Building Materials and Construction
Building Materials and Construction is a large theory block. It asks you to identify, classify and specify materials such as stone, brick, lime, cement, timber, steel, tiles and paints, and then to describe how they are assembled into foundations, walls, floors, roofs, stairs and finishes.
Bricks
An IS 1077 modular brick is 190 x 90 x 90 mm; with a 10 mm mortar joint the nominal size becomes 200 x 100 x 100 mm. First-class bricks are table moulded, kiln burnt, sharp edged, ring when struck, and absorb not more than about 20 percent water.
Cement and mortar
OPC grades 33, 43 and 53 denote the 28-day compressive strength in N/mm2. PPC contains fly ash or slag; it gives better durability and lower heat of hydration but slower early strength. Cement mortar 1:4 to 1:6 suits masonry; 1:3 to 1:4 suits plaster.
Worked example: bricks in one cubic metre
Volume of one brick with mortar = 0.200 x 0.100 x 0.100 = 0.002 m3. Number = 1 / 0.002 = 500 bricks. For 10 m3 of brickwork, 5000 bricks; adding 5 percent breakage gives 5250 bricks. Using the actual 190 x 90 x 90 size would wrongly suggest about 640 bricks.
Construction elements
- Foundation: spread footing for ordinary soil, raft for weak soil, piles where the firm stratum is deep.
- Bonds: English bond has alternate header and stretcher courses; Flemish bond alternates header and stretcher within the same course; stretcher bond is for half-brick walls.
- Stairs: riser 150-190 mm, tread 250-300 mm, width at least 900 mm, headroom at least 2.1 m.
- DPC: 40-50 mm cement concrete 1:1.5:3 with waterproofing compound at plinth level.
Traps
- Mixing nominal and actual brick size when computing quantities.
- Applying a dry-volume factor of 1.33 to mortar but forgetting it for concrete.
- Saying English bond has headers in every course; it alternates courses.