Masonry

Masonry

1. MASONRY Construction of building units such as bricks, stones or precast concrete blocks bonded with mortar. Types: Stone masonry, Brick masonry, Hollow concrete blocks masonry, Composite masonry Masonry CONSTRUCTION IN BRICKS OR STONES MORTAR (CEMENT +WATER + AGGREGATES) (BONDED)

2. Functions of mortar Provides for full bearing Seals between masonry units Adheres / bonds masonry units Aesthetics Subdivide space Provide thermal and acoustic insulation Provide fire and weather protection

3. Use of masonry in various places Foundation Walls Structural Support Walls Facing Materials Decorative Walls

4. TYPES MASONRY BRICK MASONRY STONE MASONRY Systematic arrangement of bricks and bonding them together with cement mortar. Construction carried out using stones with mortar

5. Definition of terms used in masonry Face Surface of the wall exposed to the weather. Material used in the face of the wall is known as Facing. Back Surface of the wall which is not exposed to the weather. Material used in the back of the wall is known as Backing. Course Horizontal layer of masonry unit Thickness of a course = Thickness of modular brick + Thickness of one mortar joint (in brick masonry)

6. Corbel Projecting stone to serve as support for truss or weather shed etc. Should extend at least two-thirds of their length Generally moulded and given ornamental treatment. Cornice an ornamental moulding near the top of a wall just below the ceiling. Penetrates the full width of the wall; weathered and throated to dispose off rain water Coping Covering of stone, brick of teracotta placed on exposed top of parapet or compound wall to prevent seepage of water It is weathered and throated

7. Weathering Provision of slope on the upper surface as sills, cornices. Throating Groove provided on the underside of projecting elements such as sills, cornices so that rain water can be discharged clear off the wall surface. Toothing Bricks left projecting in alternate course for purpose of bonding future masonry work Lacing course Horizontal course of stone blocks provided to strengthen a wall made of irregular courses of small stones.

8. MATERIALS FOR STONE MASONRY Following two materials are used for stone masonry: Mortar Stones Mortar is a homogenous mixture produced by mixing of binder with inert material (such as sand) and water to make a paste of required consistency and is used to bind a masonry unit. Cementitious ingredients such as cement, lime and materials which cause adhesion when dries such as clay, mud are used as mortar. Lime mortar  is a type of mortar composed of lime and an aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, dating back to the 4th century BC. It is prepared from hydraulic and semi hydraulic limes corresponding to Class A and Class B. Cement mortar composes of cement, sand and mortar. More suitable for making high strength mortars. Lime Cement mortar also known as Gauged or composite mortar. Rate of stiffening of lime mortar is improved.

9. Stones used for masonry should be durable, hard, tough and free from weathering, decay or defects like cavities, cracks etc. They should be obtained by quarrying large massive rock and not by breaking small size boulders having rounded faces. Rocks are divided into 3 groups: Igneous, Sedimentary, Metamorphic Igneous rocks: Suitable for heavy engineering works such as masonry bridges, piers Sedimentary rocks: used for floors, steps and walls (limestone) Metamorphic rocks: used for floors (marble) Purpose Type of stone Heavy engineering work Granite Masonry work in industry area Granite, sandstone General building work Limestone, Sandstone Face work of buildings Marble, granite

10. CLASSIFICATION OF STONE MASONRY Rubble masonry Ashlar masonry Rubble masonry W all is made up of stones of irregular sizes and shapes i.e. stones are roughly dressed. The stones from the quarry are broken into small pieces and ar e directly used in construction work. Ashlar masonry Wall is made of accurately dressed stones with extremely fine bed and end joints. Block may be either square and rectangular shaped.

11. Rubble masonry Following types: 1 . Random rubble masonry Un-coursed random rubble masonry: Roughest and cheapest form of stone walling. Stones are of different sizes. Greater care must be taken to arrange them so that they distribute loads uniformly and no long vertical joints are formed. Coursed random rubble masonry: Work is roughly levelled up to form courses of 30 cm to 40 cm thick. All courses are of not same height. For construction, quoins are built first and line is stretched between tops of quoins. The intervening walling is then brought up to this level by using different size of stones. This masonry is better than un-coursed random rubble masonry.

