Interior Plastering Process: Preparation, Application and Finishing

 

Interior Plastering Process: Preparation, Application and Finishing |Thickness of internal plaster | Internal plaster ratio | Internal plaster proportion

Interior Plastering: Preparation and Process

Plastering is an essential finishing activity in building construction that enhances the smoothness and aesthetic appeal of walls and ceilings. Proper interior plastering not only makes the structure look beautiful but also provides protection from external weather conditions, preventing moisture penetration. Let’s dive into the detailed steps involved in the preparation and process of interior plastering.

 

Step-by-Step Guide for Interior Plastering

1. Surface Preparation

Proper surface preparation is crucial to achieve a durable and high-quality plaster finish.

 

Surface Cleaning: Start by cleaning the surface thoroughly. Remove all loose material, dust, grease, oil, and mortar splashes. If the surface has been previously painted or has remnants of previous plaster, they should be scraped off.

 

Surface Wetting: For brick or block walls, wet the surface evenly to prevent excessive absorption of water by the plaster. This ensures better adhesion and reduces the chances of cracks forming due to rapid drying.

2. Applying the chicken mesh

This is the most important step when dealing with beam and masonry joints.

Cut the chicken mesh: Cut the mesh into strips, wide enough to cover both the concrete beam and the surrounding brick/block masonry. The width should typically extend 100-150mm on either side of the joint.

 

Fix the mesh: Place the chicken mesh over the joint, ensuring it overlaps both the beam and the masonry evenly. Secure the mesh using nails or wire ties at approximately 300mm intervals to keep it level with the surface. Ensure the mesh does not protrude or leave any gaps between it and the wall.

 

Applying key coat (bonding coat): In case of concrete surfaces, apply a bonding agent or key coat (made of cement slurry mixed with adhesive) to improve the adhesion of the plaster.

 

Fixing electrical fittings: Ensure that electrical conduits, junction boxes and other fixtures are properly installed and secured in their respective positions before starting the plastering process.

 

3. Choosing the plaster mix

The mix ratio depends on the nature of the surface and the strength required. Common mix ratios include:

 

Cement-sand ratio: A common mix for interior plastering is 1:4 or 1:6, where 1 part cement is mixed with 4 to 6 parts sand. The choice depends on the type of surface and the desired finish.

 

Use of additives: To improve workability, strength or crack resistance, additives such as waterproofing compounds or plasticizers can be mixed into the plaster.

 

Sieve the sand: Make sure the sand used for plastering is fine and does not contain any impurities. It must be sieved to avoid any lumps that may affect the finish of the plaster.

 

4. Plastering Process

Once the surface is prepared and the mixture is ready, follow these steps to apply the plaster:

 

Step 1: Applying the first coat (scratch coat)

Thickness: The first coat of plaster is generally 12-15 mm thick.

 

Application: Apply the plaster using a trowel or mason's tool starting from the top of the wall and moving downwards. Spread it evenly over the surface ensuring a uniform thickness.

 

Scoring: Once the first coat is applied, allow it to set a little. Before it hardens completely, score the surface with a trowel or comb tool to create a rough texture. This keying helps the second coat stick better.

 

Step 2: Applying the second coat (finishing coat)

Thickness: The second coat, or finishing coat, is typically 6-8mm thick.

 

Application: After the first coat has cured, apply the finishing coat. The second coat should be thinner and applied more carefully to ensure a smooth, flat finish. Use a steel float to spread the mixture evenly and smooth out any imperfections.

 

Smoothing and levelling: After applying the plaster, smooth and level it using a wooden float or steel trowel. Make sure that the corners, edges and junctions of walls and ceilings are properly aligned and smooth.

 

5. Curing the plaster

Proper curing is very important for the strength and durability of the plaster. Start curing 24 hours after applying the finishing coat.

 

Curing period: It should take at least 7 days to cure, with the plaster being sprayed with water at regular intervals. Make sure that moisture is maintained to prevent the surface from drying out prematurely, which can lead to cracks.

 

6. Final inspection and touch-up

 

Once cured, inspect the plastered surfaces for any imperfections, such as cracks, uneven texture or rough patches. Minor problems can be fixed with touch-up plaster, while major problems may require re-plastering of some areas.

 

Final finishing: For a perfectly smooth finish, some people may prefer to apply a final coat of POP (plaster of Paris) or similar fine material over the plaster.

 

Key points to remember:

Quality of materials: Always ensure that the cement, sand and additives are of high quality for a long-lasting finish.

 

Consistency of the mix: The plaster mix should be of the right consistency – not too dry, which can lead to cracks, or not too wet, which can lead to loosening.

 

Environmental considerations: Avoid plastering in extremely hot or windy conditions, as rapid drying can cause cracking.

 

Conclusion

Interior plastering, when done correctly, transforms the bare walls of a structure into a smooth, finished surface ready for painting or decorating. By following proper preparation and application techniques, you can achieve a durable and visually pleasing result. Whether you are a contractor, engineer or homeowner, understanding the nuances of interior plastering ensures the best results for your project.