Brick Masonry

UNIT - III

Chapter - 6 (A)

MASONRY

 

BRICK MASONRY

Brick Masonry is defined as the systematic arrangement of bricks and bonding them together with Cement Mortar or Lime Mortar. The strength of brick masonry depends upon (i) Quality of the bricks, (ii) Quality of mortar and (iii) Method of bonding used.

 

1. TERMINOLOGY

1. Header: See Fig. 1. A brick laid with its Width W parallel to the face or direction of a wall is known as Header.

[Or, a brick laid with its Length L perpendicular to the face of the wall is known as Header.]

2. Stretcher: It is a brick laid with its length parallel to face of the wall.

3. Course: Course is a horizontal layer of masonry.

4. Header Course: It is a course or layer of brickwork showing only headers on the exposed face of the wall.

5. Stretcher Course: It is a course or layer of brickwork showing the stretchers on the exposed face of the wall.

6. Bed: Bed is the lower surface of a brick in each course.

7. Bed Joint: Bed Joint is the horizontal layer of mortar on which bricks are laid.

8. Lap: Lap is the horizontal distance between the vertical joints of successive courses.

9. Quoin: It is a corner of the exterior of the brickwork. 10. Perpends: The vertical joints either in the length or in the cross directions are known as Perpends.

11. Arrises: Arrises are the edges formed by the intersection of plane surfaces of a brick.

12. Frog: See Fig. 2. Frog is a depression on the top face of a brick. It is made for forming a key for the mortar.

13. Brick Bat: Brick bat is a piece of brick designated according to its length. If it is half the length of the brick, it is called a Half Bat as shown in Fig. 3.

A Three-quarter ( 3/4  ) Bat is one whose length is 94 of a brick as shown in Fig. 4.

14. Closer: It is a piece of brick used

to close up the bond at the end of brick course. It prevents vertical joints of successive courses coming one over other. Types of closer are:

(i) King Closer: See Fig. 5. It is obtained by cutting triangular portion of the brick such that half a header and half a stretcher are obtained on the adjoining cut faces.

It is used near door and window openings to get satisfactory arrangement of mortar joints.

(ii) Queen Closer: See Fig. 6. It is a piece of brick obtained by cutting a brick longitudinally into 2 equal parts.  It is placed next to the Quoin Header in header course.

(iii) Bevelled Closer: See Fig. 7. Bevelled Closer is obtained by cutting a triangular portion of the brick, joining half the header and full stretcher. It is used for splayed brick work like jambs of doors and windows.

15. Squint Quoin: See Fig. 8. It is a brick cut such that an angle other than 90° is formed in plan.

 

2. BONDS IN BRICKWORK

Bonding in brickwork is the art of laying mortar and bricks so that strong joints are obtained in the brick masonry. Proper bonding ties the bricks together in the directions of length and height.

The proportion of cement and sand in the mortar varies from 1:3 to 1:6 by volume. A bed of mortar is spread to 10 mm thickness. Bricks soaked in water are placed on the mortar and pressed so that the mortar fills the pores in the bricks faces. Functions of Mortar: (i) Mortar in horizontal and vertical joints ties the bricks together. (ii) It creates even distribution of the compressive stress due to applied loads. Brickwork is not subjected to tensile stresses. (iii) It also makes the wall moisture-proof and air-proof.

 

3. TYPES OF BONDS IN BRICK MASONRY

1. Header Bond, 2. Stretcher Bond, 3. English Bond, 4. Flemish Bond and 5. Raking Bond

1. HEADER BOND [Figs. 9(i) and (ii)]

In Header Bond, all the courses have facing of  headers. Headers alone are visible in elevation. Bricks are laid with their Lengths L per-pendicular to the face of the wall.

Overlap of the joint is equal to W/2. This lap is provided by having three-fourth Brick Bat [ = (3/4) L ] at Quoins of alternate courses.

Uses: Header bond is used for walls of 1 brick thick, footings and curved wall. Stretcher bond cannot be used for curved wall, because it may project beyond the face of the wall.

2. STRETCHER BOND [Figs 10(i) and (ii)]

Stretcher Bond consists only of stretchers in all the courses of the face of the wall.

In this bond, bricks are laid with their Lengths L parallel to the face of the wall. This bond is also known as Running Bond.

Overlap of the joint is equal to L/2. This lap is provided by having Half-brick Bat (= (1/2)L] at Quoins of alternate courses.

Uses: It is used for walls of half-brick thickness only such as partition walls. This bond cannot be used for walls of thickness of one brick or more, because its internal bond is not proper.

3. ENGLISH BOND

It consists of alternate courses of headers and stretchers. Vertical joints of the header courses come over each other. Similarly, the vertical joints of the stretcher courses also come over each other.

English Bond for One Brick Thick Wall

See Figs. 11(i), (ii), (iii), and (iv).

Number of half bricks for one brick thick wall is equal to 2 (Even Number). If the wall thickness is an even number of half-bricks, the same course will show either headers or stretchers on both face and back. That is, the appearance on both face and back are the same.

Features of English Bond

• Alternate Courses: It consists of headers and stretchers in alternate courses in elevation.

• Queen Closer: See Figs. 11(i) and (ii). A header course should never start with Queen Closer, as it will get displaced. A Queen Closer is placed next to the Quoin Header, in each header course to the full thickness of the wall. This is done to break the continuity of the vertical joints in the successive courses. Thus, Lap Joint is provided to create the bond. Queen Closers are not required in stretcher courses.

