Masonry is a composite material used in construction of walls, both load bearing and non-load bearing. The composite consists of masonry unit, which can be brick, block (hollow or solid), rubble, dressed stone etc. laid in mortar. The mortar can be mud mortar, lime mortar, cement-sand mortar or any other combination mortar. Masonry is quantified by volume (in cu m). Sometimes, partition walls constructed of half brick thick masonry or brick laid on edge are quantified on area basis. Masonry in foundation and basement is distinguished as a separate item as compared to masonry in superstructure. The main reason for this is that construction of masonry in superstructure requires scaffolding. In addition, openings for doors, windows, ventilators etc. have to be left.
Deduction for Openings, Bearing etc. in Masonry
The quantity of masonry 1s first calculated considering it as a solid mass. Openings are subsequently deducted. There are certain conventions for such deductions. The principle is that very small openings and openings with unconventional shape are not deducted in order to compensate the additional involved in leaving such openings during construction.
No deduction is made for the following :
Opening each up to 1000 sq cm or 0.1 sq m (1 sq ft).
End of beams, purlins, posts, rafters etc. up to 500 sq cm or 0.05 sq m (72 sq inches) in section.
Bed plate, waIl plate, bearing of chajjas and the like up to 10 cm (4") depth.
Bearings of floor and roof slabs are de 'ucted from masonry. For other openings deductions are made in the following manner:
Rectangular Openings
Full deduction is made as under :
Deduct (b x h x thickness of wall)
where, b is the width of opening and h is the height of opening.
Segmental Arch Openings
For small segmental arches, deduction is made for the rectangular portion only up to the springing point. The segmental portion is considered as solid.
For large segmental arch openings, deductions is made for the whole openings -the rectangular portion, as well as the segmental portion.The area of segmental portion is obtained approximately by taking 2/3 of the span x rise x thickness of wall.
Thus, the total deduction =[(1 x h ) +((2/3)xlxr))]xthickness of wall where, I is the span of the arch/width of opening.'
Semi-circular Arch Openings
The area of semicircular portion = (1/2)llr2
The area of the semi-circular portion may also be obtained approximately by 314 x span x rise.
Thus, the total deduction =[(1 x h ) +((3/4)xlxr))] x thickness of wall Elliptical arches may be considered as semi-circular and may be dealt in same manner. For large arches, the actual area of opening shall be calculated correctly by mensuration formulae, and deducted.
Deduction for Openings, Bearing etc. in Masonry
The quantity of masonry 1s first calculated considering it as a solid mass. Openings are subsequently deducted. There are certain conventions for such deductions. The principle is that very small openings and openings with unconventional shape are not deducted in order to compensate the additional involved in leaving such openings during construction.
No deduction is made for the following :
Opening each up to 1000 sq cm or 0.1 sq m (1 sq ft).
End of beams, purlins, posts, rafters etc. up to 500 sq cm or 0.05 sq m (72 sq inches) in section.
Bed plate, waIl plate, bearing of chajjas and the like up to 10 cm (4") depth.
Bearings of floor and roof slabs are de 'ucted from masonry. For other openings deductions are made in the following manner:
Rectangular Openings
Full deduction is made as under :
Deduct (b x h x thickness of wall)
where, b is the width of opening and h is the height of opening.
Segmental Arch Openings
For small segmental arches, deduction is made for the rectangular portion only up to the springing point. The segmental portion is considered as solid.
For large segmental arch openings, deductions is made for the whole openings -the rectangular portion, as well as the segmental portion.The area of segmental portion is obtained approximately by taking 2/3 of the span x rise x thickness of wall.
Thus, the total deduction =[(1 x h ) +((2/3)xlxr))]xthickness of wall where, I is the span of the arch/width of opening.'
Semi-circular Arch Openings
The area of semicircular portion = (1/2)llr2
The area of the semi-circular portion may also be obtained approximately by 314 x span x rise.
Thus, the total deduction =[(1 x h ) +((3/4)xlxr))] x thickness of wall Elliptical arches may be considered as semi-circular and may be dealt in same manner. For large arches, the actual area of opening shall be calculated correctly by mensuration formulae, and deducted.
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