(D) BRICK MASONRY / STONE MASONRY WORK

Transcription

1 (D) BRICK MASONRY / STONE MASONRY WORK 1.0 INDIAN STANDARDS TO BE FOLLOWED ARE All relevant standards as specified elsewhere in this volume are also applicable. Indian standards to be followed are : IS : 1077 IS : 2185 IS : 2116 IS : 2212 IS : 2250 IS : 27 : Specification for common burnt clay building bricks. : Block Masonry : Specification f or sand for masonry mortar. : Code of Practice for Brick work. : Code of practice for preparation and use of masonry Mortars. : Handbook of method of measurement for building works. 2.0 MATERIALS 2.1 BRICKS Bricks shall be sound, hard, well-burnt, uniform in size, shape and colour, homogeneous in texture, giving a metallic ringing sound, free from flaws, cracks, holes, lumps or grit and sizes should be square, straight and sharply defined. They shall not break when struck against each other and dropped flat from a height of 1m to the ground. They shall conform to Table No. 1 (reproduced as table-2 of enclosed Annexure) of IS:1077 giving classes of common burnt clay bricks Bricks shall be as specified and detailed in the BOQ. It shall have to be approved prior to procurement. Bricks shall be obtained from an approved source and shall be of uniform

2 colour, size, shape. Bricks shall have smooth rectangular faces with sharp straight rectangle edges. Maximum absorption shall not be more than 15% of its dry weight on immersion in water for 24 hours. Minimum crushing strength shall be 35 kg/sq.cm. if not specified in the BOQ Bricks of approved quality and quantity shall have to be procured by the contractor at the desired time. No delay or extra cost due to non-availability shall be accepted. The contractor is obliged to carry out the work as specified. It shall be the responsibility of the contractor to procure sufficient quantities of bricks and stack them at site or elsewhere to avoid delays. 2.2 CEMENT Cement used shall be ordinary Portland Cement. 2.3 LIME Lime used shall conform to IS 712 specification for Building Limes. Filed slacking shall be done as per IS 1635 code of practice for field slaking of lime and preparation of putty. 2.4 WATER Water used for masonry shall be clean and free from injurious amounts of deleterious materials and shall conform to specification given in concrete and mortar section. 2.5 FINE AGGREGATE (SAND) Sand shall conform to IS 2116 specification for masonry mortars.

3 3.0 MORTAR Mortar shall be as specified under the respective item in the BOQ. Its preparation and material shall comply with concrete and mortar section of this volume. Mixing of mortar shall be done in mixture just before 30 minutes of laying. Maximum time allowed to use the mortar shall not exceed 30 minutes. 4.0 WORKMANSHIP 4.1 Bricks used for masonry in cement mortar shall be soaked by immersing in water. (so as to prevent bubbling) as least one hour prior to start of actual laying. 4.2 Bricks shall be laid in English bond unless otherwise specified. Half of cut bricks shall be used only for the purpose of bound and at no other place cut bricks shall be allowed in work. 4.3 Work shall be true to horizontal lines and perfect plumb. Vertical joints shall be truly vertical and those in alternate courses shall be in the same vertical line. Joints of each course shall be within the limit of 6 mm to 10 mm depending upon the size of bricks. Total height of 9cm brick with the 5 courses and 5 mortar joints shall be 50 cm. In no case shall joint thickness of horizontal and vertical be more than stated above. Joints should be filled to full depth and checked each time. Prior to start of work it must be noted and checked that bricks on top are full size bricks (flat or brick on edge). To achieve

4 this, precautions should be taken from the start of the first layer. Thickness of joints shall so adjusted so as to have full bricks on top. Also it must be noted and checked that all horizontal joints on every floor are at the same level, so as to allow proper bonding at junctions. Required datum levels must be established throughout the floor and only then should work start. It is equally important to take into account levels of window sills, lintels, etc. while finalizing courses and joint thickness. In normal practice architects to take care of these while finalizing levels, but it is difficult to expect the ideal situation at all places. In such situation, the decision of the EIC shall be taken and in providing brick on edge, concrete sills, etc. In addition, for convenience and speed, gauge boards of exact width shall be fixes at the edges of masonry to correct line and plumb. Theses boards shall be marked with course levels to achieve exact height of each course and full bricks at the top. 4.4 One or half brick thick wall shall have minimum one face in true plumb. 4.5 It is imperative to raise the bricks work uniformly over complete work jointed together. If this is not possible, racked brick work shall be done at 45 degrees to the vertical. To thing shall not be accepted.

