What is brick masonry?
Brick Masonry is the compound building structures constructed out of individual building units bonded together with mortar. Brick masonry is a type of masonry in which bricks are used as the building units which are bonded together using mortar.
It is analogous to a living body made out of individual cells. Brick masonry is generally used in the construction of infill walls, boundary walls, and foundation walls in case of strip footing. In Nepal, it is the most common form of masonry used in the construction of buildings.
Materials required for brick masonry
Types of Bricks used in Brick masonry
Bricks used in brick masonry can be classified on the basis of the manufacturing process:
- Sun-dried or unburnt clay bricks
These are made by molding the clay into desired shape and drying it off in sunlight. These can only be used for construction of temporary structures
- Burnt clay bricks
Burnt clay bricks are the oldest and most commonly used bricks in brick masonry.
On the basis of quality, they are classified into following
- First class bricks
First-class bricks have a standard rectangular shape and size, burnt red color with well-defined straight edges, and even surfaces. They do not absorb water more than 1/5th of their weight when immersed in water for 1 hour and do not show any sign of efflorescence in drying.
They give off a metallic ringing sound when two bricks are stacked together. They should not break when dropped from a height of 1m.
- Second class bricks
Second class bricks have a standard size but have a somewhat distorted shape, not well-defined edges, uneven surface, and irregular color.
When immersed in water for 1 hour, they do not absorb water more than 1/4th of their weight and may show some sign of efflorescence when dried off. They also produced a metallic ring sound when struck.
- Third class bricks
These bricks have irregular shapes and sizes. They are under burnt bricks emitting reddish-yellow color. They have low crushing strength hence not used for quality brickworks.
- Fourth class bricks
They are bricks of the poorest quality. They cannot be used in the construction of brick masonry instead they used as aggregates in the production of concrete.
- Fly-ash bricks
Fly ash bricks are made out of Fly ash and water. They have a high content of Ca0 which helps them to develop self-cementing properties like cement. They are lightweight and have higher frost resistance, high fire resistance, higher strength, lower water permeability than that of burnt clay bricks.
- Concrete bricks
Concrete bricks are manufactured in the site using concrete with cement, sand, smaller coarse aggregate, and water. They reduce the mortar requirements.
- Engineering bricks
Engineering bricks have high compressive strength. They have a higher resistance to frost, chemical attack and have low porosity. They are used in basements for greater strength and damp proofing.
- Sand lime bricks
These bricks are made out of sand and lime. They are used generally in masonry for aesthetic purposes. They have good thermal and sound insulation.
Bricks have also been classified as follows
- Traditional bricks
Traditional bricks are those bricks whose size has not been standardized. The size of such bricks varies from region to region. Their length may vary from 20-25cm, breadth from 10-13cm, and thickness from 5-7.5cm. The nominal size of traditional brick adopted in Nepal is 230*115*55 in mm.
- Modular bricks
Modular bricks have a standard actual size of 19cm * 9cm * 9cm as specified by the Bureau of Indian standard.
Classification of brick masonry on basis of mortar used
- Brick work in Mud mortar
In this type of brick masonry, sticky clay along with or without some fibrous materials are used to fill up joints in between adjacent bricks. These masonries have lower strength. Walls of maximum height of 4 m can be erected using such mortar. These are usually practiced in village to construct temporary houses of lower life span.
- Brick work in Lime mortar
Lime mortar is used to bind the bricks unit together in this type of brick masonry. The lime mortar can be made by using fat limes, hydraulic lime, mixture of lime and cement, or bajra (lime and stone/brick dust). These are used for aesthetic purpose especially in temples in Nepal. Strength of such masonry are superior in compare to mud mortar.
- Brick work in Cement mortar
In this type of brick masonry, cement mortar is used to bind the bricks units together. These result in higher strength of masonry. It is the most commonly used type of brick masonry whether in the construction of walls, fences, foundation, anchor blocks.
General specifications of Brick Masonry
Bricks used in brick masonry shall be of a standard rectangular shape and uniform burnt red in color. Standard brick size is 240 x 115 x 57 mm with a tolerance of -10 mm on length, -5 mm on the width, and ±3 mm on thickness only in case of thick walls.
