Best Practices for DIY Interior Wall Plastering

Plastering interior walls can transform the look and feel of a room, giving it a smooth, professional finish. While traditionally considered a task for skilled tradespeople, DIY enthusiasts can achieve excellent results with the right materials, techniques, and preparation. This article explores the best practices for DIY interior wall plastering, guiding you step-by-step to ensure your plastering project looks polished and durable.

Understanding Interior Wall Plastering

Plastering involves applying a mixture of materials, commonly gypsum, lime, or cement-based compounds, to walls and ceilings. It serves both aesthetic and functional purposes: creating a smooth surface for painting or wallpapering, improving insulation, and sometimes offering soundproofing qualities.

Types of Plaster

• Gypsum Plaster: Made from calcium sulfate dihydrate, gypsum plaster is easy to work with and dries quickly. Ideal for interior walls and ceilings.
• Lime Plaster: Contains lime as the binding agent. It is breathable and flexible, often used in older buildings.
• Cement Plaster: A mix of cement, sand, and water. More durable but less breathable; typically used in areas exposed to moisture.

For most interior wall projects in homes, gypsum plaster is the preferred choice due to ease of use and smooth finish.

Tools and Materials Needed

Before starting your plastering project, gather all necessary tools and materials:

• Tools:
• Hawk (a flat square board for holding plaster)
• Steel trowel (for applying and smoothing plaster)
• Plastering float (for finishing)
• Mixing bucket
• Drill with mixing paddle attachment
• Sandpaper or sanding block (fine grit)
• Spirit level or straight edge
• Measuring tape
• Protective gloves and goggles

• Dust mask

• Materials:

• Ready-mixed gypsum plaster or plaster powder
• Clean water
• PVA bonding agent (optional but recommended)
• Primer or sealer (for substrate preparation)

Preparation: The Key to Success

Proper preparation is crucial to achieving a smooth, long-lasting finish. Skipping this step often leads to cracking, poor adhesion, or uneven surfaces.

Inspect and Repair Walls

Start by inspecting your walls thoroughly:

• Remove any loose paint, wallpaper residues, dust, or dirt.
• Repair cracks or holes using filler or patching compound.
• For new drywall installations, ensure joints have been taped and mudded properly.

Clean the Surface

Make sure the surface is clean and free of grease or dust. Wash down with mild detergent if necessary and allow the wall to dry completely.

Seal Porous Surfaces

Highly porous walls such as bare drywall or old brick absorb moisture quickly from plaster. Applying a PVA bonding agent diluted with water (typically one part PVA to four parts water) seals the surface and improves plaster adhesion.

Protect Surroundings

Cover floors and furniture with drop cloths or plastic sheeting to protect against spills. Mask window frames, sockets, and switches.

Mixing Plaster Correctly

Mixing plaster properly impacts workability and final appearance.

1. Read Manufacturer’s Instructions: Different brands may have varying water-to-plaster ratios.
2. Use Clean Water: Use cold clean water in a mixing bucket.
3. Add Powder Slowly: Gradually add plaster powder into the water while stirring continuously.
4. Mix Thoroughly: Use a drill mixer at low speed to blend until you have a smooth consistency without lumps.
5. Avoid Overmixing: Overmixing introduces air bubbles that create pinholes in the dried plaster.
6. Work Time: Note that gypsum plaster sets quickly, usually within 20-30 minutes, so only mix what you can apply within that window.

Application Techniques

Applying plaster requires patience and steady hands. Follow these steps for a professional finish:

First Coat (Scratch Coat)

The initial coat provides a base for subsequent layers:

• Using the hawk and trowel, scoop up some plaster.
• Apply it firmly onto the wall starting from the bottom upwards.
• Spread evenly with firm pressure aiming for about 3-6 mm thickness.
• Avoid putting on too much at once as it may sag.
• Keep edges neat as these will be blended later.
• Let this coat firm up slightly but not fully dry before applying the next layer (usually around 30 minutes).

Second Coat (Floating Coat)

This coat builds thickness and starts smoothing:

• Apply another 3-6 mm layer over the scratch coat once it has partially set.
• Use long sweeping motions with the trowel to level out imperfections.
• Push firmly but avoid gouging or scratching.
• Use a spirit level or straight edge intermittently to check flatness.
• Let this layer set until it is firm enough to support finishing.

Final Coat (Finishing Coat)

This thin coat provides the perfectly smooth surface:

• Mix the finishing plaster thinner than earlier coats for easier spreading (about 1-3 mm thickness).
• Apply carefully with gentle strokes using a clean trowel.
• Feather edges to blend seamlessly.
• As it begins to dry, use a wet sponge or brush lightly over the surface for a polished finish, this also helps close pores reducing sanding later.

Drying and Curing

Allow sufficient time for plaster to dry completely before painting or decorating:

• Drying depends on temperature, humidity, and thickness; expect several days for full curing.
• Avoid rapid drying by keeping windows closed if weather is hot or dry; slow drying reduces cracking risk.

Sanding and Finishing Touches

Once fully dry:

• Lightly sand any rough spots using fine-grit sandpaper.
• Wear a dust mask during sanding to avoid inhaling dust.
• Remove dust using a soft brush or vacuum before applying primer or paint.

Common Mistakes to Avoid

To ensure success, steer clear of these pitfalls:

• Applying too thick coats resulting in sagging or cracking.
• Mixing too large batches causing plaster waste due to rapid setting.
• Skipping surface preparation leading to poor adhesion.
• Not sealing porous surfaces causing uneven drying.
• Rushing drying time leading to shrinkage cracks.

Tips for Best Results

• Work in small sections manageable within your pot life of mixed plaster.
• Maintain consistent pressure on your trowel for even application.
• Keep tools clean during work, dried material affects smoothness.
• Consider practicing on a small wall area first if new to plastering.

When to Call in Professionals

While DIY plastering can be rewarding, some situations require expert intervention:

• Large-scale cracks caused by structural issues
• Walls with moisture problems like dampness
• Decorative plaster finishes such as Venetian stucco

In these cases professional assessment prevents wasted effort and expense.

Interior wall plastering done well enhances home interiors dramatically while providing a great sense of accomplishment from doing it yourself. By following these best practices, from careful preparation through mixing right and applying skillfully, you can achieve smooth walls worthy of any professional painter’s canvas. Take your time, pay attention to detail, and enjoy the transformation your newly plastered walls bring!