5 4.6 All iron fixtures, pipe outlets, hold-fasts for doors and windows shall be fixed when the brick work is in progress. It must be embedded in concrete as specified or as directed by the EIC. Required treatment to fixtures shall be carried out prior to embedding. 4.7 To achieve better results and proper working, the following tools should be available with masons working at site. 1. Sprit level. 2. Wooden/Aluminum straight edge : 3 m long meter steel tape. 4. Right angle ½ meter long. 5. Line and pin strings. 6. Plumb 7. Storey rods. 4.8 Joint thickness shall be provided as discussed above. Joints shall be filed to full before second course is laid. Frogs shall be upward at all times. Joints shall be raked back to a minimum 10 to 15 mm while the mortar is wet. Surface of brick work shall be cleaned with coil string, wire brushes, etc. to keep the surface free for the next operation. All dropped and spoiled mortar, brickbats, etc. shall be cleared from the floor before work is closed for the day. 4.9 PROTECTION AND CURING Wet work shall be protected from rains by suitable covering. Masonry in cement or cement-lime mortar shall be kept constantly moist on all the faces for a minimum period of ten

6 days. The top of masonry shall be left flooded with water at close of the day. In case of brick work in lime mortar, curing shall commence two days after laying of masonry and shall continue for the next seven days Scaffolding independent of brick work i.e. double scaffolding shall be provided. It should be tied to brick work or structure at suitable intervals in both directions. Two rows of plank shall be provided all around. Planks shall be at least 50 mm thick and well-tied to scaffolding. Railing to the outside face shall be provided. While erecting scaffolding, the following points must be noted and closely followed. 1. Minimum number of holes in the horizontal direction. Holes shall be formed be omitting header brick. 2. No holes in pillars under 1 meter in widh. 3. No holes near the skew backs of arches, 4. Scaffolding must be sound and strong and easy to maintain. 5. Holes left must be closed while finishing the plaster. 5.0 TYPES OF BRICKS WORK 5.1 Walls 230 mm thick or more Walls of 230 mm thickness or more shall be constructed with approved and selected bricks. Mortar shall be as specified in the BOQ. Points discussed above shall be followed for workmanship.

7 Brick wall of 230 mm thickness shall be constructed from one side and one face shall be true and plumb. Thicker walls shall be constructed with masons on both faces and both the faces shall be true and plumb Measurements shall be in cubic meters. 5.2 Half brick work plain or reinforced mm thick brick work shall be called as half brick work. It shall be built by laying bricks in stretcher bond. Mortar shall be as specified in the BOQ. These walls may be used for forming cavities or partition wall inside building. Brick work shall reinforced with 6 mm M.S. dia bars, 2 bars at every third layer. Other reinforcing materials such as GI metal lath GI hoop iron 25mm x 1.6 mm shall be used at every third layer as detailed by the manufacture. Embedding or reinforcement shall be done very carefully. All precautions shall be taken so that edges are not exposed. Lapping of bars and lath shall be proper and staggered Measurement shall be in square meters. Reinforcement shall not be measurement separately DEDUCTIONS All the deductions shall be made as per the IS : 1200 (Part-III & IV) unless otherwise mentioned. 6.0 RATE 6.1 The rate shall include the cost of all the materials and labour as described in their respective items of work and for all the operations as detailed in the respective specifications for the

8 various items of work. Brick on edge courses, cut brick corners, splays, reveals, cavity walls, shall be included in BRICK WORK for the purpose of payment. 6.2 The following operations shall be included in the rate for BRICK WORK. a. Raking out joints for plastering or for pointing done as a separate process or for finishing joints flush as work proceeds. b. Preparing tops and sides of existing walls and the like for raising. c. Rough cutting and waste for forming gables, cores of arches, splays at leaves and the like and all rough cutting in the body of brick-work, unless otherwise stated. d. Plumbing to angles and battered surfaces. e. Forming reveals to jambs where fair cutting on exposed faces is not involved. f. Leaving holes for pipes, etc. g. Building-in holdfasts, air bricks, fixing bricks, etc. h. Building-in ends of beams, joists, slabs, lintels, sills trusses etc. i. Forming opening and flues for which no deductions is made. j. Bedding wall plates, lintels, sills, roof tiles, corrugated sheets, etc. k. Leaving chases of section not exceeding 50 cm in girth.

