the strength of walls constructed with cored brickand those constructed with solid brick. Resistanceto moisture penetration is about the same for bothtypes of walls. The most easily available brick thatwill meet the requirements should be used whetherthe brick is cored or solid.SAND-LIME bricks are made from a leanmixture of slaked lime and fine silicious sand,molded under mechanical pressure and hardenedunder steam pressure.Types of BondsWhen the word bond is used in reference tomasonry, it may have three different meanings:STRUCTURAL BOND is a method of inter-locking or tying individual masonry units togetherso that the entire assembly acts as a singlestructural unit. Structural bonding of brick andtile walls may be accomplished in three ways: first,by overlapping (interlocking) the masonry units;second, by the use of metal ties embedded inconnecting joints; and third, by the adhesion ofgrout to adjacent wythes of masonry.MORTAR BOND is the adhesion of the jointmortar to the masonry units or to the re-inforcing steel.PATTERN BOND is the pattern formed bythe masonry units and the mortar joints on theface of a wall. The pattern may result from thetype of structural bond used or may be purely adecorative one in no way related to the structuralbond. Five basic pattern bonds are in commonuse today, as shown in figure 7-52. These arerunning bond, common bond, stack bond,Flemish bond, and English bond.RUNNING BOND is the simplest of the basicpattern bonds; the running bond consists of allstretchers. Since there are no headers used in thisbond, metal ties are usually used. Running bondis used largely in cavity wall construction andveneered walls of brick and often in facing tilewalls where the bonding may be accomplished byextra width stretcher tile.COMMON or AMERICAN BOND is avariation of running bond with a course of full-length headers at regular intervals. These headersprovide structural bonding, as well as pattern.Header courses usually appear at every fifth,sixth, or seventh course, depending on thestructural bonding requirements. In laying out anybond pattern, it is important that the corners bestarted correctly. For common bond, a three-quarter brick must start each header course at thecorner. Common bond may be varied by usinga Flemish header course.STACK BOND is purely a pattern bond.There is no overlapping of the units, all verticaljoints being aligned. Usually, this pattern isbonded to the backing with rigid steel ties, butwhen 8-in.-thick stretcher units are available, theymay be used. In large wall areas and in load-bearing construction, it is advisable to reinforcethe wall with steel pencil rods placed in thehorizontal mortar joints. The vertical alignmentrequires dimensionally accurate units, or carefullyprematched units, for each vertical joint align-ment. Variety in pattern may be achieved bynumerous combinations and modifications of thebasic patterns shown.FLEMISH BOND is made up of alternatestretchers and headers, with the headers inalternate courses centered over the stretchersin the intervening courses. Where the headers arenot used for structural bonding, they may beobtained by using half brick, called blind-headers.Two methods are used in starting the corners.Figure 7-52 shows the so-called FLEMISHcorner in which a three-quarter brick is used tostart each course and the ENGLISH corner inwhich 2-in. or quarter-brick closures must be used.ENGLISH BOND is composed of alternatecourses of headers and stretchers. The headers arecentered on the stretchers and joints betweenstretchers. The vertical (head) joints betweenstretchers in all courses line up vertically. Blindheaders are used in courses that are not structuralbonding courses. The English cross bond is avariation of English bond and differs only in thatvertical joints between the stretchers in alternatecourses do NOT line up vertically. These jointscenter on the stretchers themselves in the coursesabove and below.Masonry TermsSpecific terms are usedvarious positions of masonryto describe theunits and mortar7-33
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