- 1. Overview
- 2. Composition and Material Science
- 3. Layer System — Generic Application Sequence
- EN 459–1 NORM : “Construction Limes – "Specifications and conformity criteria" 1/9/2002
- 4. Key Physical and Environmental Properties
- 5. Mechanism of Breathability and Salt Resistance
- 6. Role in Heritage and Restoration
- 7. Testing and Quality Standards
- 8. Practical QA / Site Checklist
- 9. Sustainability Insights
- 10. Specification Template (Generic)
- 11. Key Takeaway
1. Overview
Lime plaster is a traditional yet scientifically relevant building material used for sustainable architecture and heritage conservation. It is composed primarily of natural hydraulic lime (NHL), aggregates, and pozzolans, and it hardens through hydration and carbonation, forming a breathable and flexible matrix. Lime plaster systems allow masonry to breathe, control rising damp, manage salts, and preserve the mechanical and aesthetic integrity of walls for decades.
Cement Walls
Advantages
- Thin and light structures.
- High strength and load capacity.
- Great works realization
Disadvantages
- Condensations and mould.
- High thermal conductivity
- Poor walls breathability
- Rigid structures
Improper use of cement
- Cement-based plasters, renders and finishing.
- Use in construction mortars
μ = Vapour transpiration. It indicates the resistance of a solid towards vapour permeability.
λ = Thermal conductivity. It indicates the capacity of a solid to conduct and scatter heat
2. Composition and Material Science
Component | Function | Notes / Standards |
Natural Hydraulic Lime (NHL 2–3.5) | Primary binder — hardens through hydration and carbonation | Defined under EN 459-1 |
Pozzolanic Additives | React with lime to enhance hydraulic strength and sulfate resistance | Volcanic ash, natural pozzolans, calcined clays |
Aggregates (Dolomitic / Siliceous Sands) | Control shrinkage, improve porosity and mechanical stability | Rounded river sands preferred |
Marble Dust / Inert Fillers | Improves smoothness and finish | Common in finishing coats |
Natural Organic Modifiers | Enhance workability and flexibility | Casein, cellulose, starch, plant resins |
Pigments (Earth Oxides) | Colouration | UV-stable, natural mineral pigments |
3. Layer System — Generic Application Sequence
Stage | Purpose / Function | Typical Thickness |
1. Surface Preparation | Remove cement renders, efflorescence, open pores | — |
2. Cleaning | Hydro-sandblasting to re-open porosity and guarantee breathability of surfaces | - |
2. Masonry Repair | Fill joints and damaged areas with compatible lime mortar | 10–20 mm |
3. Bond Coat (Rough Cast) | Improves adhesion, balances absorption | 5–10 mm |
4. Base / Leveling Plaster | Main coat for levelling and moisture buffering | 15–25 mm |
5. Dehumidifying / Restoration Layer (if needed) | Open-pore layer for salt management | 20–30 mm |
6. Finish Coat | Smooth or textured lime finish | 3–5 mm |
7. Breathable Paint / Limewash | Final surface protection | Thin layer, multiple coats |
Not all limes are true limes!
Lime is a binder, produced by cooking chalky stones. It is used for construction limes, plasters, renders, finishing and building decoration. By cooking it is produced BURNT LIME (quicklime).
Different types of Lime:
1. HYDRATED LIME
Slaked by water: SLAKED LIME – COMMON LIME With more water: LIME PASTE – LIMEWATER
2. NATURAL HYDRAULIC LIME Common lime with hydraulic qualities
Others: HL - Hydraylic Lime LIC - Hydraulic Bond for Construction
EN 459–1 NORM : “Construction Limes – "Specifications and conformity criteria" 1/9/2002
4. Key Physical and Environmental Properties
Property | Typical Range | Why It Matters |
Vapour Resistance (μ) | 3–6 | Enables evaporation, prevents condensation |
Porosity | ≥ 40% | Traps salts and maintains breathability |
Thermal Conductivity (λ) | 0.3–0.5 W/m·K | Thermal buffer for stable interiors |
Capillary Absorption | ≤ 0.3 kg/m²·h⁰·⁵ | Limits liquid water penetration |
Compressive Strength | 1.5–5 MPa | Compatible with soft masonry |
Fire Reaction | Class A1 (non-combustible) | Meets EN 13501-1 |
VOC Emissions | Very Low / EC1 Plus equivalent | Promotes healthy interiors |
5. Mechanism of Breathability and Salt Resistance
- Lime plaster has a micro-porous structure that allows vapour diffusion while blocking liquid water.
- Salt crystals form in the plaster, not inside masonry, protecting the wall substrate.
- Carbonation reabsorbs CO₂, stabilizing the matrix and improving longevity.
- Natural alkalinity (pH > 12) makes lime inherently bacteriostatic and fungistatic, reducing mould growth.
6. Role in Heritage and Restoration
Challenge | Lime Plaster Response |
Salt efflorescence and rising damp | Vapour-open structure allows evaporation; salts migrate to plaster surface (sacrificial behaviour). |
Material compatibility | Elastic modulus and strength match historic masonry, avoiding cracking. |
Cement damage reversal | Replacing cement renders restores moisture balance and prevents trapped damp. |
Aesthetic continuity | Accepts natural pigments and patina; visually consistent with original architecture. |
Reversibility | Can be safely removed or re-worked without damaging the substrate. |
7. Testing and Quality Standards
Standard / Guideline | Scope / Application |
EN 459-1 | Building lime — classification and testing |
EN 998-1 / 998-2 | Mortars for plastering and masonry |
WTA 2-9-04/D | Restoration plaster systems (Europe) |
ISO 846 | Resistance to microbial growth |
ASTM C28 / C270 | Mortar composition and performance |
EN 13501-1 | Fire classification (A1) |
ICCROM / Getty | Conservation ethics and compatibility framework |
FLL Guidelines | Environmental integration of mineral materials |
8. Practical QA / Site Checklist
Inspection Area | Status | Remarks |
Wall condition before plaster removal | ☐ | |
Presence of salts or damp (moisture map) | ☐ | |
Type and integrity of substrate masonry | ☐ | |
Ambient temperature and humidity during application | ☐ | |
Layer thickness and coverage uniformity | ☐ | |
Carbonation and curing conditions | ☐ | |
Visual inspection after 28-day curing | ☐ |
9. Sustainability Insights
Aspect | Impact |
Embodied Energy | 30–40% lower than Portland cement renders |
Carbon Footprint | Partial CO₂ reabsorption via carbonation |
Lifecycle | 50+ years with proper maintenance |
End-of-Life | Fully recyclable and inert |
Certifications | Contributes to LEED / IGBC credits under Indoor Air Quality and Material Transparency |
10. Specification Template (Generic)
Lime plaster system comprising natural hydraulic lime mortar conforming to EN 459-1, applied in multiple coats over prepared masonry. The system shall include a vapour-open base coat, restoration coat where required, and a breathable lime finish or paint. Application and curing shall follow WTA 2-9-04/D guidelines. Mock-ups and on-site tests (adhesion, absorption, moisture) shall be approved prior to full execution.
11. Key Takeaway
Lime plaster represents the balance between material science and ecology — a natural system that protects, breathes, and heals masonry while supporting the broader goals of sustainability and heritage conservation.