Lime Plasters

• 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
• Disclaimer

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

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

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

8. Practical QA / Site Checklist

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.

Disclaimer

Conix is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.