method ref. The panel can shorten in length allowing potential cracks to occur at the control joint. Masonry movement joint failures international masonry institute. Homes built earlier than that will likely not have these elements, even though commercial masonry has. The engineer should locate the brick expansion joints, not the mason. Control joints when the design calls for the use concrete masonry units cmu, expansion joints, as defined for clay masonry will not work. Provide adequately for movement within brick wall systems. Control joints are typically required in exposed above grade concrete masonry walls, where net aesthetic shrinkage cracking may detract from the appearance of the wall, and to limit moisture or air infiltration. Technical notes on brick construction are recommendations on the use of fired clay brick. Relieving masonrys distress concrete construction magazine. The material will expand and shrink with moisture and thermal changes. Deflection caused by an undersized lintel can cause the masonry to deflect at the center of a window opening and develop a vertical crack. Movement joints in masonry walls abbot building restoration.
If this movement is restrained, cracking may result. These joints create a continuous unobstructed opening through the full depth of. An engineered method is presented in tek 103 control joints for concrete masonry wallsalternative engineered method, which is based on limiting crack width to 0. Consequently, according to the national concrete masonry association, control joints must be less than 20 feet 6. Without the expansion control joints, cracks are most commonly seen because the stress energy must find another way out. In addition to the basic material characteristics, all exposed walls will be stressed and destressed, by the daily and seasonal effects of the sun, wind and rain, irrespective of walling type. Types of cracks in masonry buildings causes and repair.
Joint reinforcement is typically placed in the bed joints of concrete masonry to help control shrinkage cracking. Control joints should be installed in any masonry assembly that expected to experience net shrinkage over time. Thus, it is important to understand the types of movement in claybased masonry veneer walls and how to control the continue reading managing movement in clay masonry. The reader is referred to tek 104, crack control for concrete brick and other concrete masonry veneers ref. Corrugated control joint anchors allow for the expansion and contraction in a masonry wall that can produce cracking.
It is then possible to evaluate where the control joints need to be placed. Expansion cracks in masonry wall causes of expansive cracks. While these attributes are the primary basis for concrete masonrys. Anchors embedded in masonry mortar joints pavers c. How to evaluate cracks at control joints or expansion. These joints will absorb the pressure created by the expansion by giving the masonry wall flexible space to expand. Table 3 indicates the amount of reinforcement that will meet this criteria for various concrete masonry walls. Control joints for concrete masonry walls empirical method, tek 102b. As a rule, vertical joints to accommodate horizontal movement should.
The masonry structures code as3700 limits the amount of movement to be accommodated at a vertical joint to 15mm, and requires that a gap of at least 5mm should remain after the movement has taken place. Control joints vs expansion joints this tsd is designed to explain the difference and the general rules for using control joints and expansion joints. The ratio of length to height of the panels should generally not exceed 3. The joints are formed by leaving a continuous unobstructed opening through the brick wythe that may be filled with a highly compressible material. Foundation walls traditionally do not include control joints due to concerns with waterproofing the joint.
Ns closed cell neoprene sponge is placed horizontally beneath relieving angle, or in the vertical expansion joint to act as a control joint also. Technical notes on brick construction are free bulletins that contain design, detailing, and construction information based on the latest technical developments in brick masonry. The joint must be located in the interior corner or at least 12 from the corner, creating a. Walls are affected by temperature and moisture change. This movement gives rise to the expansion cracks in masonry walls. Control joints in vertically reinforced walls in plain masonry walls, control joints are typically placed at an.
Used wisely, control joints can reduce or eliminate cracking in concrete masonry unit walls. Cracks in masonry walls types, causes and repair of cracks. Properly design, install, and maintain flashings and weeps. In clay masonry walls, vertical or horizontal expansion joints, or both, may be required depending on the dimensions of the wall. Brick and cmu construction this publication 2012 masonry institute of washington. The horizontal joints between units are called bed joints while the vertical joints are called head joints. If joint reinforcement and control joints are placed properly, cracking should be limited to the control joints. Control joints are typically used in concrete masonry to reduce the occurrence of shrinkagerelated cracking.
It limits the amount of movement to be accommodated at a horizontal joint to 10mm. Control joints for concrete masonry walls alternative engineered method ncma tek 103 expansion joint brick masonry. Calcium silicate masonry should be designed as a series of panels separated by movement joints to control contraction. There are two types of movement joints typically used in masonry construction. Where shelf angles are used to hold the masonry, you can specify a shelf angle unit aka lipped brick to hide the shelf angle. Expansion joints are located above major breaks, openings, or intersections in the structure. I agree with michael pruetts informative explanation of general brick cracking problems. Troubleshooting exterior masonry walls construction.