12. Square rubble masonry Un-coursed square rubble masonry : Uses stones having straight bed and sides. Stones are usually squared and brought to hammer dressed or straight cut finish. Good appearance can be achieved by using risers( large stone) , leveller (thinner stones), and sneck (small stones) in a pattern having their depths 3:2:1. Coursed square rubble masonry: Same stones as uncoursed masonry but the work is levelled up to courses of varying depth. Courses are of different heights. Each course consists of quoins, throughs of same height with smaller stones built in between upto the height of large stones.

13. Polygonal rubble masonry The stones are hammer finished on face to an irregular polygonal shape. These Stones are bedded in position to show face joints running irregularly in all directions. Two types: Rough picked and close picked. Flint rubble masonry Flint or cobbles used; may be coursed or uncoursed ; thickness from 7.5 to 15 cm; length 15 to 30 cm; made of silica; stones are hard but brittle. Strength of flint wall may be increased by lacing courses of bricks or long stones at vertical interval of 1 to 2 metres. Dry rubble masonry Coursed; mortar not used in joints; cheapest and require more skill in construction; used for non load bearing walls such as compound wall.

14. Dry rubble masonry

15. Ashlar Masonry Ashlar fine tooled : Finest type of stone masonry; stones are cut to rectangular sizes; beds, joints and faces are chiselled to remove unevenness; thickness of course not less than 15 cm; thickness of mortar joint should not be more than 5 mm Ashlar rough tooled : exposed face is dressed by rough tooling; a strip of 25 mm wide made by chisel is provided around the perimeter of the rough dressed face of each stone. Thickness of mortar should not be more than 6mm.

16. Ashlar rough tooled

17. 3. Ashlar chamfered : Strip provided around the perimeter of exposed face is bevelled at angle of 45 by chisel to a depth of 25 mm. Due to this a groove is formed in between adjacent blocks of stone. 4. Ashlar facing : Provided along with concrete block or brick to give better appearance; beds and faces of each block are properly dressed. Exposed faces of stone are rough tooled and chamfered.

18. Tools for stone dressing

19. Types of surface finishes Pitched Faced Dressing- The edges of a pitched faced dressed stone shall be level and shall be in the same plane being absolutely square with the bed of the stone. Superfluous stone on the face shall be allowed to remain there and left raised in the form of a natural rounded cobble stone. The minimum width of pitched faced dressing round the four edges of the face of the stone shall be 25 mm. Hammer Dressing - A hammer dressed stone shall have no sharp and irregular corners and shall have a comparatively even surface so as to fit well in masonry. Hammer dressed stone is also known as hammer faced, quarry faced and rustic faced.

20. Plain finish : surface made smooth with a saw or chisel. Vermiculated finish : After having the stone to a level and smooth finish, marginal drafts are sunk about 10 mm below the surface. These sinkings are cut to form ridges; gives worm eating appearance Polished finish : Used in marbles, granite. Glossy surface; Polished manually or with machine

21. Lewis Pin - Single Pin A lifting device for blocks of masonry consisting of two cranked pins attached to a steel ring.  The pins are inserted into a hole cut in the top bed of the stone and a hoist can then be used to lift the block.

22. Chain dogs Hooks known as dogs fit into 20 mm deep holes or depressions made in the stone to be lifted. Dogs are connected to hoisting chain When the chain is lifted, dogs bite into the stone and hence a firm grip is maintained.

23. Chain lewis A  chain-linked lewis  or  chain lewis  is made from two curved steel legs, linked by three steel rings. The legs fit into a seating cut in the top of the stone, above the centre of mass. When the top of the curved legs are pulled together by the rings, the bottom portions are forced into the lower part of the seating, thereby providing enough friction to lift the stone.

24. Three-legged lewis  Also known as a  dovetailed lewis ,  St Peter's keys , or a  Wilson bolt  fits into a dovetailed seating in the top of a building stone. It is made from three pieces of rectangular-section 13 mm-thick steel (legs) held together with a shackle, allowing connection to a lifting hook. The middle leg is square throughout its length. The outer legs are thinner at the top, flaring towards the bottom. Held together, the three legs form a dovetail shape.

