1. Cement
1.1 The cement, unless otherwise described, shall be Ordinary Portland Cement complying with MS 522 and as specified under SECTION D: CONCRETE WORK.
2. Sand
2.1 Sand for mortar shall comply with MS 29 and as specified in SECTION D: CONCRETE WORK.
3. Mortar
3.1 Mortar shall consist of one (1) part of cement to six (6) parts of sand, with the addition of an approved mortar plasticiser used strictly in accordance with the manufacturer's instructions. The ingredients for mortar shall be measured in proper gauge boxes and shall be mixed on a clean boarded platform or in an approved mechanical batch mixer. 3.2 All mortar shall be used within 45 minutes of mixing and no remaking up of mortar shall
be permitted thereafter.
3.3 Mortar for brickwork below damp proof course or ground floor level shall be in the proportion of one part of cement and three parts of sand.
4. Bricks and Blocks
4.1 Samples
Separate samples of each type of bricks and blocks taken at random from the load, shall be submitted to the S.O. for approval before the bricks and blocks are used. All subsequent deliveries shall generally be up to the standard of the samples approved. No soft, broken, twisted or otherwise defective bricks and blocks will be permitted to be used. 4.2 Clay Bricks
All ordinary clay bricks shall be machine-made and wire cut complying with MS 76 and shall be hard, well burnt, sound, square and clean.
4.3 Cement Sand Bricks and Hollow Blocks
4.3.1 All cement sand bricks and hollow blocks shall comply with MS 27.
4.3.2 Size
Cement sand bricks shall be of a nominal size as given below:
Length(mm) Width(mm) Depth(mm)
225 ± 3.2 113 ± 1.6 75 ± 1.6
Dimensional tolerances for hollow blocks shall be ± 3mm on all faces. The shell of each hollow block shall be 38mm thick minimum on all sides.
4.3.3 Composition
Cement sand bricks and hollow blocks shall consist of an intimate and uniform mixture of sand and cement. The sand and cement shall be mixed in the ratio of six (6) parts of sand to one (1) part of cement by volume in a mechanical mixer capable of taking one (1) bag of cement (50kg of cement shall be taken as 0.035 cube). The sand used shall be as described hereinbefore and the maximum size shall pass through a 4.8mm mesh BS sieve. The cement used shall be Ordinary Portland Cement as described under SECTION D: CONCRETE WORK.
4.3.4 Supply
The Contractor shall only use cement sand bricks and hollow blocks supplied by approved manufacturers.
4.3.5 Compressive Strength
The minimum permissible average compressive strength shall be 5.2N/mm sq. for bricks and 2.8 N/mm sq. for hollow blocks per 10 samples taken at random from the Contractor’s stock pile of 1000 or part thereof. All rejected or condemned bricks shall be removed from the Site at the Contractor's expense. 4.4 Autoclaved Aerated Concrete Block
4.4.1 Autoclaved aerated concrete blocks shall be high pressure steam cured consisting of a mixture of ordinary cement, sand and lime. The mix shall be free of asbestos or toxic substances.
4.4.2 Where autoclaved aerated concrete blocks are used in lieu of clay bricks, the equivalent thickness shall be as below: -
Thickness of Brickwall Thickness of Autoclaved Aerated Concrete Blockwall
Half Brickwall 100mm thick One Brickwall 200mm thick
4.4.3 The autoclaved aerated concrete blocks shall have the following performance criteria: -
(a) dry density of between 500kg/m3 and 700kg/m3; (b) dimensional accuracy of ± 1.5mm on all faces;
(c) the minimum permissible compressive strength shall be 2.5 N/mm sq. per 10 samples taken at random from the Contractor’s stock pile of 1000 or part thereof.
(d) minimum fire rating of two (2) hours. 4.5 Patented Block
Patented blocks shall comply with MS 27 and shall be used strictly in accordance with the manufacturer’s instructions.
5. Walling
5.1 Brick Walling
5.1.1 The whole of the brickwork shown in the Drawings, unless otherwise specified, shall be constructed with standard size clay bricks in mortar as described and leave the surface ready for plastering.
5.1.2 Notwithstanding paragraph 5.1.1 above and anything else to the contrary elsewhere contained in the Drawings and/ or Bills of Quantities, the Contractor may with approval of the S.O. construct all non load bearing brickwork above damp proof course or ground floor level and which will be plastered on both sides, with cement sand bricks thereinbefore specified. Provided always that in the event of the S.O. allowing the substitution of clay bricks with cement sand bricks, a deduction shall be made from the Contract Sum for such substitution at rates to be derived from the prices to Site of clay bricks and cement sand bricks, and the average size of the clay bricks and cement sand bricks concerned, using the formulas shown in APPENDIX E1.
5.1.3 All clay bricks shall be soaked in a suitable tank or pit to be provided by the Contractor for at least half an hour before being laid and shall be kept wet whilst being laid. The top of walls left off shall be thoroughly wet before work is resumed. All constructed walling must be left wet and properly protected from the direct sunlight during the following day. The Contractor shall provide sufficient means to ensure that this is done.
5.1.4 Cement sand bricks shall not be soaked but dipped in water before being laid and all constructed brickwork shall be protected from direct sunlight during the day on which it is laid and also during the following day and the Contractor shall provide sufficient means to ensure that this is done.
5.1.5 All bricks shall be properly bedded in mortar and all joints shall be thoroughly flushed up and raked out to a depth of 13mm as the work proceeds. No joint shall exceed 10mm in thickness.