9 SECTION IV C MASONRY WORK STONE MASONRY 1.0 INDIAN STANDARDS Work shall be carried out to Indian Standards and Code of Practices. In absence International Standards shall be followed. These shall be latest issue. List given hereunder is not to be considered as conclusive and is for reference and guidance only. Any discrepancies / conflict noticed shall be directed to the EIC for his direction/approval. However as a general rule more stringent specification shall take precedence. (1) IS 1121 Methods of test for determination of strength properties of natural building stones. Part 1 Compressive strength Part 2 Transverse strength Part 3 Tensile strength Part 4 Shear strength (2) IS 1124 Methods of test for determination of water absorption apparent specific gravity and porosity of natural building stone. (3) IS 1127 Recommendations for dimensions and workmanship of natural building stones for masonry work. (4) IS 1489 Specification for Portland Pozzolana cement (5) IS 1597 Code of Practice for Part 1 construction of stone masonry : Rubble stone masonry (6) SP 27 Handbook of method of measurement of building works. 2.0 MATERIAL 2.1 Cement Cement shall be ordinary Portland cement conforming to IS. Approved blended cement shall be used for internal plaster,

10 masonry, flooring, waterproofing and plumbing works. For all RCC and PCC works, approved fly ash shall be used. For external plaster approved fly ash as per specification of item shall be used It shall be received in bags of 50 kg (or in bulk carriers in case of storage in silos) and each batch shall be accompanied with a test certificate of the factory. Also it shall be tested before use to ascertain its strength, setting time, etc. In case cement has been stored for over 6 months from date of manufacturer or for any reasons the stored cement shows signs of deterioration or contamination, it shall be tested as per the direction of the EIC prior to use in the works. 2.2 Fine aggregate Natural sand deposited by stream or glacial agencies as a result of disintegration of rock is the best form of fine aggregate. The fine aggregate shall conform to following standards. (i) For plain and reinforced concrete IS 383 Specification for coarse and fine aggregates from natural sources for concrete. (ii) Mortar and grout IS 2116 Specification for sand for masonry mortars. (iii) For plastering IS 1542 Specification for sand for plaster (Class A grading) Sea sand should not be used unless approved by the EIC. If approved, the required treatment shall be done at the contractor's cost Sand shall be hard, durable, clean and free from adherent coatings and organic matter and shall not contain any appreciable amount of clay. Sand shall not contain harmful impurities such as iron, pyrites, coal particles, lignite, mica shale or similar laminated material, alkali, and organic impurities in such form or quantities as to affect the strength or durability of concrete or mortar. Also it should not contain any material liable to attack the steel reinforcement.

11 When tested as per IS 2386 Part I and Part II, fine aggregate shall not exceed permissible quantities of deleterious materials Fine aggregate shall be thoroughly washed at site with clean fresh water such that the percentage of all deleterious material is within the permissible limits laid down Aggregate shall be stored in such a way that it does not get mixed with mud, grass, vegetables and other foreign matter. The best way is to have a hard surface platform made out of concrete, bricks or planks. It should be to the approval of the Engineer. 2.3 Water Water used for mixing and curing shall be clean, reasonably clear and free from objectionable quantities of silt, oils, alkalis, acids, salts so as not to weaken mortar, or concrete or cause efflorescence or attack the steel in RCC While curing. It shall be free of elements, which significantly affects the hydration reaction or otherwise interferes with hardening of concrete during curing, or those elements which produce objectionable stains or deposits. Potable water is generally satisfactory but it shall be tested prior to use in the works Water tested shall be in accordance with IS Maximum permissible limits of deleterious materials in water as given in IS Stone Stone to be used in masonry shall be trap, granite, quartzite, gneiss, laterite or any other type of good stone as specified or as approved by the Engineer. For all practical purposes good trap, granite, quartzite or gneiss shall be used unless specified All stones shall be free from defects like cavities, cracks, sand holes, flaws, injurious veins, patches of loose or soft materials, etc. The percentage of water absorption shall generally not exceed 5% The strength of building stones should be adequate to carry the loads imposed. Table 1 of IS 1597 gives the minimum crushing strength of approved stones. Minimum strength shall be 200 kg/sqcm unless specified otherwise.