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. The best caulking material for vertical masonry expansion. The location of control joints will vary however they can be positioned behind down pipes or. They also help control cracks from movements other than shrinkage. Occasionally, concrete brick veneer is substituted for clay brick material during the construction process, and the design documents and details do not address the need for bed joint reinforcing.
The panel can shorten in length allowing potential cracks to occur at the. 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. Rather than allow these objects to crack or break at random, control joints are used to guide excess tension to planned locations. These joints are used in masonry, concrete, and drywall structures to minimize aesthetic and structural damage due to cracking. Difference between control and expansion joints concrete. We have produced thinner and lighter masonry elements in order to reduce both costs and weight. Control joints control joint products are used to reduce restraint and permit longitudinal movement. Residential builders have only recently embraced control expansion joints since the early 2000. Concrete inserts bloklok concrete wedge inserts are embedded into concrete slabs. Site tolerances for masonry controlexpansion joint placement fire resistance ratings sound transmission ratings weep holes. Both concrete and clay masonry may use movement joints to accommodate this movement, although the type of joint is different for clay than for concrete masonry.
These joints create a continuous unobstructed opening through the full depth of the brick wall. Control joints are placed in concrete masonry to help limit cracking due to shrinkage. In brick, the path of least resistance is a straight line. 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. That is why mortar is allowed, but not required in concrete masonry control joints. Control joints in concrete masonry walls shrinkage control joints panelize a wall, allowing shrinkage to take place within a small, relatively unrestrained panel. Cracking of concrete masonry units occur if these tensile stresses exceed tensile strength of the materials. Masonry wall systems wbdg whole building design guide. Mar, 2015 studies have found that, for walls without the installation of control joints, a minimal brick expansion of 2mm to 4mm caused vertical cracking at building corners ref. Older masonry buildings were far less prone to cracking since the thickness of the elements provided greater strength and resistance to tensile stresses.
By accounting for movement in the wall design, cracking can be controlled. See tek 103, control joints for concrete masonry wallsalternative engineered method ref. Clay brick masonry should include solid full head and bed joints. The proper use of expansion joints or crackcontrol joints is not well understood. Why bricks and mortar joints crack advantage masonry. They run in a straight, vertical line from the base up.
The overall cause of cracks is having a constrained structure that is unable to move. Homes built earlier than that will likely not have these elements, even though commercial masonry has incorporated them for decades. The determination as to where to place control joints is based on the material and building movements. Control joints for cement masonry units are more susceptible to cracks due to the size of the units. You still need to have an opening for the control joint where you put your sealant, but it will have the same dimension as the other mortar joints. Apr 07, 2020 control joints are a type of engineering device used to limit damage caused by the natural shifts and movements of a building over time. Movement joints must be part of the building design to avoid cracks in masonry walls. Soft joints installed at horizontal shelf angles, and at vertical control and expansion joints, will accommodate movement and create relief for the bricks expansion. Jul 26, 2019 using expansion joints in your brickwork will separate your bricks into small segments, in which, each segment will act individually, and will behave separately from other segments. The expansion control joint is an intended weak spot within the wall.
They are explicitly written for fired clay brick which. 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. Even though concrete masonry veneer is not structural, it almost always must have bed joint reinforcing and control joints to control shrinkage cracking. Drawings, photographs, tables, and charts illustrate appropriate topics. The joints are formed by leaving a continuous unobstructed opening through the brick wythe that may. Usually, we think of control joints in concrete masonry cmu. Specification for facing brick solid masonry units made from clay or shale c 279. This is why advantage masonry installs expansion control joints in brickwork. Clay masonry expands over time, whilst concrete masonry contracts in the same way. Brick for general use masonry where a higher degree of precision and lower permissible variation in size than permitted for type fbs is required. For detailed information on concrete masonry control joints see nation con. Types of cracks in masonry buildings causes and repair methods. 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.
Masonry walls how to avoid unwanted cracking planning. Movement joints such as control joints are one method used to relieve horizontal tensile stresses due to shrinkage of the concrete masonry units, mortar, and when used, grout. How to evaluate cracks at control joints or expansion joints. The support system must be designed for small deflections typically 1600th of the span to avoid cracking of the masonry. Movement joints are used to control and minimize cracking. Clay brick veneer of the masonry walls normally would have a moisture expansion and a thermal expansioncontraction, which should be absorbed by the brick veneer expansion joints. Cracks in walls and building materials are due to several factors. It is a complex technical issue and should be treated with responsibility. If control joints are not provided, a concrete masonry wall may crack as it. The best caulking material for vertical masonry expansion joints.
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