From DIYinfo.org
In bricklaying, bricks cut to different sizes are all given different names. Cut in half across its width, a brick becomes a half bat. Cut to three quarters of its length, it becomes a three quarter bat and to a quarter of its length, a quarter bat. A brick cut in half along its length is known as a queen closer. This is used for building strengthened corners, or quoins.
The way in which bricks are laid also has its own terminology. A brick laid so that one of its longest sides is visible in the finished wall is known as a stretcher. If it is laid so that one of the ends shows, it becomes a header.
[edit] Bonding
All bricks are laid to a specified arrangement to ensure maximum strength, load bearing property and a uniform appearance. This arrangement is called a bond. As a general rule, no brick should be laid directly on top of another: instead, it should overlap the joints between the bricks above and below it so that there are no straight joints running up the wall. The various bonding patterns in use all follow this rule and ensure that the vertical joints between bricks are staggered.
[edit] Stretcher bond (running bond)
This is the simplest of all bonds. It is used to build walls which are half a brick thick, the minimum thickness of any brick wall (fig. A). Each brick overlaps the one above and the one below it by half a brick's length to provide a simple, strong bond which involves cutting half bricks only at the ends of courses.
Estimating Quantities, Footings & Movement Joints; Requires 60 bricks per 1m2 , not including piers and capping (top layer). The foundation strip should be about 300 mm wide and 460 mm deep. This is made up of a 150 mm layer of concrete on a 300 mm deep bed of hardcore. Deeper footings are advisable on a clay soil. Insert movement joints every 8m for clay bricks, or 4m for blocks or calcium silicate bricks.
[edit] English bond
This bond (fig. B) makes a wall that is one whole brick thick. The strongest of all bonds, it is used wherever high load bearing qualities are called for, such as foundations, retaining walls and man holes. As the bricks overlap by only a quarter of a brick's length, great care must be taken to keep the perpendicular joints aligned and staggered on each alternate course. Otherwise the bond tends to 'creep' as the courses progress and form straight joints where a crack may appear when stress is applied. To keep the bond aligned at its corners, a queen closer is laid end-on next to the corner brick (fig. B).
Estimating Quantities, Footings & Movement Joints; Approximately 120 bricks are needed for each 1m2 of brickwork. It consists of alternate rows (or courses) of headers and stretchers. The foundation strip for a wall up to 1200 mm high should be about 510 mm wide and 510 mm deep. This is made up of a 230 mm layer of concrete on a bed of well compacted soil, clay or rock. For higher walls get professional advice about footings. Insert movement joints every 8m for clay bricks, or 4m for blocks or calcium silicate bricks.
[edit] Flemish bond
This bond (fig. C) also makes a wall that is one whole brick thick. But because it has numerous internal straight joints, it is not as strong as English bond and is used more in decorative work, such as garden walls. When many houses had solid 9 inch brick walls instead of cavity walls, it was the bond most used to build them.
Flemish bond consists of alternate headers and stretchers along a single course. Each stretcher has a header above and below it forming what is called the 'Flemish star' and the decorative properties of the bond are accentuated if this is laid in different coloured bricks. This bond takes a long time to build and also has a tendency to creep if sufficient care is not taken in aligning the vertical joints of alternate courses.' To start each course correctly, it too requires a queen closer next to each corner brick.
Estimating Quantities, Footings & Movement Joints; Same as the English bond.
[edit] English garden wall bond
(fig. D) More complex and not as strong as the standard English bond, this bond incorporates two overlaps, one of half a brick's length, the other of a quarter brick's length. It is an arrangement of three or five courses of stretchers for every course of headers. Care must be taken to ensure that the joints on the header courses align vertically.
Estimating Quantities, Footings & Movement Joints; Same as the English bond. The English garden wall bond is economical because it incorporates a lot of stretchers, so there is less wastage from cutting bricks.
[edit] American bond
This is similar to English garden wall bond, except that it has one course of headers to every five or six courses of stretchers. Because of the deep perpendicular joints between the bricks on the face of the wall and those at the back it is not as strong. Like English garden wall bond, it is used only for decorative outdoor brickwork, not for building construction.
[edit] Flemish garden wall bond
This is a complex arrangement used in decorative brickwork and consists of three or five stretchers followed by a header repeated along the same course (fig. E).
Estimating Quantities, Footings & Movement Joints; Same as the English bond. The headers are arranged so that they are centred in the block of stretchers in the course above.
[edit] Open bond
This bond is purely decorative. Consisting of stretcher courses with a quarter-bat spacing (fig. F), the spacing is decreased at the corners to maintain the bond. The top of the bond can be finished with either a solid course of stretchers or with a course of coping slabs.
Estimating Quantities, Footings & Movement Joints; Requires 50 bricks per 1m2 , for the simplest pattern, not including the piers and capping. The foundation strip and movement joints are the same as the stretcher bond.
[edit] Mortar Composition
Mortar, the material which binds bricks, is composed of a binding material, such as cement or lime and a fine aggregate such as sand and water. Bricklaying sand for general use should be graded either 'soft' or 'fine' for best results.
For all mortars, the specified quantities must be mixed to correct and constant ratios over the whole of the project. Where this rule is not observed, cracking caused by uneven expansion and contraction occurs and the difference in the mortar mix shows through as colour changes in the finished work.
For general and normal house construction six parts of sand to one of cement is the correct ratio, but variations on this mix can be used according to the needs of the bond. Take advice from the brick supplier to ensure that the mortar is neither stronger nor weaker than the bricks it is being used with.
To test the water content of a mortar mix, press a trowel into it. If the impression made remains for a minute or more, the mix is of the correct consistency. If the edges around the impression crumble, the mix is too dry. If the impression fills up with water, the mixture is too wet and more cement and sand in the correct ratio should be added.
Water gives mortar its bonding power. When making up the mix, it is most important to use only fresh, clean water. Dirty water or water from a rain barrel will cause the mix to quickly break up.
[edit] Gauged mortar
Many companies now are producing a form of ready mixed mortar (gauged mortar) which is cement, sand and lime mixed to a ratio of approximately six of sand to one of lime and cement.
The addition of lime makes the mortar less rigid and capable of accommodating more thermal and structural movement, but the addition of too much lime can delay the setting time of the mortar.
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PROPORTIONS FOR MIXING MORTAR |
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Ingredient |
Strong Mix for Garden walls |
Standard Mix |
Approximate Quantities for Strong Mix |
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Ordinary Portland Cement (usually grey; but white or coloured is available) |
1 part |
1 part |
One 40kg bag for every 300-400 bricks |
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Hydrated Lime |
¼ part |
1 part |
Half a 25kg bag for every 400-500 bricks |
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Mortar Plasticiser |
As instructed on container |
About 50 ml for each 40kg bag of cement |
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Clean Building Sand |
3 parts |
6 parts Bricks 5 parts Blocks |
About 0.1 sq m for every 40kg bag of cement |
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Bagged Bricklaying mortar mix |
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One 40kg bag for roughly 150 bricks |
[edit] Plasticizer
To make the mortar easier to use during bricklaying, additives called plasticizers are added. These aerate the mortar and spread the water content evenly throughout the mix, making it more pliable and easier to use for longer periods.
For non structural brickwork, washing up liquid makes a suitable plasticizer. For structural brickwork, a proprietary plasticizer (available cheaply from builders merchants) should be used. The correct quantities to use for different jobs are printed on the back of the container. Gauged mortars contain lime and do not need a plasticizer. Similarly, masonry cement already has a plasticizer added during the manufacturing process.