5.1.6 Brickwork shall be carried up perfectly true and plumb in a uniform manner. No one portion being raised more than 1m above another at one time. No overhand work shall be permitted and scaffolding shall be carried up as the work proceeds. The vertical points of every alternate course shall be kept perpendicular over one another, and all perpends, quoins, etc. shall be kept strictly true and square. 5.1.7 All intersections and angles of walls shall be properly bonded together, and all
walls and piers of lengths and widths not multiples of brick sizes shall be cut and bonded in the best approved manner. No broken bricks shall be used except where required to form bonds.
5.1.8 All half brick (113mm) walls and partitions shall be reinforced at every fourth course with approved brick reinforcement commencing two courses above floor level. For block walling, reinforcement shall be at every second course commencing one course above floor level.
5.2 Hollow Block Walling
5.2.1 The cement sand block wall shall be laid in the manner specified for brickwall. The hollow block shall not be soaked but dipped in water before laying. The hollow block wall shall be reinforced at every second course with reinforcement commencing one course above floor level.
5.3 Autoclaved Aerated Concrete Block Walling
5.3.1 Where shown in the Drawings and/ or described in the Bills of Quantities or as alternative to clay bricks, the Contractor may use autoclaved aerated concrete blocks for non load bearing walls and partitions. The autoclaved aerated concrete block work shall be constructed strictly in accordance with the manufacturer’s instructions. Any extra cost in connection therewith shall be borne by the Contractor.
5.3.2 The autoclaved aerated concrete block work shall be installed using an approved thin layer of adhesive mortar to all horizontals and perpends. The first course must be made true and level using a normal layer of mortar with thin layer of adhesive to fully seal the perpends. The thin layer of adhesive shall be applied using a notched trowel to obtain an even distribution of adhesive to achieve joint thickness of 2-3mm.
5.3.3 A damp-proof course slip-joint membrane shall be laid on top of floor slab or beams before receiving the mortar bedding to allow for differential movement between the blocks and the supporting structure.
5.3.4 The autoclaved aerated concrete block work shall be laid in a manner that the vertical joint of the lower course shall be staggered at least 100mm relative to the vertical joint of the overlaying course.
5.3.5 Unless otherwise directed and/or shown, where concrete block walls abut concrete faces, the face shall be flushed.
5.3.6 Control joints should be built into walls at spacing not greater than 8.0 meter centres, and at locations in accordance with the manufacturer’s recommendation.
5.3.7 Care must be taken to keep the walls clean, strictly in accordance with the manufacturer’s recommendation. Excess adhesive must be removed progressively.
5.3.8 In lieu of cement sand plastering, the wall surfaces may be finished with suitable surface coating that has the dual properties of being waterproof and water vapour permeable and shall be applied in accordance with the manufacturer’s recommendation.
6. Bond
6.1 All half brick walls shall be built in Stretcher Bond.
6.2 All other brickwork shall be built in English Bond or as shown in the Drawings.
7. Damp Proof Course
7.1 Unless otherwise shown in the Drawings, bituminous sheet damp proof courses shall comply with BS 8215 laid in brickwork on a level bed of cement mortar (1:1) and coated on the upper surface with hot bitumen and lapped at least 150mm at angles and joints. 7.2 In all cases of doubt as to the exact location of the damp-proof course the Contractor
8. Building in Cramps
8.1 Unless otherwise shown in the Drawings, cramps for frames, metal windows and precast units shall be built in at 1m centres on the vertical side of the frame. Mild steel cramps shall be 25mm x 3mm x 225mm long for fixing wooden frames, etc. One end of the cramp shall be turned up and screwed to back of the frame and the other end shall be split and fish-tailed for building in. Cramps which are to be fixed to concrete shall be embedded in concrete and built into brickwork as the work proceeds.
9. Scaffolding
9.1 All scaffolding shall be carried up as the work proceeds and shall be safe for use.
10. Facing Brickwork
10.1 All facing brickwork shall be executed in first quality approved facing bricks in Stretcher or Flemish Bond as shown in the Drawings, properly bonded into any backing walls, piers, etc. Joints shall be raked out to a depth of 13mm and point up in coloured cement mortar to approved tints, finished with a neat struck weathered joint.
10.2 Facing brickwork shall be kept perfectly clean and no rubbing down of brickwork will be allowed.
11. Cutting
11.1 All arches, cuttings, sinks, setbacks, and projections shall be properly formed. Chases and holes through walls and slabs for the passage of pipes, wiring and the like shall be neatly cut or formed.
12. Stonework
12.1 Unless otherwise shown in the Drawings or described in the Bills of Quantities, all stone blocks used shall be of limestone or granite whichever is more readily available within the locality of the Site and shall be free from cracks, fissures or other defects to the approval of the S.O. The stone blocks shall in general, have their largest faces parallel. Unless otherwise required, the maximum thickness of the stone blocks shall in no case exceed the thickness of the wall or portion of the structure into which it is being built.
12.2 Stone walling shall be laid random uncoursed or random coursed as shown in the Drawings. Through or bonded stones shall be used at one stone per metre square for random uncoursed work, and two stones per metre square for random coursed. Where backing brickwall is shown, the through stone shall be properly bonded in such brickwall. 12.3 Unless otherwise shown in the Drawings, all stonework shall be bedded in cement and sand mortar (1:3) mix and finished with a flushed joint rubbed down with sacking. All interstices between individual stone shall be filled with mortar. Finish to exposed surfaces or random walling shall be hammer-dressed.
APPENDIX E 1