what is plastering

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    In this post, I am going to explain what is plastering.

What is Plastering?

A Worker Applying Plaster 

     Plastering is actually a protective coating over the surface of Brick or Blockwork and over the surface of concrete or any other surface that needs to be protected it is prepared using cement and Sand / P-Sand in the Construction of Buildings in a specific ratio which we will see below.

What are the Uses of Plastering? 

    One of the uses of plastering is to provide a protective cover as I said before. Apart from that, plastering also provides a smooth finish to rough surfaces and helps us to prevent sharp edges of concrete by making them curved by using plastering otherwise it would be fatal if some people accidentally hit the structure. Plastering also helps us to create some architectural finishes like cornices in the external body structure etc.,. Another major advantage of plastering is that it can be used to produce the detailed finish that we want in walls that concrete can't able to achieve.

How many Coats of Plastering need to be done?

    We need to apply plastering based on the surface that we are going to cover. Since that base material may be even or undulated. Hence the number of coats of plastering may differ.

1. Brickwork or Hollow Clay tiles - 2 Coats or 1 Coat
2. Concrete, cast In Situ - 2 Coats or 1 Coat
3. Building Blocks / Blockwork - 2 Coats or 1 Coat
4. Wood or Metal Lath - 3 Coats or 2 Coats
5. Fibre building board ( Insulating Board) - 2 Coats or 1 Coat
6. Wood wool Slabs  - 2 Coat or 1 Coat
7. Cork Slabs - 2 Coats or 1 Coats
8. Uneven and Rough Stone Masonry - 3 Coats or 2 Coats

How much is the thickness of Plastering?

    Normally, the thickness should cover the undersurface in single-coat plastering to protect it. In the case of two-coat plastering, the plastering need not exceed 20mm thick for Walls and should not exceed 15mm thick for soffits ( Ceiling, under the waist of stairs, etc). In the case of three coats, the thickness should not exceed 25mm.

What is the Ratio for Plastering?

1. For single-coat plaster, the plastering in both Internal and External the Ratio of Cement: Sand needs to be either 1:3 1:4 or 1:6 and the thickness needs to be 10mm to 15mm.
2. For double-coat plaster, 
1. First coat / Backing Coat: The plastering in both Internal and External needs to be in the ratio of 1:3 1:4 or 1:6 and the thickness needs to be 10mm to 12mm.
2. Second coat / Finishing Coat - Cement: sand ratio needs to be  1:3 to 1:6 and the thickness needs to be 3mm to 8mm thick.
3. For Three Coat Plaster - Very Rough Surface - Both Internal and External
1. First coat / Backing Coat: The plastering in both Internal and External needs to be in the ratio of 1:3 1:4 or 1:6 and the thickness needs to be 10mm to 15mm.
2. Second coat - Cement: sand ratio needs to be  1:3 to 1:6 and the thickness needs to be 3mm to 8mm thick.
3. Finishing Coat - Fat Lime and Fine Dust or Marble Dust in equal proportions.

Which cement is best for Plastering?

Cement Bags

    There are two types of cement one is Called the OPC ( Ordinary Portland Cement ) and the other the PPC (Portland Pozzolana Cement). If you are very much interested in Cement check out the " What Cement is Made of " article written by me. 

    Among the two, PPC cement is best for plastering works. Compared to OPC, PPC has fly ash content in it which makes it a better workable mix at the same time it attains strength much higher than OPC in the longer Run. But if you prefer to go with OPC - OPC Has three grades such as 33, 43 and 53 Grades. For plastering go for 33 Grade OPC which is suitable for Plastering.

Which type of Sand is best for Plastering?

Sand

    You can use either river sand or P-Sand whichever you want but, the fineness modulus of the sand need not be less than 1.5. If you use sand below the fineness modulus the strength of the motor mix gets reduced. In the case of Double Plastering use sand with a Fineness modulus of not less than 2 for the base coat.

Method of Measurement of Plastering?

