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Plastering internal corners is one of those things you notice straight away when it’s not done properly. It might look like just another step in finishing a wall, but it actually takes a bit more care. You need a steady hand, good timing, and a clear understanding of layering.
When done properly, internal corner plastering creates a seamless transition between two walls, giving the entire room a clean appearance. When done poorly, the result is visible lines or cracking that becomes more obvious over time.
In this blog, we’ll go through how to plaster corners step by step. You’ll learn what to use and how to apply it properly.
Each tool serves a specific purpose, and skipping or substituting them leads to inconsistent results.
Tools
Materials
Before applying any compound, the plasterboard should be checked to ensure it is securely fixed in place. Screws should be slightly recessed without breaking the surface of the board, and the edges of the sheets should align evenly along the corner.
The area should also be free from dust, debris, and loose material that could interfere with adhesion. Cleaning the corner seems like a small task, but it improves how the compound bonds to the surface.
The compound should be mixed to a smooth and workable consistency before application. It needs to be thick enough to stay on the knife without dripping, yet soft enough to spread easily across the surface.
If the mixture is too thick, it will drag and leave ridges. If it is too thin, it will not hold its shape in the corner. Achieving the right balance allows for controlled application and a cleaner finish.
The first coat forms the base layer for the internal corner. Using a joint knife, apply compound evenly. This layer does not need to be perfectly smooth. Its main purpose is to provide enough material to embed the tape securely. Consistency is more important than appearance at this stage.
Paper tape is essential for reinforcing internal corners and preventing cracks.
Starting at the top of the corner, press the tape into position and work downwards, ensuring it remains centred. A joint knife should then be used to press the tape firmly into the compound while removing excess material.
This step requires careful pressure to avoid trapping air bubbles or displacing the tape. Proper embedding ensures the corner remains stable over time.
After the tape has been embedded, the surface should be lightly smoothed using a joint knife.
The compound should then be left to dry completely before applying additional coats. Drying times can vary depending on environmental conditions, but allowing at least 12 to 24 hours is recommended.
The second coat defines the shape of the corner and improves the overall surface. The compound should be applied over the taped area, extending slightly wider than the first coat.
The edges should be feathered carefully so that the compound blends into the surrounding wall. This stage requires attention to detail, as it sets the foundation for the final appearance.
The final coat focuses on achieving a uniform finish. A topping compound is used for this stage, because it is easier to spread and sand.
The compound should be applied in a thin layer, extending further out from the corner to eliminate any visible transitions. Light and even pressure should be used to create a consistent surface.
By this stage, the corner should already appear clean and well-shaped before sanding begins.
Once the final coat has dried, the surface should be sanded lightly using fine-grit sandpaper. The aim is to remove minor imperfections and create a smooth finish suitable for painting.
Over-sanding should be avoided, as it can expose the tape and damage the surface. Checking the corner under good lighting helps identify any remaining inconsistencies that need attention.
Plastering internal corners properly requires a combination of preparation, technique, and patience. Each stage of the process plays a role in the outcome, and rushing through any part leads to visible defects.
By focusing on consistent application, proper reinforcement, and careful finishing, it is possible to achieve professional results that hold up over time. Internal corners are a small part of the overall wall, but their impact on the final appearance is significant.
If you’d rather leave it to experienced hands or want a guaranteed quality finish, Sydney Wide Plastering is available to help with your project. Our team handles everything from small repairs to full-scale plastering projects.
Call us today on 0405 847 224 to speak with our plasterers in Sydney, or submit a quick enquiry through our online form to request a quote.