Horizontal and vertical mortar joints of not more than 10mm are preferred. Depending on the quality and strength requirements of the works, bricks can be hand-formed or machine-made with crushing strength not less than 3.5 N/mm². They should emit a metallic ringing sound when struck together.
They should not absorb more than 25% of water by its weight when immersed in water for 1 hour. They shall not leave efflorescence (whitish substance) on drying. For 1st class brickworks, bricks shall have a well-defined edge, even and hard surfaces, and shall not break when dropped from a height of 1m.
Bricks shall be pre-soaked in before laying. Bricks shall be laid such that vertical joints of adjoining courses do not overlap. In the case of 1 brick thick or thicker walls, brick shall be laid in English bond unless stated.
2) Wall Thickness:
A minimum thickness of one half-brick (115 mm) and a maximum thickness of one brick (240mm) shall be used for non-load bearing wall. While thickness of the load bearing walls
vary from minimum thickness of one brick to thickness as required by the design.
Cement-sand ratio of 1:6 shall be adopted for one-brick and a ratio of 1:4 for half brick thick walls. A small quantity of freshly hydrated lime in a ratio of ¼ to ½ of the cement can be added to the mortar mix to increase its plasticity without tempering its strength.
All plasters should have a cement-sand ratio of not leaner than 1:6. They shall have a minimum 28 days cube crushing strength of 3 N/mm².
Characteristics of brick masonry
- Brick masonry is more durable and stronger than other types of masonry
- Brick masonry increases the asset value of the building
- Building with brick masonry have adequate thermal insulation than other types of masonry
- It does not require dressing of bricks like in that of stone masonry
- Brick masonry can easily be maintained and repaired.
Types of Bonds in brick masonry
Bonds refers to the method of arrangement of bricks in each course such that the vertical joints of the successive course do not overlap with each other.
When a brick is laid with its longer dimension along the length of the wall then it is called a stretcher and when it is laid with its width along the length of the wall then it is called a header Types of bonds in Brick masonry are list out as follows:
- Stretcher bond
- Zig-zag bond
- Header bond
- Racking bond
- English bond
- Garden wall bond
- Flemish bond
- Dutch Bond
- Rat-trap bonds
Most commonly used bonds in brick works are described below
To Read in Details with Picture, Click Here– Bonds in Brick
1) Stretcher bond
In this type of bond, all brick units are laid as stretchers. Stretcher bond results only in a half-brick thick walls. This bond is also known as running bond usually adopted in case of construction of partition wall, parapet walls.
Each alternate course in these types of binding commences with a half brickbat which prevents overlapping of vertical joints in the consecutive course.
2) Header bond
In this type of bond, all the brick units are laid as headers on the faces of the wall. The overlap of the vertical joint in the successive course is obtained by placing a bat of 3/4th of the length of the brick at quoins (at joint of two perpendicular runs i.e. corner).
This type of bond is mainly used in the construction of footings for the better transverse distribution of load. It is applicable in the wall with a certain degree of curvature in plan, arcs, and coping of parapets.
3) English bond
It is a type of bond which consists of alternate courses of header and stretcher. The vertical joints in each type of course (header and stretcher) align over each order in a straight path. To prevent the overlapping of the vertical joints in a successive course, a queen closer is placed after the first header unit in the header course.
A queen closer is half the width of a whole brick. A stretcher should have a minimum overlap of 1/4th of its length over the header unit. Brick masonry with a thickness equal to an even a number of half brick has similar bond faces at the back and front, whereas those with thickness equaling to an odd number of half brick have opposite bond faces in the back and front.
In addition, the header course in structure with such odd thickness starts with a quoin header. In the case of a very thick wall, the mid-portion is filled with only header coarse with thin joints. English bond is considered as the strongest type of bond.
These type of bond is suitable in load-bearing masonry structures but it can be expensive and less pleasing if used for aesthetics purposes
4) Flemish bond
It is a type bond in which alternate header and stretcher occur in a single course. Every alternate course starts with a header at the corner followed by a queen closer and a stretcher respectively in addition to a quoin header in face normal to that of corner header to prevent overlapping of vertical joints in successive courses.
