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Monday, 8 January 2018

PLASTERING

Cement plastering is commonly used as ideal coating for external and internal surface of wall. Cement plaster is usually applied in a single coat or double coat. Double coat plaster is applied where thickness of plaster is required to be more than 15 mm or when it is required to get a very fine finish. The process of applying a double coat cement plaster on wall surface consists of the following steps.
§  Step 1-Preparation of surface for plastering
§  Step 2-Ground work for plaster
§  Step 3-Applying first coat (or under coat or rendering coat)
§  Step 4-Applying second coat (or finishing or fine coat)

STEP-1 (PREPARATION OF SURFACE FOR PLASTERING)
1.     Keep all the mortar joints of wall rough, so s to give a good bonding to hole plaster.
2.     Clean all the joints and surface of the wall with a wire brush, there should be no oil or grease etc. left on wall surface.
3.     If the surface is smooth or the wall to be plastered is old one, then rake out the mortar joint to a depth of at least 12mm to give a better bonding to the plaster.
4.     If the projection on the wall surface is more than 12mm then knock it off, so as to obtain a uniform surface of wall. This will reduce the consumption of plaster.
5.     If there exist any cavities or holes on the surface, then fill its in advance with appropriate material.
6.     Roughness the entire wall to be plastered.
7.             Wash the mortar joints and entire wall to be plastered, and keep it wet for at least 6v hours before applying cement plaster.

STEP-2(GROUND WORK FOR PLASTER)
1. In order to get uniform thickness of plastering throughout the wall surface, first fix dots on the wall. A dot means patch of plaster of size 15mm*15mm and having thickness of about 10mm.
                  2. Dots are fixed on the wall first horizontally and then vertical at a                                                         distance of about 2 meters         
3. Check the vertically of dots, one over the other, by means of plumb-bob.
4.            After fixing dots, the vertical strips of plaster, known as screeds, are formed in between the dots. These screeds serve as the gauges for maintaining even thickness of plastering being applied.

STEP-3(APPLYING FIRST COAT OR UNDER COAT OR RENDERING COAT)
1.     In case of brick masonry the thickness of first coat plaster is in general 12mm and in case of concrete masonry this thickness varies from 9 to 15 mm.
2.     The ratio of cement and sand for first coat plaster varies from 1:3 to 1:6.
3.     Apply the first coat of plaster between the spaces formed by the screeds on the wall surface. This is done by means of trowel.
4.     Level the surface by means of flat wooden floats and wooden straight edges.
5.     After levelling, left the first coat to set but not to dry and then roughen it with a scratching tool to form a key to the second coat of plaster.


STEP-4(APPLYING SECOND COAT OR FINISHING COAT OR FINE COAT)
1.     The thickness of second coat or finishing coat may vary between 2 to 3 mm.
2.     The ratio of cement and sand for second coat plaster varies from 1:4 to 1:6.
3.     Before applying the second coat, damp the first coat evenly.
4.     Apply the finishing coat with wooden floats to a true even surface and using a steel trowel, give it a finishing touch.
5.     As far as possible, the finishing coat should be applied starting from top towards bottom and completed in one operation to eliminate joining marks.



After completion of plastering work, it is kept wet by sprinkling water for at least 7 days in order to develop strength and hardness.


FIRE FIGTHING SYSTEM
SR.NO
DESCRIPTION
AS PER NBC 2005
PART
DESIGN AS PER APOSTLE
1
Type of building
Residential building
Type:A-4 apartment

2
Height of building
Above 60m

3
Fire Extinguishers
Required
Provided
4
Hose reel
Required
Provided
5
Dry Riser
Not required
Not provided
6
Wet Riser
Required
Provided
7
Down corner
Not required
Provided
8
Yard Hydrant
Required
Provided
9
Automatic sprinkler system
Required
Provided in common areas and basements
10
Manually operated electrical  alarm system
Required
N/A, as automatic detection system is proposed
11
Automatic detection alarm system
Required
Provided as per NBC
12
Under ground water storage(static)tank
100,000
Provided 200000 litres

13
Terrace tank
25,000
Provided on each block
14
Pump capacity near underground static water storage tank (fire pump) with minimum pressure of 3.5 kg/sq.cm at terrace level
1.Two electrical pumps 2850LPM
2.One diesel pump 2850LPM
3.Two electrical jockey pumps -180LPM

1. Provided 2nos multistage, multi outlet main fire pumps for hydrants and sprinkler system.
2. Provided
3. 2nos electrical jockey pump provided, one for lower zone and other for upper zone.

15
Pump capacity at the terrace tank level within minimum pressure of 2.0 kg/sq.cm
Not required
Provided 1no fire pump.

Considering number of hydrants and risers for towers, pump capacity to be designed and selected as per norms.



Fire fighting system has been designed as per NBC and by local Bylaws. If any areas is not covered by NBC, it shall be designed as per NFPA and local codes.


Fire Hydrant system shall cover the internal & external hydrants connected to the common fire fighting through main hydrant lines. It is proposed to providing automatic sprinkler system for basement & all upper floors.

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