25. Joints in Stone masonry Butt joint : commonly used joint; dressed edges are placed side by side Rebated or Lapped joint : provided in arches, gables, copings to prevent movement of stones; length should not be less than 70 mm. Tongue and grooved joint or joggle joint : prevent sliding along joints; made by providing projection in one stone Tabled joint : prevent lateral movement of stones such as in sea walls; made by forming a joggle of 30-40 mm Cramped joint : cramp made of non-corrosive metal such as copper; holes made in adjacent stones; cramp placed to depth of 4-5 cm; after placing cramp, joint grouted with cement, lead or asphalt.

26. BRICKS COMPOSITION Alumina : - A good brick earth should contain 20 to 30 percent of alumina. This constituent imparts plasticity to earth so that it can be moulded . If alumina is present in excess, raw bricks shrink and warp during drying and burning. Silica -A good brick earth should contain about 50 to 60 percent of silica. Presence of silica prevents cracks, shrinking and warping of raw bricks. It thus imparts uniform shape to the bricks Excess of silica destroys the cohesion between particles and bricks become brittle. Lime – A small quantity of lime is desirable in finely powdered state to prevents shrinkage of raw bricks. Excess of lime causes the brick to melt and hence, its shape is lost due to the splitting of bricks.  

27. Oxide of iron - A small quantity of oxide of Iron to the extent of 5 to 6 percent is desirable in good brick to imparts red colour to bricks. Excess of oxide of iron makes the bricks dark blue or blackish. Magnesia - A small quantity of magnesia in brick earth imparts yellow tint to bricks, and decreases shrinkage. But excess of magnesia leads to the decay of bricks. The ingredients like iron pyrites, alkalies , pebbles, organic matter should not present in good brick earth

28. TYPES OF BRICKS Traditional bricks Not standardized in size; dimensions vary; commonly adopted 23 cm x 11.4 cm x 7.6 cm Modular bricks BIS standards Nominal size : 20 x 10 x 10 (cm) Actual size : 19 x 9 x 9 (cm)

29. Header A full stone or brick unit whose length is perpendicular to the face of the wall. In case of stone masonry, header is sometimes called Through stone. Stretcher A full stone or brick unit whose length is parallel to the face of the wall Header course A course of brick showing only headers on the exposed face of the wall Stretcher course A course of brick showing only stretchers on the exposed face of the wall

30. Bond Overlapping of bricks or stones in alternate courses, so that no continuous vertical joints are formed and individual units are tied together. Quoins Exterior angle or corner of wall. The stones or bricks forming the quoins are known as Stone quoins or Quoin bricks. If the quoin’s width is parallel to the face of the wall, it is known as quoin header . If the length is parallel to the face of wall, then it is called quoin stretcher Queen Closer Portion of brick obtained by cutting a brick length-wise into two portions. It is half as wide as the full brick.

31. King Closer Obtained by cutting off the triangular pieces between the centre of one end and the centre of the other (long) side. Bevelled Closer Whole length of the brick is bevelled in such a way that half width is maintained at one end and full width is maintained at the other end.

32. Mitred Closer It is a brick whose one end is cut splayed or mitred for full width. Angle of splay may vary from 45 o to 60 o . One longer face is of full length of the brick while the other long face is small in length Bat Portion of the brick cut across the width. If the length of the bat is equal to half the length of the original brick, it is known as half bat. A three quarter bat is the one having its length equal to three quarters of the length of a full brick. Bevelled bat If a bat has its width bevelled (sloped), it is known as bevelled bat.

33. Perpend Vertical joint on face of wall, which lies directly above the vertical joints in alternate courses. Frog It is an indentation or depression on the top face of a brick made with the object of forming a key for the mortar. This prevents the displacement of the brick above.

34. Bonds in Brickwork Bonds is the method of arranging the bricks in courses and vertical joints of successive courses are not in same line. Rules for bonding Bricks should be of uniform size Amount of lap should be minimum ¼ brick along the length of the wall and ½ brick along thickness of wall. Use of brick bats should be discouraged except in special locations Vertical joints in alternate courses should be along same perpend .

