Detailed specification of brick work in 1:4 mortar

Detailed specification: brick work in cement sand mortar 1:4

1. Scope: Providing and constructing brick masonry in superstructure/foundation in cement sand mortar 1:4 (1 part cement : 4 parts sand by volume), complete as per drawings and instructions of the engineer.

2. Materials

• Bricks: first-class, well burnt, uniform in colour, shape and size (typically 240 × 115 × 57 mm in Nepal), with sharp edges, giving a metallic ring when struck. Compressive strength as specified (first-class bricks normally not less than about 10 N/mm², and in no case less than 3.5 N/mm², the NBC minimum); water absorption not more than 20% after 24 hours; free from cracks, lime lumps and salts. Bricks are soaked in clean water for at least 2 hours (until bubbles stop) before laying.
• Cement: OPC 43 grade or PPC conforming to NS/IS, fresh and free from lumps; stored in a dry store on a raised platform.
• Sand: clean, hard, coarse river sand, free from clay, silt, mica, organic matter and salt; fineness modulus 1.5–2.5; silt content < 4%.
• Water: clean, potable, free from oil, acid, alkali and organic matter.

3. Mortar: Cement and sand are measured in boxes by volume (1 : 4), dry-mixed to a uniform colour, then mixed with the minimum water for a workable consistency. Mixing is done on a clean watertight platform or in a mixer. Only the quantity that can be used within 30 minutes is mixed; mortar that has begun to set is not retempered or used.

4. Workmanship

• The foundation bed is cleaned, levelled and wetted.
• The work is laid in English bond (or the bond shown in the drawing), with full headers and stretchers, and the vertical joints of alternate courses kept in line (perpends) to maintain plumb.
• Bricks are laid frog up, pressed into a full bed of mortar, and all joints are completely filled.
• Mortar joints are 10 mm thick (not more than 12 mm). The face joints are raked 12–15 mm deep while the mortar is green if the wall is to be plastered, or finished flush/struck if pointing is specified.
• The walls are raised uniformly, by not more than 1 m in one day; the work is kept plumb and level with a plumb bob, spirit level and line, and the surface is checked with a straight-edge.
• Where the work has to be stopped, it is raked back (stepped) according to the bond; toothing is left only where future extension is planned, with the engineer's approval.
• Openings, lintels, sills and the bearings of beams are as per the drawing; holes for services are provided.

5. Curing and protection: The brickwork is kept wet for at least 7 days by sprinkling, and protected from sun, rain and damage.

6. Tolerance and testing: Deviation from plumb should not exceed 5 mm per 3 m height, and wall thickness should be within ±5 mm. Samples of bricks (compressive strength, absorption) and mortar cubes may be tested as the engineer instructs.

7. Measurement and payment: The work is measured in cubic metres of finished masonry, to the net dimensions as built, deducting openings and other voids larger than 0.1 m²; there is no separate payment for scaffolding, curing and cleaning. Payment is at the contract rate per m³, which includes all materials, labour, tools, scaffolding, curing and wastage.