At a glance
Plastering is one of the most satisfying DIY skills to acquire and one of the most in-demand. A competent plasterer can charge upwards of £200 per day in most parts of the UK, and even a small patch repair to a wall or ceiling can cost significantly more than the materials involved. Learning to plaster – even to a good amateur standard rather than a professional finish – saves real money on every renovation project and gives you a skill that gets steadily better with practice.
The honest caveat is that plastering is not a beginner skill in the way that painting or tiling is. Getting a flat, smooth finish requires understanding how the material behaves as it sets, developing a consistent trowel technique, and managing the working time before the plaster hardens. The first attempt almost always disappoints. The second is noticeably better. By the third or fourth wall most people are producing a finish that needs only minor sanding before decorating. This guide covers the full process for a two-coat system on a brick or block wall, plus the slightly different approach for patch repairs.
What you’ll need
Types of plaster
Choosing the right plaster for the job is the first decision to get right, and it depends on what surface you are plastering onto and what finish you want to achieve.
For a bare brick or block wall – the most common scenario in a renovation – the correct system is bonding coat followed by finishing plaster. The bonding coat is applied thickly (8-11mm), scratched to provide a key while still soft, and left to harden fully before the finishing coat is applied. The finishing coat goes on at 2-3mm and is worked to a smooth, flat surface. This two-coat system gives the most reliable result on difficult substrates. For a wall that has had old plaster removed and is being replastered onto exposed plasterboard, board finish alone is applied directly to the board surface as a thin skim.
Preparing the wall
Wall preparation determines the quality of the finished plaster as much as technique does. Skipping or rushing the preparation phase is the most common reason plaster fails – either by not bonding properly, developing cracks, or blowing away from the wall within months of application.
Start by removing all loose or blown plaster. Tap the existing surface with a knuckle and listen for a hollow sound – hollow areas have lost their bond with the substrate and must be removed entirely before replastering. Use a bolster chisel and club hammer to cut back to a sound edge, undercutting slightly to give the new plaster something to grip. Clean all dust and debris from the wall surface with a stiff brush. Any mould must be treated with a fungicidal solution and allowed to dry fully before plastering proceeds – never plaster over active damp or mould as it will reappear through the finish coat.
Once the surface is clean and sound, apply a diluted PVA solution – one part PVA to five parts water – with a brush or roller, covering the entire area to be plastered. Allow this first coat to dry, then apply a second coat of stronger PVA (one part to three parts water) and plaster while this second coat is still tacky. The tacky PVA dramatically improves adhesion and regulates the suction of porous brick and block, which would otherwise draw moisture out of the plaster too quickly and cause it to crack before it can be worked.
How to plaster – step by step
Mix the bonding coat
Add clean water to the bucket first, then add bonding plaster gradually while mixing – not the other way round. Mix to a thick, smooth consistency with no dry lumps. The mix should hold its shape on the hawk but spread easily from the trowel. Mix only what you can apply in 30-40 minutes.
Apply the bonding coat
Load the hawk and transfer plaster to the trowel. Apply with firm, sweeping strokes, working from the bottom of the wall upward and pressing the plaster firmly into the surface. Aim for an 8-11mm thickness. Work in sections and maintain a wet edge to avoid visible joins. Use a straight edge or feather edge to level the surface as you go.
Scratch the bonding coat
Before the bonding coat fully sets – when it has firmed up but can still be marked – scratch the surface with a deviling float or a piece of wire mesh dragged across it. These scratches provide a mechanical key for the finishing coat to grip. Leave the bonding coat to harden fully – typically 24 hours minimum, longer in cold or humid conditions.
Apply the finishing coat
Dampen the bonding coat lightly with a water spray before applying the finish. Mix finishing plaster to a smooth, creamy consistency – thinner than bonding. Apply at 2-3mm in two thin passes: first to cover the surface completely, second to flatten and begin smoothing. Work quickly – finishing plaster has a shorter working window than bonding coat.
Flatten and polish the finish
As the finishing coat begins to firm – when it has lost its shine but is not yet hard – work over the surface with long, firm, overlapping trowel strokes to flatten any ridges. Lightly mist the surface with water if it is drying too fast. As it hardens further, use increasingly light, polishing strokes with the trowel held at a low angle to the wall to bring up a smooth, tight finish.
Allow to dry fully before decorating
Fresh plaster must dry completely before painting or papering – typically 4-6 weeks for a full two-coat system in a well-ventilated room. New plaster appears dark pink-grey when wet and lightens to a uniform pale buff colour when fully dry. Applying paint or wallpaper to incompletely dried plaster traps moisture and causes adhesion failure. Mist coat the dry plaster with heavily diluted emulsion before full decoration.
Work from the bottom up on the bonding coat, top down on the finishing coat. Applying bonding from the bottom prevents the heavy material from sagging and dragging down over freshly applied sections below. Finishing, being much thinner, benefits from working top to bottom so that any material that drops falls onto unfinished wall rather than the polished surface you have just completed.
Patch repairs
Patch plastering – filling a hole or damaged section in an existing wall – follows the same principles as full plastering but requires additional care at the edges where new plaster meets old. The biggest visual problem with patch repairs is a visible outline where the patch meets the surrounding wall, either because the new plaster sits proud of the old or because the texture does not match exactly. Cutting back the damaged area to a clean, square edge rather than leaving a ragged perimeter gives a cleaner, less visible join.
For small holes up to 15-20cm across, one-coat filler or one-coat plaster applied in layers is the most practical approach – these products are formulated to work without the two-coat bonding system and are more forgiving in small applications. For larger areas, the full bonding coat plus finishing coat process applies. Dampen the edges of the existing plaster and the exposed substrate before applying the bonding coat, and feather the finishing coat out onto the surrounding existing plaster surface by a few centimetres to disguise the transition.
Common problems and solutions
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