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Historic Lime-Based Mortars Versus Modern Mortars

Historically, lime-based mortars were commonly used in construction due to their flexibility, breathability, and self-healing characteristics1. Lime mortar, composed of lime and an aggregate such as sand mixed with water, is one of the oldest known types of mortar2. The reasons for using lime in mortar 2000 years ago still remain valid today3.

 

On the other hand, modern mortars often use Portland cement, which is harder and less flexible than lime. While this might seem like an advantage, it can cause problems in older buildings, particularly those built with soft bricks or stones. The hardness of cement can lead to cracking and damage over time4.

 

The Importance of the Appropriate Mortar Mix

Choosing the right mortar mix is crucial for the longevity and appearance of the structure. Using a mortar that is too hard can damage the bricks or stones, while a mix that is too soft may not provide the necessary strength or durability5. The key is to match the mortar's hardness to the material it's binding. For historic buildings, a lime-based mortar is often the best choice1.

 

Matching Materials and Pigments for Aesthetically Pleasing Outcomes

In addition to the functional aspects of mortar, there's also an aesthetic component to consider. When repointing a brick or stone structure, it's essential to match the existing mortar in color, texture, and composition. This ensures a cohesive and visually appealing outcome6.

 

The Role of Workmanship in Masonry Preservation

The quality of workmanship plays a significant role in both the functionality and aesthetics of masonry preservation. Poor application can lead to damage to the masonry and negatively affect the final mortar joint finish quality4. Therefore, hiring experienced and skilled professionals is crucial.

 

Alliance Restoration is a Kansas City contractor that understands these nuances and provides high-quality repointing services. Their team of experts is well-versed in both historic lime-based mortars and modern mortars, ensuring the right mix for your specific project. They also appreciate the importance of matching materials and pigments to create visually appealing outcomes and place a strong emphasis on the quality of workmanship to prevent damage and ensure a high-quality finish.

 

In conclusion, brick and stone repointing is an essential part of preserving and maintaining masonry structures. Understanding the differences between historic lime-based mortars and modern mortars, choosing the appropriate mortar mix, using matching materials and pigments, and ensuring high-quality workmanship are all important factors in this process.

 

Footnotes

1. https://www.nps.gov/articles/000/podcast-033-historic-uses-of-lime-mortar-and-its-continuing-importance-today.htm ↩ ↩2

    

2. https://en.wikipedia.org/wiki/Lime_mortar ↩

    

3. https://www.graymont.com/en/markets/building-construction/mortar/history-lime-mortar ↩

    

4. https://cornishlime.co.uk/articles/the-difference-between-lime-cement-mortars/ ↩ ↩2

    

5. https://www.limeworks.us/differences-repointing-natural-hydraulic-lime-nhl-mortars-vs-cement-based-mortars-faq/ ↩

    

6. https://www.ids-dmv.com/masonry/top-5-ways-to-tell-if-brick-mortar-is-historic-or-contemporary/ ↩