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Pros of Plastering and Building with Lime Mortar:

1. Breathability

• Description: Lime mortar is highly breathable, meaning it allows moisture to move through walls, preventing the buildup of dampness within structures.

• Benefit: This helps in regulating internal humidity and reduces the risk of mold and rot, especially in older buildings or in areas with high moisture content like exposed coastal regions.

2. Flexibility

• Description: Lime mortar is more flexible than cement-based mortars, allowing for small movements in the building structure without cracking.

• Benefit: This makes it ideal for use in historic buildings, where materials may expand and contract due to seasonal changes or settling.

3. Carbon Sequestration

• Description: Lime absorbs carbon dioxide from the air as it hardens (carbonation process). This process continues slowly over time.

• Benefit: Using lime mortar can have a net positive environmental impact as it captures and locks in CO2, making it a more sustainable option compared to cement, which is highly carbon-intensive to produce.

4. Repair and Restoration

• Description: Lime mortar is commonly used in the restoration of historic buildings due to its compatibility with older materials like stone and brick.

• Benefit: Lime mortar is less likely to damage original building materials, as it is softer and can be more easily removed or replaced without compromising the integrity of the original structure.

5. Aesthetic Qualities

• Description: Lime-based plasters and finishes can be mixed to produce a wide range of textures and colors.

• Benefit: It gives a warm, traditional look that is sought after in heritage restoration projects. The natural finish also gives a more organic, 'living' appearance that can enhance the character of a building.

6. Longevity and Durability

• Description: When properly applied, lime mortar can last for hundreds of years, especially when used in dry climates or well-maintained buildings.

• Benefit: It is resistant to weathering, and its self-healing properties allow it to repair small cracks that may form over time.

7. Workability

• Description: Lime mortar is easy to work with in terms of mixing and application.

• Benefit: It provides ample working time before setting (unlike rapid-setting modern cements), which is advantageous for craftsmen and builders who need to make adjustments during application.

8. Thermal Insulation

• Description: Lime-based construction provides better thermal insulation than cement-based systems, especially when combined with materials like hemp or limecrete.

• Benefit: This improves the energy efficiency of buildings, maintaining a more stable internal temperature in both hot and cold weather.

9. Non-toxic and Healthier

• Description: Lime is non-toxic, unlike some modern construction materials that may contain harmful chemicals like VOCs (volatile organic compounds).

• Benefit: It promotes a healthier indoor environment, which can be beneficial for residents with respiratory issues or sensitivities.

Cons of Plastering and Building with Lime Mortar:

1. Longer Setting Time

• Description: Lime mortar takes much longer to cure and set compared to cement mortar.

• Drawback: This can slow down construction or restoration projects, especially when speed is a priority. It requires a longer time for the plaster or mortar to reach full strength.

2. Weather Sensitivity

• Description: Lime mortar is sensitive to extreme weather conditions, especially freezing temperatures.

• Drawback: It is not ideal for application in very cold conditions, as the curing process can be hindered by frost. This can be mitigated by using additives or waiting for milder weather, but it does require careful planning.

3. Higher Initial Cost

• Description: While lime mortar itself may not be prohibitively expensive, the cost of lime-based plasters and products can sometimes be higher than cement-based options.

• Drawback: In addition, labour costs may be higher due to the specialized knowledge and skills required for proper application. Therefore, upfront costs can be significant, particularly in large-scale projects.

4. More Labor-Intensive

• Description: Lime mortar applications are often more labour-intensive than cement mortars due to the care required in mixing, application, and curing.

• Drawback: The skills required to apply lime mortar effectively are less common than those for cement mortars, and untrained workers may produce subpar results, leading to potential repair costs later.

5. Less Strength than Cement Mortar

• Description: Lime mortar is softer and has less compressive strength than cement mortar.

• Drawback: While this is beneficial for historic buildings that need to flex, it may not be ideal for structures that require a high-strength bond, such as modern buildings or load-bearing walls in certain environments.

6. Requires Proper Maintenance

• Description: Lime mortar needs to be properly maintained, especially if exposed to wet conditions or high foot traffic.

• Drawback: Without regular attention, lime mortar joints may deteriorate faster than modern materials, requiring periodic re-pointing or re-plastering.

7. Salts and Efflorescence

• Description: When a building using lime mortar has been exposed to moisture, salts can leach out of the materials and create a white, powdery deposit known as efflorescence.

• Drawback: This is particularly common in walls that have absorbed water and then dried out. While efflorescence is usually just aesthetic, it can sometimes be a sign of ongoing moisture problems. In more severe cases, salts can also contribute to the deterioration of the mortar or building materials, leading to potential long-term issues if the moisture source isn't addressed.

8. Vulnerability to Water Ingress

• Description: While lime mortar is breathable and allows moisture to escape, if the building envelope is not properly designed or insufficiently maintained, water can enter the structure and cause damage.

• Drawback: Without the building envelope being free from water ingress, for example compromised roofing, drainage systems and incorrect ground/floor levels, water penetration can lead to damp walls and the erosion of lime mortars over time.

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