Types of Bonds
The primary object of a bond is to give strength to masonry.In brickwork, the cross joints in any course shall not be nearer than a quarter of a brick length from those in the course below it. The types of bonds generally in use, their characteristics, situations of use are described below.
The bricks in the facing are laid in alternate courses of headers and stretchers. The header course is commenced with a quoin header followed by a queen closure and continued with successive headers.The stretcher course is formed by stretchers having a minimum lap of one quarter their length over the header. The bond contributes substantially to the strength of brickwork and may be particularly suitable for carrying heavy loads.
Double Flemish Bond
The courses both in the facing and backing are formed with alternating stretcher and headers. In order to obtain the lap, which is equal to one-quarter of the length of bricks, a queen closer is introduced next to the quoin header in alternate courses, the intervening ones commencing with a stretcher, and every header will obtain a location that is central with respect to the stretcher above or below.
The appearance on the face may be considered as more uniform than in English bond. It requires less number of facing bricks than English bond and hence may be more economical where brickwork is faced with special facing bricks and exposed to view.Though considered inferior to English bond in strength this bond may be-suitable for single-brick thick walls in normal house construction, provided a strong mortar such as cement mortar is used.
Single Flemish Bond
This facilitates the facing of wall to be in Flemish bond and the backing in English bond.This will entail the use of snap headers.This attempts to combine practically the better appearance of Flemish bond with the better strength of English bond. However increase in strength over Double Flemish bond is doubtful.
Garden Wall Bond
English garden wall bond consists of a header course with the necessary queen closure next to quoin header to three or sometimes even five stretcher courses running in series with overlap of half-brick between stretcher over stretcher.
Flemish garden wall bond consists of alternate courses composed of one header to three or five stretchers in series throughout the length of these courses.One brick thick walls are easier to construct with these bonds than with pure Flemish or English bonds and save facing bricks considerably in the case of exposed work.
American Bond (also Known as Common Bond)
It consists of one header course to a numberof stretcher courses.This is for general use.It is commonly adopted in America.
In this bond all the courses are stretcher courses and the overlap is usually half brick and is obtained by commencing each alternate course with a half-bat.With a slight variation at the quoin the overlap may be varied to 3/4 or 1/4 brick and the bond is then known as ‘Raking Stretcher Bond’.This is generally used in l/2 brick thick leaves of cavity walls.
The facing of this bond has all the courses as headers only and the overlap, which is half the width of the brick, is obtained by introducing a three quarter bat in each alternate course at quoins.This bond is used for walls curved in plan for better alignment; and preferably in foundation footings of brick masonry for better transverse distribution.
The bonds covered from 2.2 to 2.8 are based on the traditional 225 mm x 112.5 mm x 75 mm brick. These are also suitable for modular bricks. Other bonds, such as, Monk Bond, Dutch Bond, English Cross Bond are in vogue for special conditions.They give different artistic appearance. They give different artistic appearance.