In-wall with a thickness equal to an odd number of half bricks, a half brickbat is placed in the middle of the masonry whereas in walls with a thickness equal to even half brick (except 1 brick thick), a half brickbat and a quarter bat are used to prevent the joint of the successive course to overlap. Flemish bond is further divided into two types:
- Single Flemish bond
Single Flemish is a combination of English bond and Flemish bond in which the front or facing wall consists of Flemish bond and the back wall or non-facing face consists of English bonds in each course.
The single Flemish bond can be adopted only in walls more than or equal to one and a half brick in thickness. This bond improves the aesthetic of the face of the wall and also ensure its strength characteristics.
- Double Flemish bond
In contrast to Single Flemish, Double Flemish Bond consists of headers and stretchers laid alternately at both front and back face.
Brick masonry with Flemish bonds has lesser strength and compactness in comparison to one with an English bond. On the order hand, Flemish bonds require fewer bricks per m3 of brickwork and have a more pleasing appearance than English bonds.
5) Rat trap bond
Click here to Read in detail with Picture– Rat Trap Bond
In the Rat trap bond, bricks are placed in a vertical position in the form of a shiner (stretcher in the vertical form) and rowlock (the header in the vertical form) with a cavity in between the shiner at back and front face. It is also known as the Chinese bond.
The major advantage of a Rat trap is that it reduces the required number of bricks and mortar by 30%. This makes it more economical in building construction. The presence of a cavity improves the thermal insulation of the Rat trap masonry.
The bottom and top course, sill and lintel course along with the sides of the opening should be solid to support windows and doors. Cavities in the Rat rap bind can be provided with rebar and filled with PCC to strengthen the structure against earthquakes. Rat trap bond requires bricks with well-developed edges and smooth surfaces, thus it requires special care during construction.
Materials and Tools Required in Brick works
- Mortar mix
- Pre-soaked Bricks
- Measuring tape
- Water level,
- Plumb bob
- Brick cutter
- Theodolites for layouting if necessary
- Safety equipment like gloves, googles etc
Procedure of Construction of brick masonry
- Preparation works
The layout of the structure should be set on the site using theodolite or measuring tape marked with chalk or gypsum powder or flour especially for brickwork in the foundation.
Pre-soaked bricks should be stacked on the site to cut the haul time.
- Construction procedure
- Prepare a mortar mix of Cement sand ratio not leaner than 1:6 in water. The quantity of mortar prepare which should be finished within 30 minutes of the mix. Otherwise, admixtures are required to be added which prolongs setting time and workability.
- Place a 25mm thick layer of mortar on the construction line which acts as the level surface of laying the bricks.
- Lay the first course of brick on the mortar bed and shove them into the mortar to place them firmly, and fill the vertical joint.
- The recommended mortar joint is of 10mm thickness.
- Threads can be extended from one to another end of the structure to guide the construction and to ensure that the bricks are laid in perfect horizontal
- Fill mortar on the frog of the previous brick course and lay the second course of bricks firmly on the mortar and fill the vertical joints.
- Level devices and water level pipes can be used to check the level of each course whether they are uniform or sloping. Sloping courses are not acceptable.
- Plumb bob shall be used to check the verticality of the wall erected. It can be used at the corners and other wall surfaces to check whether bricks are protruded out or not.
- Course pattern and use of queen closer, quoin header, and other brickbats may vary with the thickness of the wall and type of bonds.
- Other courses can be laid in a similar way.
- The height of brickwork that is permitted to be erected in a single day should not exceed 1.5m
Points to be considered in brick masonry construction
- Bricks used should be of 1st or at least 2nd class in case of construction of permanent structure like walls and foundation.
- Bricks should be presoaked in water before use.
- The verticality of the wall erected should be checked in each course along with the level of each course.
- All the joints should be flushed properly and filled with mortar without leaving any cavities.
- The thickness of mortar joints must not exceed 13mm in any case and they must be uniform as far as possible.
- Frogs of the bricks should always face upward in case of header and stretcher.
- The wall should be truly vertical with each course adequately leveled.
- The thickness of each course should be uniform.
- Brick masonry should be regularly cured for 2 weeks.
- Brick masonry should be left with toothed ends whenever the work is halted.
I hope this article remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Jenish Shakya