12 2.4.4 Stones used shall be small enough to be lifted and placed by hand. Length of the stones shall not exceed three times their height, and the breadth of the base shall not be greater than three-fourths of the thickness of wall or less than 150 mm. The height of stones for rubble masonry may be upto 300 mm Stones with round faces shall not be used. 2.5 Metal fittings Metal fittings shall be non-corrosive/non-ferrous. Use of iron clamps and similar fittings for embedding into the masonry work shall be avoided. If permitted by the Engineer, they shall be treated with anti-corrosive treatment. 2.6 Mortar The cement, sand and water used shall meet the Indian Standards specifications Mortars shall be prepared by mixing fine graded aggregate with cement in the proportion specified for respective items of work as detailed in the Schedule- A. Mixing of mortars shall be done by mechanical mixers or by hand mixing. Hand mixing shall not be permitted Mortars shall be specified by proportion. Volumetric mixing shall be based on dry volumes of each ingredient. For convenience, measurement shall correspond to volume of one cement bag i.e cu m. Boxes shall be of size 40 X 35 X 25 cm. These shall be marked as mortar mixing boxes by red paint and shall be used throughout the contract. Mechanical mixing proportions shall be done with the use of these boxes Cement mortar shall be prepared by mixing cement and sand in specified proportions. Proportioning shall be carried out as detailed above. Sand shall be added suitably to allow for bulkage if required. Bulkage shall be determined as specified in IS 2386 Part III. Cement and sand added to mixer shall be thoroughly mixed and water shall be added to it gradually. After addition of water the mixer shall run for a minimum of 3 minutes. The mortar mixed shall be consumed within 30 minutes of its mixing. 3.0 WORKMANSHIP

13 3.1.1 Dressing and shaping of stone shall be done before being used in masonry. Quality of dressing and shaping shall be as approved by the Engineer All necessary chases for joggles, dowels and cramps should be formed in stone beforehand Sufficiently wetted, cleaned stone shall be laid to lines, levels, curves and shapes as shown in the plans. Stones shall be laid on their broadest face in mortar and settled carefully in place with a wooden mallet. Clean chips and spells, carefully selected to fit in the spaces shall be wedged to avoid thick beds or joints of mortar. 3.2 All connecting walls shall be raised together. In case one part is required to be left behind, raking back at an angle of 45 degrees or less shall be done. 3.3 It is imperative to adjust levels right at the start to achieve correct levels of window sill, roof, etc. But as this is quite difficult to achieve, it shall be part of the stone masonry work to provide cement concrete sill of mix in a ratio of 1:4:8 (1 cement, 4 sand and 8 20 mm graded aggregate) of 100 to 150 mm thickness in consultation with the Engineer. 3.4 Maximum thickness of joint shall be 20 mm for random rubble and 10 mm for course. Stones shall be set and laid by wooden hammer (mallet) and voids, if any, packed and consolidated by stone chips. Chips used shall not be more than 15% by volume of masonry. 3.5 Stones of full width of wall thickness shall be provided at every 600 mm centre to centre in each layer and staggered. For walls thicker than 600 mm two through stones overlapping each other at a minimum of 150 mm shall be placed. 3.6 The work shall be in perfect plumb or battered as specified. 3.7 Corner stones shall be well-dressed and chiseled. These shall be laid header and stretcher alternate. They shall not be smaller than cu m and 300 mm in length. Further it must be noted that 25% of the above shall not be shorter than 500 mm in length. 3.8 Jambs shall be made from dressed corner stones.

14 3.9 Work of the day shall be raked to a depth of 20 mm while the mortar is green and cleaned with a coired string brush or wire brush. Stone surfaces shall be free of mortar or cement coats Vertical joints shall be staggered At angular junctions, stones at each alternate course shall be wellbonded into the respective courses of the adjacent wall Masonry construction with very thin faces, tied up with occasional through stones or filled up with dry packing or small-size aggregates shall be strictly prohibited Storey rods showing the heights of all doors and windows and other necessary information should be used at the time of construction of masonry Door and window frames shall be fixed with hold-fast of adequate size and strength. Iron hold-fast shall be treated with anti- corrosive coating and timber to prevent attack from insects and termites. In addition, hold-fast shall be securely embedded in chases with cement-concrete in a ratio of 1:2:4. Frames shall preferably be fixed simultaneously as work proceeds. 4.0 SCAFFOLDING 4.1 Scaffolding, independent of masonry work i.e. double scaffolding, shall be provided. It should be tied to masonry work or structure at suitable intervals in both directions. Two rows of planks shall be provided all around. These shall be at least 50 mm thick and welltied to the scaffolding. Railing to outside faces shall be provided. While erecting scaffolding, the following points must be noted and closely followed. 1. Minimum number of holes in horizontal direction. Holes shall be formed by omitting header. 2. No holes in pillars under 1 metre in width. 3. No holes near the skew backs of arches. 4. Scaffolding must be sound and strong and easy to maintain.

