Lime plastering is one of those timeless crafts that bridges the gap between the ancient and the modern. It’s a process rooted in centuries of tradition, yet still the gold standard for restoring period properties and achieving natural, breathable finishes. From the first layer applied to the wall to the final trowel polish, the lime plastering process demands patience, precision, and an understanding of how natural materials behave over time.
This guide walks you through each step of the process, explaining not only how lime plaster is applied but why each stage matters. Whether you’re restoring a heritage property in Cambridge or building a sustainable new home, understanding the full lime plastering process helps you appreciate the craftsmanship that goes into every wall.
Step 1: Preparing the Surface
Before a single coat is applied, preparation is key. Lime plaster bonds best to porous, natural surfaces such as stone, brick, cob, or lath. The wall must be clean, stable, and free from dust, paint, or cement residues. Any modern gypsum or cement-based materials need to be removed, as they prevent the lime from breathing properly.
Once the substrate is clean, it’s often dampened with clean water. This stops the dry wall from sucking moisture too quickly out of the fresh plaster. In heritage buildings around Cambridge, where walls can be centuries old, this stage is especially important. A wall that’s too dry will cause the lime to crack prematurely; too wet, and it will slide or fail to adhere. Striking that perfect balance is part science, part instinct, and a skill that comes only with experience.
Step 2: The Base Coat (Scratch Coat)
The first layer, known as the base or scratch coat, provides the foundation for everything that follows. This coat is typically made with a coarse lime and sand mix, sometimes containing hair or fibre to add strength and prevent shrinkage.
It’s applied generously, often 10–12mm thick, and pressed firmly into the wall to ensure a strong bond. While still wet, the surface is lightly scored with a lath scratcher or comb. These shallow grooves create a textured key for the next coat to grip onto once dry.
At this stage, the plaster is not about beauty. It’s about stability. The goal is to create a solid, breathable foundation that can move naturally with the building. In older Cambridge homes, where walls subtly expand and contract with temperature and moisture, lime’s flexibility is one of its greatest assets.
The base coat is then left to dry slowly, sometimes several days or even a week, depending on the temperature and airflow. Rapid drying is avoided at all costs, as it can cause the lime to powder or craze.
Step 3: The Float Coat
Once the base coat has cured, the next layer, called the float coat, is applied. This coat is slightly finer, using a lime and sand mix with a smaller aggregate size. Its purpose is to level out the surface and provide a smooth, even background for the finishing coat.
The float coat is typically applied at around 6–8mm thick. After application, it’s ruled off with a straight edge to flatten the surface, then lightly compressed using a wooden float to consolidate the plaster. Timing again is crucial here. The plaster must be firm enough to resist trowel marks but still moist enough to be worked.
During this stage, lime plasterers often use a fine mist of water to keep the surface workable. The float coat may also be lightly keyed with a float covered in nails or a wire brush, giving just enough texture for the finish coat to adhere without slipping.
In a traditional Cambridge cottage or listed townhouse, the float coat can sometimes reveal the charming irregularities of old walls. Rather than trying to make them perfectly flat, skilled plasterers respect the building’s character, maintaining its subtle undulations and imperfections as part of its history.
Step 4: The Finish Coat
The final layer, the finishing coat, is where craftsmanship truly shines. This coat uses the finest lime putty and fine sand, sometimes mixed with marble dust for a silky, durable texture. Applied at around 2–3mm thick, it’s trowelled on in thin, even passes.
As it begins to firm up, the plasterer uses a steel trowel to smooth and compact the surface. Each pass compresses the lime, producing that characteristic soft sheen associated with traditional lime finishes. Depending on the desired result, the finish can be left matte and chalky or polished to a gentle lustre.
Some clients prefer a more rustic texture, while others want a refined, almost polished Venetian-style appearance. Lime’s versatility allows both, adapting to the aesthetic of the building and the homeowner’s preference.
Once completed, the finish coat must cure slowly, ideally protected from direct sunlight, wind, and frost. A light misting with water over the next few days helps control the drying process, ensuring even carbonation.
Step 5: The Carbonation Process
Unlike modern gypsum plaster, lime doesn’t set through chemical reaction but through carbonation, a natural process where lime absorbs carbon dioxide from the air and turns back into limestone.
This process is gradual and can take weeks or even months to fully complete. The result is a solid, breathable wall that continues to strengthen over time. The surface remains slightly porous, allowing moisture to evaporate naturally, which is one of the main reasons lime plaster is preferred for older and heritage properties.
Cambridge’s damp, temperate climate actually works in lime’s favour here. Moist air helps the plaster cure gently, producing a durable, long-lasting finish that can easily outlive the building itself.
Step 6: Finishing Touches and Decoration
Once fully carbonated, lime plaster can be left as-is or finished with breathable paints like limewash or clay-based emulsions. It’s crucial to avoid acrylic or vinyl paints, which seal the surface and trap moisture, undoing all the benefits of using lime in the first place.
Limewash, made from lime putty and natural pigments, complements the plaster beautifully. It enhances colour depth and texture while maintaining vapour permeability. Many Cambridge homeowners choose subtle earth tones or soft whites that highlight the natural character of the walls.
Why Lime Plastering Matters
Beyond aesthetics, lime plastering is about creating healthy, sustainable buildings. It regulates humidity, resists mould, and contributes to a comfortable indoor environment. Unlike modern plasters that trap moisture and can cause damp problems, lime lets walls breathe and works in harmony with traditional construction methods.
For those restoring period properties, lime is not a luxury. It’s a necessity. It protects original brickwork and stone while maintaining the authenticity that defines heritage homes. In new builds, lime plaster offers a sustainable, low-carbon alternative that complements modern eco-friendly materials.
The Craft Behind the Finish
Each stage of lime plastering, from the gritty base coat to the final polish, reflects centuries of craftsmanship passed down through generations. It’s a process that can’t be rushed or replicated by machines. The texture, tone, and warmth of lime plaster walls have a quality that modern materials simply can’t match.
For homeowners, architects, and conservationists in and around Cambridge, the value of traditional plastering goes far beyond the surface. It’s about preserving a connection to the region’s architectural heritage, the same spirit seen in the city’s colleges, churches, and cottages that have stood for hundreds of years.
And for those seeking expertise and authenticity in this craft, East Anglian Lime Plastering represents the continuation of that proud tradition, combining historic methods with modern precision to deliver results that endure for generations.