• Alternate Header: Each alternate header lies centrally over a stretcher.

• Wall Thickness in Even Number of Half-bricks: See Fig. 11. If the wall thickness is an even number of half-bricks, the same course will show either headers or stretchers on both face and back. That is, the appearance on both face and back are the same.

• Continuous Vertical Joints: These should not be allowed except at the stopped end.

• Wall Thickness of Two Bricks or More: Interior or Hearting of these thicker walls should be filled with headers only.

•  Thinner Header Course: There are more vertical joints in the header course than in stretcher course. Hence, the joints in the header course should be thinner than in the stretcher course.

English Bond for One and a Half Brick Thick Wall: See Figs. 12(i), (ii) and (iii).

In English Bond, if the wall thickness is an odd number of half-bricks, the same course will show headers on the face and stretchers on the back or stretchers on the face and headers on the back of the wall.

Elevation is as shown in Fig. 11(ii).

Uses: English bond is the most commonly used bond for all wall thicknesses. strongest type of bond.

4. FLEMISH BOND

Features of Flemish Bond

• In Flemish Bond, headers and stretchers are laid alternately in each course.

• Every alternate course starts with a header at the corner i.e., Quoin Header.

• Queen Closer is laid next to the Quoin Header in alternate course to develop the face lap for creating the bond.

• Every header is centrally supported over the stretcher below it.

•  If the wall thickness is an odd number of half bricks, more brick Bats are to be used.

•  This type of bond gives a better appearance, because the headers are distributed evenly

Types of Flemish Bond

1. Double Flemish Bond

In this, each course presents the same appearance both in front and back faces. Hence, it gives better appearance than English Bond. But, it is not as strong as the English Bond.

Salient Features of Double Flemish Bond

• Every course consists of headers and stretchers placed alternately.

• Queen Closers are placed next to quoin header in every alternate course.

• The face and back of the wall in each course have same appearance.

Double Flemish Bond for One Brick Thick Wall: [Figs. 13(i), (ii), (iii) and (iv)]

If the thickness of the wall is an even number of half-bricks, no bats are required.

Double Flemish Bond for One and a Half Brick Thick Wall [Figs. 14(i), (ii) and (iii)] In this, the Lap is equal to [74 L]. Lap is provided by introducing a Queen Closer next to Quoin Header in alternate courses. The intermediate course starts with a stretcher followed by a header, stretcher, header and so on. Since the thickness of the wall is an odd number of half-bricks, half-bats and three-quarter bats are used.

Uses: This type of bond is not as strong as English Bond. But, it gives a better and uniform appearance than the walls in English Bond. The number of facing bricks used in Double Flemish Bond is less than in English Bond.

2. Single Flemish Bond

See Figs. 15(i), (ii) and (iii).

In this, Flemish Bond is adopted on the face side of the wall and English Bond is adopted on the back side of the wall.

Salient Features of Single Flemish Bond

• It has the better strength of English Bond and the better appearance of Flemish Bond.

• It requires a minimum wall thickness of one and a half brick.

• As in the English Bond, the brick joints are straight in Single Flemish Bond.

• Since the thickness of wall is an odd number of half-bricks, half brick bats are used.

Comparison of English Bond and Flemish Bond

5. RAKING BONDS

Raking course in Raking Bond is provided between two stretcher courses. The bricks are laid at an inclination to the direction of the wall. Raking Bonds are used for thick walls. These are of the following two types:

1. Zig-zag Bond: [Fig. 16] In this bond, the bricks are laid zig-zag for paving or making ornamental finish in the brick floor.

2. Diagonal Bond: [Fig. 17] In this bond, bricks are laid diagonally. Internal placing of bricks is made in one direction only at certain angle of inclination, after face bricks are laid. Bricks cut to triangular shapes are packed in the small triangular spaces at the ends.

 

4. PRINCIPLES OF BRICK MASONRY CONSTRUCTION

[Precautions to be observed in Brick Masonry]

1. IS : 1077 Quality

Bricks should be well burnt, strong, durable, with sharp edges and standard dimensions of uniform colour. They should satisfy IS : 1077 requirements.

2. Soaking in Water

Bricks should be soaked in water just before laying. This is to prevent absorption of: moisture from the mortar and for better adherence of bricks to mortar. [For lime and mud mortars, bricks should not be soaked in water.]

3. Laying Horizontally with Frogs Facing up

Bricks should be laid horizontally with frogs facing up, to facilitate good bonding of bricks.

4. Lapping

Any one brick should lap over at least two other bricks in the course below it.

5. Height of Construction

The height of brick masonry constructed per day should not exceed 10 layers or 1 m to avoid non-uniform settlement of masonry.

6. Vertical Joints

Vertical joints in alternate courses should be in one vertical line.

7. Length of Construction

Length of construction should not be more than 1 m at a time. After this, the brick masonry should be constructed vertically.

8. Checking

All vertical faces should be frequently checked with a Plumb Bob. should be checked for perpendicularity. Also, wall junctions

9. Brick Bats

In the brick work, brick bats should not be used except as Closers.

10. Curing

The constructed brick masonry walls should be cured for one to two weeks.

11. Raked Back

Refer Fig. 9(i). The incomplete end of the brickwork is raked back, by stepping the brickwork.

12. Occurrence of Cracks

Horizontal and vertical expansion joints should be provided in the walls to reduce the occurrence of cracks in the walls.