Plaster work is a thin layer of cement mortar, applied over the masonry work. Plaster acts as a damp-proof coat over the masonry work. Plaster work also provides a finished surface over the masonry that is firm and smooth hence plaster enhance the appearance of the building. The primary objectives of plastering are to protect the surface from atmospheric influences, to cover the defective workmanship in masonry, to conceal porous materials and to provide a suitable surface for painting.
Courtesy - Pixabay
The material used for plaster must be tested as per specification. Sand should be tested for organic impurities, silt content, the particle size of sand, and bulking of sand. Sand from the river flowing through a plane area is not suitable for construction as it’s shall fall within the limits of grading zone IV.
- ASTM C926Standard Specification for Application of Portland Cement-Based Plaster
New Zealand Standards:
- NZS 4251-1 (2007): Solid plastering – Cement plasters for walls, ceilings and soffits [Licensed Building Practitioners Rules 2007, Building Code Compliance Documents B1 (AS1), B2 (AS1), E2 (AS1)
- BS EN 998-1 Specification for mortar for masonry – Part 1: Rendering and plastering mortar
Indian Standard (BIS codes):
- IS 383 Specification for coarse and fine aggregates for natural sources for concrete.
- IS 1542 Specifications for sand for plaster
- IS 2645 Specifications for integral cement water proofing compound
- IS 8112 Specification for 43 grade OPC
- IS 269 Specification for 33 grade OPC
- IS 1489 Specification for Portland Pozzolana cement
Most of the standard manuals have specified that the clay bricks should be of the first class, regular in shape, size and colour. It should have good crushing strength and absorb less water.
02. The Sequence of work:
Internal Brickwork must be completed before commencing the internal plaster work. In the case of external plaster work, you should have to finish the periphery brickwork of each floor first. The outside plaster work always start from the top of the building and finished at the bottom and ceiling plaster should be completed before commencement of wall plaster.
03. Quality Assurance for materials:
For the materials Field test and laboratory test Read: Precaution for Brickwork
04. Quantity Check and Stock Management OR Material Stock Management:
Plaster work is measured in area. The quantity of plaster works measured in the square meter of area. It is measured by multiplying length and height of the wall surface. The approximate materials used for 12 mm thickness in C: M 1:3 is 7.5 kg cement, and 0.015m3 sand is required per 1 m2 of plaster.The approximate materials used for 20 mm thickness in C: M 1:3 is 11.5 kg cement, and 0.024m3 sand is required per 1 m2 of plaster.
05. Tools and machinery:
For tools and machinery Read: Precaution for Brickwork
Proper steel/wooden scaffolding must be done for the interior wall plaster to meet specific site needs.In the case of the external periphery, it should be required to make double Steel scaffolding, sufficiently strong so as to withstand all loads likely to come upon it.It should be independent of work, and having two sets of vertical supports shall be provided.
07. Integration Of services:
Integration of services like HVAC, electric conduit, and plumbing line should be installed, and proper finishing must be done. Any Grooves, sleeves, and chases are shown in the drawing should be finished in right line, level, and position or as directed by the engineer. The sleeves of scaffolding should be finished properly and cured properly.
08. Workmanship for plaster work:
Courtesy - Pixabay
- Plasterwork must be started with adequate surface preparation. The joint of the brick wall should be racked out correctly. Dust and loose mortar should be removed by brushing and scrapping. The Surface should then be thoroughly washed with water, cleaned and kept wet before plastering is commenced.
- Sand should be screened through the sieve, and proportioning of cement mortar should be as per specification. Mortar should be used shortly after mixing, and excessive amounts of mortar should not be mixed at a time. It must be used within 30 minutes of adding water, if delayed either reject the mix or add adequate extra cement.
- 150 mm wide chicken mesh should be provided between the junction of column / beam and wall to prevent the cracks. Nails should be used 150 mm center to center for fixing chicken mesh.
- In the case of interior cement plaster with floating coat of neat cement, the quantity of cement applied for floating coat must be 1 Kg per Sqm.
- In the case of exterior plaster of 18 mm thickness, plaster must be done in two coats. The first layer of 12mm thick should be left rough and furrowed 2 mm deep with scratching tool and then apply 6 mm thick second layer.
- The plaster surface should be finished off true with a trowel and wooden float to give a smooth surface.
- The plasterwork should frequently be tested as the work proceeds with a true straight edge not less than 2.5 m long and with plumb bobs. Always check line, level and plumb of vertical or horizontal surface, edge
09. Testing of Work done:
- Proper surface preparation must be done before commencing the plasterwork.
- The materials used for plaster should be conformed to IS codes, and water cement ratio should be checked.
- Checking Level marks is necessary. Level Marks should be made with fresh mortar on all four walls. So that, after plastering room size is truly square or truly rectangular. Otherwise, when you fix floor tiles, you’ll face difficulties and ultimately it will look ugly.
- Plaster should be checked for the smooth surfaces and straight edges.
- Ensure that when chasing is done in brickwork for conduit pipes, the same should be filled with cement mortar and should be adequately cured.Holes made for scaffolding should also be filled correctly and cured sufficiently because holes are the major source of leakage or dampness in wall as curing at such location is always ignored.
10. Care After Work:
- Cleaning of doors or frame and floor area is necessary at the completion of work.
- Curing should be started as soon as the plaster has hardened sufficiently and must be cured for at least 7 days.
- Curing shall commence, 24 hours after the plaster is laid.
11. Safety Checks:
Courtesy - Pixabay
- Method statement for handling, placing and cleaning of materials must be prepared and must be followed.
- Personal protective equipment like safety helmet, safety belt, rubber hand gloves, goggles, facemask and rubber shoes should be ensured when handling work and First-Aid kit are immediately available on site.
- Proper ventilation and electric lights must be provided when plaster is carried out in a small space and a dark place.
- The material transporting machine should be checked for calibration frequently. Any error or defect that you see on the machine should be immediately repaired. Machine operator must have recognized agency’s license.
- Cleaning of area and housekeeping of material is necessary. Wastage of materials should be removed from the site as soon as possible.
12. Health Checks:
For health checks Read: Precaution for brickwork.
13. Wastage Management:
Wastage should be minimized by adopting proper construction methods. Waste management training program should be organized at regular interval on site. Waste materials should be stored safely and try to reuse or recycle.
Must Read: Types of Glass & Its Architectural Features!
14. Weather Checks:
For weather checks Read: Precaution for Brickwork.
15. Mode of measurement:
As per IS 1200 – 1976 (Method of measurement of building and civil engineering work P-XII, Plastering and pointing) dimensions shall be measured to the nearest 0.01 m areas shall be worked out to the nearest 0.01 m2. The length of plaster shall be taken between the brick walls or brick partitions (the dimensions before the plaster shall be taken), and for the height of plaster shall be taken from the top of the floor or skirting to the ceiling.
Deduction due to door/window/ventilation etc. follows the provision of IS Code: 1200 – 1976.