    Measurement of quantities and preparing the Bill of Quantities ( BOQ) is very important for our Cost forecast of the project which helps in the better planning and execution of Civil engineering works.

     Classification of Plastering

    

    Before a plastering measurement is taken, the plastering work needs to be classified according to the material used and each classification shall be measured separately. The below particulars need to be mentioned before each carrying out the measurement for each classified work.

1. Mix of Mortar
2. Number of Coats and thickness of each coat
3. Nature of Surface Treatment
4. Nature of base
5. Curved works, Conical Works, Spherical Work and Elliptical Work, Stating the radius
6. Any special treatment of base
7. The description shall include arises, Internal Rounded Angles, External Chamfers and/or rounded angles not exceeding 80mm in girth.
8. In the case of fibrous plaster, particulars of methods of application and treatment of joints shall be given
9. Repair works if any shall be described stating the thickness of dubbing

   Classification of Plastering Measurement based on Nature of Work

1. Plastering on roofs, Ceiling and Walls shall be measured separately
2. Removing plaster by scraping or otherwise shall be measured independently in square meters
3. Plastering of Isolated Widths such as bands, cornices, sunk, panels etc., and in chamfer and rounded angle, if the width or grith is 30cm or below it should be measured in Running meters and width/grith above 30 cm needs to be measured in square meters.
4. For Interior Plastering the Plastering need to be measured for Each floor.
5. For Exterior Plastering or any type of continuous plastering the height greater than 10m above ground/datum level shall be measured separately in stages of 5m height.

    Unit of Measurement of Plastering

1. All plastering shall be measured in Square meters or other dimensions if specifically mentioned.
2. If specifically mentioned, cutting to edges shall be measured in running meters or other dimensions.
3. Raking out of joints need be measured in sqm.
4. Raking out of single detached joint need to be measured separately in running meters.
5. Pointing in honey comb works needs to be measured in sqm.

    Deductions

1. No deduction shall be made for ends of joists, beams, posts etc. and openings not exceeding 0.5 sqm each and no addition shall be made for reveals, jambs, soffits, sills etc., of these openings nor for finish to plaster around ends of joists, beams, posts, etc.
2. Deductions openings exceeding 0.5 sqm but not exceeding 3 sqm each shall be made as follows and no addition shall be made for reveals, jambs, soffits, sills etc.,
1. When both sides of the wall of the opening are plastered with the same material. deduction needs to be made on only one side or half deduction need to be made on both sides.
2. When two faces of the wall are plastered with different types of plaster or if one face is plastered and the other pointed/plastered with other material, a deduction shall be made on the side where the depth of reveals is less and no deduction need to be made on the other side. In case the width of the reveal on both sides is equal then a 50% deduction needs to be made on both sides.
3. When only one face/Side is plastered and the other face is not, a full deduction needs to be made for the opening if the width of the reveal is less on the plastered side. In case the width of the reveal is more on the plastered side than on the non-plastered side then no deductions shall be made.
4. When the width of the door frame is equal to the thickness of the wall or is projecting beyond the thickness of wall, full deduction need to be made on both sides of the wall.
5. If one face is pointed and the other is not pointed, if the reveal width is less or no reveals on the pointed side then full deduction need be made on the pointing side. But if the width of the reveal is more than the non- pointing side, then no deduction need to be made and no any addition of reveals, jambs, soffits, sills need to be added extra.
3. For opening more that 3 sqm , full deduction need be made on both the side but jambs, soffits and sills shall be measured separately.

How much Material required for Plastering?

    Calculation of  material is very essential in construction for the planning and  purchasing of materials in advance for the works to move seamlessly. So the major materials used in the plastering were  Cement and Sand. How the materials need to be I already explained it in the top of the article. So I am going to give you the materials need for the 100 sqm of Plastering works along with the ratio and the plastering thickness that is commonly used in the construction industry for plaster finishes. The materials that I gave below are including of the wastage. If you reduce the wastage the material required will be much less. Wastage differ from place to place and the workmanship.

