Cement plaster is used for both internal and external surfaces on the wall. Plastering is usually done on the walls to achieve a smooth surface and remove any undulations or irregularities on the wall before plastering. Cement plaster is prepared by mixing portland cement, sand and water.
Guidelines for Cement Plastering
1. Surface Preparation and Ground Work
- Ensure that the Beam and Brick work joints are filled with non-shrink mortar minimum a day before the application of Chicken mesh on the plastering surface
- Ensure that all chasing (for electrical and plumbing lines) in the wall are properly filled with atleast 10mm recess and with chicken mesh
- Chicken mesh should be fixed firmly at the joint of brickwork and RCC (coloumns and Beams). Also ensure that there is an overlap of at least 100 mm on both sides
- The surface recieving plaster should be cleaned properly. All the loose material should be removed like loose mortar, if fungus is present on wall it should be scraped and cleaned with wire brush. The surface should be free from any defect like dirt, dust, oil, curing compound, grease, wooden pieces, foam sheet, or any unwanted material
- Provide inserts, opening, groves, recesses as per drawing
- Check for the line and plumb of button marks should be checked
- Any defect in RCC (Bulging or Honeycomb) should be rectified before plastering. Read in detail on How to rectify Honeycomb defects in concrete
- Check for marking for Architectural features if any (Refer construction drawings)
- Don’t make any holes in the wall for scaffolding
- If the projection on the wall surface is more than 12 mm, then knock it off, so as to obtain a uniform surface of wall. This will reduce the consumption of plaster.
- Check for availability of correct size measuring box and mixing tray. Measuring box is used to proportiante cement and sand required for plastering work. Also arrange for water required
- Arrangement for collection of rebound material & recycle it within 45 mins to avoid wastages
- Ensure the following tools and tackles are available before start of plastering
2. Steps to be followed during plastering
- Start the plaster with application of cement slurry added with bonding agent (Latex – 5% by weight). The mortar application on RCC member should start 15 mins after cement slurry application but not later than 60 mins.
- Ensure that the mortar is batched, mixed properly
- Ensure that the material is consumed in 1 hour after mixing water
- Ensure uniform finishing as per site instruction and drawing.
- Ensure the simultaneous removal of embedded supports.
- Avoid holes in walls.
- Check for line, level, dimensions, diagonal, plumb of the plastered surface
- Check the line, level, size, and correctness of location of groves and other architectural features.
- If plaster is done in two coats ensure the gap of at least three days and not more than 7 days. If gap is more than 7 days use bonding agent. (2nd coat < 8 mm)
- Separate Mason to be deployed for finishing of opening to make sure the slope, plumb dimensions of opening are as per drawing
3. Steps to be followed Post Plastering
- The date of plaster has to be mentioned on the wall
- Ensure that water curing is done for at least 7 days before application of painting. This will help the cement plaster develop strength and reduce cracks due to heat of hydration.