35. TYPES OF BONDS Stretcher bond Header bond English bond Flemish bond Zig Zag bond

36. Stretcher bond Bricks are laid as stretchers on the faces of wall, length of bricks is along the face Use for walls which have thickness of half brick i.e. 9 cm Used as Partition walls, chimney stacks This bond is not possible if thickness is more

37. Header bond Bricks are laid down as headers, width is along the direction of wall. Used only when thickness of wall is equal to one brick This bond is not suitable for transmitting pressure in the direction of wall, hence not used for load bearing walls. Used for curved brick work

38. Most commonly used bond for all wall thickness Strongest bond; Alternate course of headers and stretchers; Vertical joints of header courses come over each other; same with stretcher. In order to break the vertical joints in the successive courses, it is essential to place queen closer after the first quoin header in each heading course. In a stretcher course, the lap must be minimum ¼ of their length. English bond

39. Flemish Bond Each course is comprised of alternate headers and stretchers. Every alternate course starts with a header at the corner (quoin header). Queen closer are placed next to quoin header in alternate course to develop the face lap.

40. Two types: Double flemish bond; Single flemish bond In double; each course presents the same appearance both in front and back face; presents better appearance than English bond; best suited for economy and appearance In walls having thickness equal to odd multiple of half bricks, half bats and three quarter bats are used. In single flemish ; uses English bond backing and double flemish bond facing Can be used for walls having thickness at least equal to 1 ½ brick

41. Garden wall bond: This type of bond is suitably adopted for one brick thick wall which may act as a garden wall or a boundary wall. In garden wall bond, it is possible to build uniform faces for a wall without much labour or expense. This type of bond is not so strong as English bond and its use is restricted to the construction of dwarf walls or other similar types of walls which are not subjected to large stresses. On accounts of its good appearance, this bond is sometimes used for the construction of the outer leaves of cavity walls. There are two types of  garden wall bond , (a) English garden wall bond (b) Flemish garden wall bond

42. English garden wall bond.  The general arrangement of bricks in this type of bonding is similar to that of English bond except that the heading courses are only inserted at every fourth or sixth course. Usually the arrangement consists of one course of headers to three courses of stretchers. A queen closer is placed next to the quoin header of the heading course to give the necessary lap.

43.  Flemish garden wall bond.   This consists of alternate course composed of one header to three or sometimes even five stretchers in series throughout the length of the courses. Each alternate course contains a three quarter bat placed next to the quoin header and a header is laid over the middle of each central stretcher.

44. Raking bond: This is a bond in brick work in which the bonding bricks are laid at any angle other than zero or ninety degrees. This arrangement helps to increase the longitudinal stability of thick walls built in English bond. In this arrangement of bonding, the space between the external stretchers of a wall is filled with bricks inclined to the face of the wall. This bond is introduced at certain intervals along the height of a wall. There are two common forms of raking bond ; ( a) Herring bone bond (b)  Diagonal bond.

45. Herringbone bond a brickwork bond in which the exposed brickwork is bonded to the heart of the wall by concealed courses of bricks laid diagonally to the faces of the wall in a herringbone  pattern. In this arrangement of brick work, bricks are laid in course inclined at 45° in two directions from the centre. This bond is also commonly used for brick pavings .

46. Diagonal bond.   This bond is best suited for walls which are 2 to 4 brick thick. This bond is usually introduced at every fifth or seventh course along the height of the wall. In this bond, the bricks arc placed end to end in such a way that extreme corners of the series remain in contact with the stretchers.

47. Zig-Zag bond: This is similar to herring-bone bond with the only difference that in this case the bricks are laid in a zig-zag fashion. This is commonly adopted in brick paved flooring.

48. Used for making ornamental panels in the brick flooring

49. Comparison of English and Flemish bond English bond is stronger than Flemish bond for walls thicker than 1 ½ brick Flemish bond gives more pleasing appearance and requires greater skill than English bond Broken bricks in the form of bats can be used in Flemish bond

50. Comparison of Brick and Stone masonry Brick masonry can be constructed with less skilled masons in comparison to stone work. Hence brickwork is cheaper. No special lifting arrangement is required for bricks Brick masonry can be used in any type of mortar; mud mortar can be used in low rise houses Better fire resistant than stones

51. Stone masonry is stronger than brick masonry of same wall thickness Life of stone masonry is longer than bricks Stone masonry doesn’t require external plaster. Stone masonry is more water tight than bricks.

52. Defects in Brick masonry Sulphate attack : sulphate salts present in brick react with hydraulic lime in case of lime mortar and with alumina present in cement mortar, volume of mortar increases; chipping and spalling of bricks Crystallization of salts : If bricks containing soluble salts get dissolved with water, appear in the form of fine white crystals on the surface; Efflorescence Drying shrinkage leading to cracks