    For Inner Wall Plastering - For this, usually for single coat plastering is used, since most of the base materials used now a days were blocks or bricks or RCC wall which have a  less undulations if the workmanship of the block/ brickwork is good. Hence 12mm thick is used in construction industry. So, for walls we use 1:6 cement: sand ratio by employing this in 12mm thick plaster we need  8 bags of cement and 1.67 cum of P.Sand / Sand is required.  In Case if you are using 1:6 mortar  at 15 mm thick due to some unavoidable circumstances then you need 10 bags of cement and 2.12 cum of P.Sand / Sand is required for 100 sqm.

    For Ceiling Plastering  -  Ceiling plastering is done in 12mm thick since this will be of mostly concrete but the ratio employed mostly will be 1:4 cement : sand ratio because ceiling requires more binding properties than wall. In such a case you need 11 bags of cement and 1.55 cum of P.Sand / Sand required for 100 sqm.

    For External Wall Plastering - External Plastering are usually subject to extreme weather conditions hence a double plastering is usually employed. So the base coat will be of 1:6 mortar  at 12 mm thick and then a finishing coat of  1:6 mortar at 6 mm thick  so a total of 18mm thick  at 1:6 mortar is usually preferred , then you need  12 bags of cement and  2.5 cum of P.Sand / Sand is required for 100 sqm.

    

How Much labour required for Plastering?

A worker Plastering a Wall

    The below given labour will not include scaffolding/staging which need to be additionally added.

    For Inner Wall Plastering - To Complete 1 sqm of Wall Plastering of 12mm thick wall, including the mixing of mortar, Button mark fixing, Mesh and Box Packing works we need,

1. Mason - 0.064 Nos
2. MC - 0.08 Nos
3. FC - 0.08 Nos

    For Inner Wall Plastering - To Complete 1 sqm of Wall Plastering of 15mm thick wall, including the mixing of mortar, Button mark fixing, Mesh and Box Packing works we need,

1. Mason - 0.08 Nos
2. MC - 0.1 Nos
3. FC - 0.1 Nos

    For Ceiling  Plastering - To Complete 1 sqm of  Ceiling Plastering of 12mm thick wall, including the mixing of mortar, Button mark fixing, Mesh and Box Packing works we need,

1. Mason - 0.064 Nos
2. MC - 0.08 Nos
3. FC - 0.08 Nos

       For External Plastering - To Complete 1 sqm of Wall Plastering of 18mm thick wall, including the mixing of mortar, Button mark fixing, Mesh and Box Packing works we need,

1. Mason - 0.072 Nos
2. MC - 0.12 Nos
3. FC - 0.12 Nos

Rate Analysis of Plastering

    From the Data above we could be able to calculate the Rate in which the plastering work can be completed. The rates may vary depending on the location you are in and the availability of the material and labour. I am giving you the rate for 1 sqm of plastering works and its for the ground floor. If the plastering done on above floors then labour need to be added for shifting of materials.

    For Inner Wall Plastering (15 mm thick )- Material + Labour = INR. 80 + INR 216.5 = INR 296.5 ( For Project) or INR.326.5 ( For individual Resident)

    For Ceiling Plastering ( 12mm thick )- Material + Labour = INR. 63.25 + INR 173 = INR 236.25 ( For Project) or INR 260 ( For individual Resident)

    For External Plastering ( 18mm thick) - Material + Labour = INR.95 + INR 236 = INR 331 ( For Project) or INR 364.5 ( For individual Resident)

How many days of Curing is required for Plastering?

    The Curing of  Cement Plastered surface needs 6 to 7 days, Max 7 Days of Curing. But if special type of plasters other than cement plaster is required then it may required more days like even a month for curing.

Conclusion

    From the above I thick you will be clear with what is plastering and its requirement. Stay connected for more information with " www.thecivilengineer18.com". see you soon. 

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