15 4.2 Protection and Curing Green work shall be protected from rains by suitable covering. Masonry in cement or composite mortar shall be kept constantly moist on all the faces for a minimum period of seven days. The top of masonry shall be left flooded with water at close of the day. Care shall be taken not to disturb or wash out green mortar. In case of stone work in lime mortar, curing shall commence two days after laying of masonry and shall continue for the next seven days. 5.0 TYPES OF STONE MASONRY Uncoursed / Random Rubble Masonry Masonry constructed by selecting stones from quarry, more or less at random, of all sizes and shapes. Cutting of stones restricted to remove inconvenient corners with scabbling or spelling hammer Construction 1. Individual stones shall have thickness and width of not less than 150 mm and length not less than 1.5 times its height. Stones shall be dressed with a mason's hammer by knocking off weak corners and edges. Face stone shall be so dressed that bushing on the exposed face shall not project by more than 40 mm from the general wall surface. In case plastering is to be done, projection shall be limited to 19 mm and depression to 10 mm. 50% stone shall be cu m (10 litres) in walls upto 500 mm. Walls thicker than 500 mm shall have 50% stone bigger than cu m (15 litres). 2. Bond or through stones shall be 2 pieces (nos.) per sq m, face area shall be 0.03 sq m and for full width of masonry for walls upto 600 mm stones shall be marked distinctly.

16 3. For massive work with a width of a metre and above, vertical headers 450 mm long or with a depth of two courses whichever is more shall be provided at the rate of one for every sq m of area in the plan. 4. Quoins (corners) shall be dressed square to the face and rough tooled to 100 mm from face, and vertical joints dressed to 40 mm from face. No quoins shall be smaller than cu m in volume and they shall also not be less than 300 mm in length, 25% of them being not less than 500 mm in length. 5. Hearting stone shall not be less than 150 mm in any direction. In walls upto 500 mm a minimum of 30% stone shall be cu m (10 litres). For thicker walls minimum 30% stone shall be cu m (15 litres). 6. The jambs shall be made with stones specified for quoins except that stones provided on the jambs shall have their length equal to the thickness of the wall. For walls upto 600 mm, a line of headers shall be provided as specified for bond. 7. A plum stone at about 900 mm intervals shall be provided. 8. Stones shall be laid with or without courses as specified. Quoins shall be laid header and stretcher alternatively. Laying shall be carefully done to form neat and close joints. Face stone shall extend and bond well in the back. These shall be arranged to break joints. 5.2 Coursed Masonry Course walling shall be built in courses which may vary in height from 150 mm to 400mm but the stones in any one course shall roughly be square and of the same height.

17 5.2.1 Construction 1. Stones received from quarry shall be dressed to have the vertical and horizontal sides perfectly straight, parallel and at right angles to adjacent sides. Bushing on the face shall not project more than 40 mm. Beds and tops shall be tooled at least 100 mm from the face. Faces of vertical joints shall be square to the face and rough tooled at least 50 mm from the face. 2. Stones shall be longer in breadth than in height and shall run back into the masonry not less than 1.5 times the height. 30% of the stones shall have tailing twice their height. Further 30% of these face stones shall not be less than 0.02 cu m or 20 litres. The height shall not be less than 150 mm or as specified in the pattern in the drawing. 3. Hearting stones shall consist of flat bedded stones, carefully laid on their proper beds in mortar, chips and spells of stone, avoiding excess use of mortar and hollow spaces in masonry. These shall be limited to 10% in the first sort and 15% in the second sort. 30% of the stones shall not be less than cu m or 10 litres for walls 500 mm or less in thickness. For walls thicker than 500 mm, 30% of them shall not be less than cu m or 15 litres. 4. Quoins (corner) stones shall be twice their height or minimum 440 mm long whichever is more and shall be of the same height as that of the course. They shall be laid alternately as stretcher and header. 5. Through stones shall be a minimum 450 mm long and shall be 180 mm centre to centre for every course. They shall be about 0.05 sq m in face area and 0.03 sq m in average cross sectional area. For thicker walls (above 600 mm) they shall over-lap by at least 150 mm.

18 6. Thickness of joint shall be maximum 10 mm. When pointing is to be done, joints shall be raked to a depth of not less than 10 mm while the mortar is green. 6.0 Item includes 6.1 The various items shall include the cost of the followings a) Material and labour for proper execution as per specification and site requirement including temporary erections like scaffolding, centering, shuttering and removal of the same. Curing and protection shall also be included as directed. b) Racking out of joints and cleaning of stone surfaces. c) Preparing tops and sides of existing walls. d) Bond stones. e) Making grooves and rebates in the adjoining work for fixing jali. f) Extra labour involved in dressing of corner stones and jambstones wherever required. g) Making holes, openings, outlets, etc. embedding pipes, ends of beams, joists, slabs, trusses, sills, etc. whatever required during construction and neatly finishing the exposed surfaces and opening as per instructions of the EIC. Signature of Tenderer Date.: Additional Engineer(I&NT) Date.: Chief