Quantities of Cement and Sand in Plaster

CALCULATE QUANTITIES OF CEMENT AND SAND

REQUIRED FOR MORTAR

Mortar is a workable paste which dries to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, and sometimes to add decorative colors or patterns to masonry walls. In its broadest sense, mortar includes pitch, asphalt, and soft mud or clay, as used between mud bricks

                                                

Quantities of materials in cement mortar is required for carrying out rate analysis for RR Masonry walls, brickwork and plastering works.

Cement mortar can be specified in various proportions like 1:1, 1:2, 1:3, 1:4, 1:6, 1:8 etc.

1:1 represents 1 part of cement and 1 part of sand

1:2 represents 1 part of cement and 2 parts of sand and so on..,

Cement Mortar for Plastering:

(100 Sqm and 12mm Thick)

The calculation of cement & sand in 1:6 shall be calculated as follows

Let us assume a 12mm thick plaster and a mix ratio of 1:6.

We are calculating for 100 Sqm and 12 mm thickness (Assumption).

Plastering thickness 12 mm = 12/1000 = 0.012m

Volume of cement mortar required = ( Plastering Area x thickness )

= 100 m² x 0.012m = 1.2 m³

(This is wet volume that means we need this much volume of cement mortar after mixing water, So for dry volume, we have to add 30-35% as bulkage of sand, we are using 35% and wastage as 20%)

Consider 35% Sand Bulkage & 20% Wastage

= 1.2 m³ x (1+0.2+0.35)

(Many of us would use 1.54 as constant)

= 1.86 m³

Cement : Sand (Ratio) = 1 : 6 ( Total = 1+6 = 7 Parts )

Cement required (1 Part) = 1.86 x 1/7

= 0.265 m³ /0.0347

= 7.66 bags (Approx – 8 Bags)

Sand required (6 Part) = 1.86 x 6/7

= 1.53 m³

Cement Mortar for 1m³:

Calculate the dry volume of materials required for 1m³

Consider 35% Sand Bulkage & 20% Wastage

= 1.0 m³ x (1+0.2+0.35)

= 1.55 m³

Cement : Sand (Ratio) = 1 : 6 ( Total = 1+6 = 7 Parts )

Cement required (1 Part) = 1.55 x 1/7

= 0.22 m³ /0.0347

= 6.368 bags

Sand required (6 Part) = 1.55 x 6/7

= 1.328 m³

Some Quick Tips:

If the mortar is weak: Not only will the mortar fail to bind sufficiently, it may also crumble after a short amount of time or wash away after minimal weathering.

If the mortar is strong: Too strong a mix, i.e made with too much cement and your mortar may dry too quickly, shrink and crack. 

Cracking can be avoided by reducing the amount of cement in the mixture and ensuring the mortar is wet enough.

Before beginning to work on the plastering calculation, note down these general things

Cement Mortar Ratio for wall plastering 1:6

Cement Mortar Ratio for ceiling plastering 1:4

Plastering thickness generally adopted for interior walls is 12mm and for exterior walls it is 20mm.

Always use good quality of cement & Sand. Sand should always be from silt

Always measure the quantities using a measuring box (not head pan) for site mix.

A bag of mortar should be mixed with correct quantity of clean water to achieve the right consistency.

The amount of water used can vary drastically depending upon the weather, how wet the sand is, and the variety of mix you're using.

Ambient conditions (temperature and humidity) will affect the mix and need to be considered.

Plastered walls shall be level to the plumb

Reference can be made to IS 2250 (1981): Code of Practice for Preparation and Use of Masonry Mortars [CED 13: Building Construction Practices including Painting, Varnishing and Allied Finishing]