Brick Masonry is used to indicate the art of building a structure with bricks . In this Article i will tell you procedure and specification of Brick Masonary
Bricks shall be hand moulded or machine moulded. They shall be free from nodules of free lime, visible cracks, flaws warpage and organic matter. They shall have a frog 100 mm in length 40 mm in width and 10 mm to 20 mm deep on one of its flat sides.
Bricks made by extrusion process and brick tiles may not be provided with frogs. Each brick shall be marked (in the frog where provided) with the manufacturer’s identification mark or initials.
The common burnt clay bricks shall be classified on the basis of average compressive strength as below :
|Class Designation|| Average Compressive Strength|
Not less than, N/mm2
The standard modular or non-modular size of common building bricks shall be as follows:
TYPE OF BRICK LENGTH WIDTH HEIGHT
Modular Brick 190 mm x 90 mm x 90 mm
Modular Tile Brick 190 mm x 90 mm x 40 mm
Non Modular Brick 230 mm x 110 mm x 70 mm
Non Modular Tile Brick 230 mm x 110 mm x 40 mm
Selection of Bricks:
Brickwork shall be classified according to the class designation of bricks used.
Class of bricks to be used shall depend upon the strength requirements, availability of supports at sides and top, exposure conditions etc
|Use||Min Class of Bricks|
|Below Ground||Class 12.5|
|Un-plastered external walls, Plastered external |
walls subjected to severe climatic conditions
or toxic gasses and chemicals
|Plastered External Walls||Class 7.5|
|Un-plastered Internal walls||Class 7.5|
|Free standing walls, parapets||Class 12.5|
Brickwork shall be constructed in mortar prepared as specified herein. The mortar grade (proportion) shall be of minimum MM5 or as specified for a particular work.
Bricks shall be soaked in water such that water just penetrates the whole depth of the bricks. The soaked bricks shall be removed from water early enough to be skin-dry when laying.
Alternatively bricks may be adequately soaked in stacks by profusely spraying with clean water at regular intervals for a period not less than six hours. Soaked bricks shall be stacked on a clean place where they are not spoiled by dirt, earth and the like.
The period of soaking shall be found at site by a field test. The bricks shall be soaked in water for different periods and then broken to find the extent of water penetration. The least period that corresponds to complete soaking will be the one that shall be allowed for in construction work.
Bricks shall generally be laid in English Bond unless a different appearance at face is required as per Architectural requirements.
Half or cut bricks shall not be used except as closers to complete the bond. Closers in such cases, shall be cut to the required size and used near the ends of the wall. Header bond shall be used preferably in all courses in curved plan for ensuring better alignment.
Header bond shall also be used in foundation footings unless the thickness of walls (width of footing) makes the use of headers impracticable. Where the thickness of footing is uniform for a number of courses, the top course of footing shall be headers.
All loose materials, dirt and set lumps of mortar which may be lying over the surface on which brick work is to be freshly started, shall be removed with a wire brush and the surface wetted. Bricks shall be laid on a full bed of mortar. When laying, each brick shall be properly bedded and set in position by gently pressing with the handle of a trowel. It’s inside face shall be buttered with mortar before the next brick is laid and pressed against it. Joints shall be filled and packed with mortar such that no hollow space is left.
Walls shall be taken up truly in plumb or true to the required batter where specified. All courses shall be laid truly horizontal and all vertical joints shall be truly vertical. Vertical joints in alternate courses shall come directly one over the other. Quoin, jambs and other angles shall be properly plumbed as the work proceeds. Deviations shall be within maximum permissible tolerances as below:
Deviation from vertical within a storey shall not exceed 6 mm per 3 m height.
Deviation in verticality in total height of any wall of building more than one storey in height shall not exceed 12.5 mm.
Deviation from position shown on plan of any brick work shall not exceed 12.5 mm.
Relative displacement between load bearing wall in adjacent storeys intended to be vertical alignments shall not exceed 6 mm.
All quoins shall be accurately constructed and the height of brick courses shall be kept uniform. This will be checked using a graduated wooden straight edge or a storey rod indicating height of each course including thickness of joints.
The position of damp proof course, window sills, bottom of lintels, top of the wall etc. along the height of the wall shall be marked on the graduated straight edge or storey rod. Acute and obtuse quoins shall be bonded, where practicable in the same way as square quoins. Obtuse quoins shall be formed with squint showing three quarters brick on one face and quarter brick on the other.
The brick work shall be built in uniform layers. No part of the wall during its construction shall rise more than one meter in a day. Parts of wall left at different levels shall be raked back at an angle of 45 degrees or less with the horizontal. Toothing shall not be permitted as an alternative to raking back. For half brick partition to be keyed into main walls, indents shall be left in the main walls.
All pipe fittings and specials, spouts, hold fasts and other fixtures which are required to be built into the walls shall be embedded, as specified in their correct position as the work proceeds unless otherwise directed by the Engineer.
Top courses of all plinths, parapets, steps and top of walls below floor and roof slabs shall be laid with brick on edge, unless specified otherwise.
Brick on edge laid in the top courses at corner of walls shall be properly radiated and keyed into position to form cut corners. Where bricks cannot be cut into the required shape to form cut corners, cement concrete 1:2:4 (1 cement:2 coarse sand : 4 graded stone aggregate 20 mm nominal size) equal to thickness of course shall be provided in lieu of cut bricks.
Bricks shall be laid with the frog up. However, when the top course is exposed, bricks shall be laid with the frog down. For the bricks to be laid with frog down, the frog shall be filled with mortar before placing the brick in position.
In case of walls one brick thick and under, one face shall be kept even and in proper plane, while the other face may be slightly rough. In case of walls more than one brick thick, both the faces shall be kept even and in proper plane
Pipe sleeves shall be provided for taking service lines without excessive cutting of completed work. Such sleeves in external walls shall be sloped down outward so as to avoid passage of water inside
Top of the brick work in coping and sills in external walls shall be slightly tilted. Where brick coping and sills are projecting beyond the face of the wall, drip course/throating shall be provided where indicated.
Care shall be taken during construction that edges of jambs, sills and projections are not damaged in case of rain. New built work shall be covered with jute bags or tarpaulins so as to prevent the mortar from being washed away. Damage, if any, shall be made good to the satisfaction of the Engineer.
Vertical reinforcement in the form of bars, considered necessary at the corners and junction of walls and jamb opening doors, windows etc. shall be encased with cement mortar not leaner than 1:4 (1 cement: 4 coarse sand), or cement concrete mix as of 1:3:6 (1 cement: 3 coarse sand: 6 graded stone aggregate 20 mm nominal size). The reinforcement shall be suitably tied, properly embedded in the foundation and at roof level. The dia. of bars shall not be less than 8 mm.
In retaining walls and the like, where water is likely to accumulate, weep holes, 50 to 75 mm square shall be provided at 2 m vertically and horizontally unless otherwise specified. The lowest weep hole shall be at about 300 mm above the ground level.
The thickness of all types of joints including brick wall joints and cross joints shall be such that four courses and three joints taken consecutively shall measure as follows:
390 mm, in case of modular bricks.
310 mm, in case of non-modular bricks
The Specified thickness of joints shall be of 10 mm. Deviation from the specified thickness of all joints shall not exceed one-fifth of the specified thickness.