Plastering an existing plaster wall, often referred to as skimming, involves applying a thin layer of new plaster to create a smooth, even surface. The process typically follows a series of steps, starting with preparation and ending with finishing touches.
The Process of Plastering a Plaster Wall
Based on standard techniques and the provided reference steps, here is a guide to plastering a plaster wall:
1. Step 1 - Preparation
Before applying any new plaster, thorough preparation is crucial. This involves cleaning the wall surface to remove any dirt, dust, or loose debris. Any existing damage, such as cracks or holes, should ideally be repaired beforehand. A clean, stable surface ensures proper adhesion of the new plaster layer.
- Clean the wall thoroughly.
- Address any existing imperfections or damage.
2. Step 2 - Apply PVA to Walls
Applying a coat of PVA (Polyvinyl Acetate), often diluted, is a critical step. PVA acts as a bonding agent, sealing the porous surface of the existing plaster and providing a key for the new plaster to adhere to. Apply it evenly and allow it to become tacky before proceeding. Multiple coats may be necessary on very porous surfaces.
- Apply a diluted PVA solution to the entire wall surface.
- Allow the PVA to become tacky (partially dry).
3. Step 3 - Mix Plaster
Mixing the plaster correctly is vital for a smooth finish. Plaster powder is typically mixed with clean water in a plasterers' bucket. Add the powder to the water gradually while mixing until a smooth, lump-free consistency is achieved. The mix should be workable – not too stiff, not too runny.
- Add plaster powder to water in a clean bucket.
- Mix thoroughly until smooth and lump-free.
4. Step 4 - Apply Plaster
Using a hawk and trowel, begin applying the mixed plaster to the wall. Start from a corner or edge and work in sections. Spread the plaster evenly over the surface, aiming for a consistent thickness, typically a few millimeters.
- Load plaster onto a hawk or trowel.
- Spread the plaster onto the wall using a trowel.
5. Step 5 - Skimming and Smoothing
Once the plaster has been applied, the next phase involves skimming and smoothing the surface. Use a clean trowel to flatten and smooth the applied plaster, removing any trowel marks and filling in low spots. This is done while the plaster is still wet but beginning to firm up slightly.
- Use a trowel to flatten and smooth the wet plaster.
- Remove trowel marks and achieve an even surface.
6. Step 6 - Scrape
As the plaster starts to firm up further, scraping may be required, particularly after the first coat or if any high spots are present. Using the edge of a trowel held at a slight angle, gently scrape back any ridges or uneven areas. This helps prepare the surface for subsequent layers or final finishing.
- Gently scrape back any high spots or ridges with a trowel.
7. Step 7 - Add Another Coat of Plaster
Often, a single coat isn't sufficient to achieve a perfectly smooth finish. A second coat of plaster is typically applied over the first one after it has firmed up adequately but is not yet fully dry. The second coat is applied in the same manner as the first, focusing on achieving a perfectly flat and smooth surface.
- Apply a second thin coat of plaster over the first, partially set layer.
8. Step 8 - Finishing Touches
The final step involves achieving the ultimate smooth finish. This is done through further smoothing and "polishing" with a clean trowel as the second coat of plaster continues to dry and firm up. Techniques like "trowelling up" involve pressing the trowel firmly against the surface and gliding it over the plaster to bring moisture to the surface and create a highly polished, glass-like finish.
- Smooth and polish the final layer with a clean trowel.
- Continue working the surface until the desired smoothness is achieved.
Following these steps helps ensure a professional-looking, smooth finish when plastering over an existing plaster wall.
