The brick repair DENVER blog
At Brick Repair Denver, accurate mortar analysis is crucial to preserving the integrity of the historic buildings we work on. Understanding the original mortar composition allows us to create a repointing mortar that matches not just visually but also in terms of strength, permeability, and compatibility with the masonry. Wet-Chemical Methods One of the primary techniques we use is the wet-chemical method, specifically acid digestion. This process involves crushing a mortar sample and mixing it with a dilute acid. The acid dissolves carbonate-containing minerals from the binder and aggregate materials, leaving behind the sand and any acid-insoluble materials. This method is efficient and relatively inexpensive. It helps us understand the texture and color of the sand, which is vital for achieving a good visual match with the existing mortar. For more detailed information, we sometimes use variations of the acid digestion method that involve collecting the carbon dioxide gas released during the process. This allows us to accurately determine the carbonate content in the mortar, providing deeper insights into the binder composition. Instrumental Analysis For more complex projects, especially those involving historically significant structures, we employ instrumental analysis methods. These include polarized light or thin-section microscopy, scanning electron microscopy (SEM), atomic absorption spectroscopy (AAS), and X-ray diffraction (XRD). Among these, thin-section microscopy is commonly used. By examining thin slices of mortar under transmitted light, we can detect specific aggregates like carbonate-based materials that may not be fully revealed through chemical tests. Although instrumental methods require specialized equipment and expertise, they provide comprehensive information about the original mortar composition. This is especially useful when dealing with complex historic mortars that may include locally sourced materials or unconventional aggregates like crushed shells or natural cements. The Challenge of Historic Mortars
One of the challenges in mortar analysis is the variability of historic materials. Unlike modern mortars, which follow specific standards, historic mortars were often mixed on-site using local materials. As a result, they can vary greatly from one building to another, even within the same region. To address this, we combine both wet-chemical and instrumental analysis methods when needed. This approach gives us a clearer picture of the original materials used and helps us replicate the historic mortar as accurately as possible. Why Mortar Analysis Matters The goal of mortar analysis is to create a repointing mortar that is sympathetic to the original structure. If the new mortar is too hard, it can cause stress and damage the masonry. Conversely, if it's too soft or impermeable, moisture can build up and lead to issues like spalling or efflorescence. By understanding the original mortar, we ensure the new material supports the masonry rather than working against it. Whether we're working on a century-old Denver brick home or a Colorado historic landmark, our detailed mortar analysis ensures the longevity and aesthetic integrity of the buildings we restore. Finding the Right Mortar Match in Denver: Brick Repair Denver's Guide to Successful Repointing9/28/2024
When it comes to preserving historic buildings in Denver, finding an appropriate mortar match is critical. Repointing, the process of renewing the external part of mortar joints in masonry restortion and preservation, must be done with careful attention to the building’s original materials and design. The wrong mortar choice can cause serious damage to the structure by being too strong or too impermeable to moisture. Here’s what you need to know to ensure your repointing work is both physically and visually appropriate for your building. Do Your Research Before starting any repointing work, it’s essential to research and analyze the existing mortar and masonry materials. By examining unweathered portions of the historic mortar, you can determine the appropriate mix for your new mortar. This is important because new mortar must not be stronger or less permeable than the original to avoid damaging the building. Take time to examine the masonry units themselves—whether brick, stone, or terra cotta—and understand the original construction techniques. A simple, non-technical evaluation of the masonry and mortar can reveal valuable information about the strength and permeability of both. This helps ensure that the new mortar will blend with the original in both function and appearance. The Role of Mortar Analysis For masonry buildings of special historical significance, it might be beneficial to have a qualified masonry contractor who can conduct a mortar analysis. While this can help identify the ingredients of the original mortar, it’s not foolproof. Factors such as the original water content, curing rate, and even the weather conditions, especialy in Colorado, during construction can’t be determined by lab results alone. The most helpful information from laboratory mortar analysis is often the identification of the sand used—its gradation and color—which is critical for achieving a good color and texture match in the new mortar.
Why Mortar Strength Isn’t Always a Good Thing
A common misconception is that stronger mortars are better. In reality, when repointing historic buildings, the mortar should be softer and more permeable than the masonry units. This is because stresses within a wall—caused by expansion, contraction, or moisture migration—need to be relieved by the mortar, not the masonry. A mortar that’s stronger than the masonry will force these stresses onto the masonry units, potentially causing irreversible damage. High lime mortars, though often softer, allow for higher permeability and can accommodate the building’s natural movements over time. So, stop using Type S and high cementitious cement fro repoinitng on historical brick and stone buildings in Denver. The Components of Mortar: What You Need to Know The main ingredients of mortar are sand, lime, water, and sometimes Portland cement. Each plays a crucial role in the mortar’s properties.
Modern Additives: Use with Caution While modern chemical additives can be helpful in certain situations, they aren’t always appropriate for historic masonry. For example, air-entraining agents can improve resistance to freeze-thaw cycles, but other additives, such as antifreeze compounds or bonding agents, can introduce new problems like efflorescence or poor bonding to the masonry. It’s best to avoid unnecessary chemicals and instead focus on proper mortar composition and joint preparation. Conclusion In repointing historic buildings in Denver, the goal is to create a mortar that works in harmony with the original materials. Whether you’re restoring a century-old home or a landmark building, understanding the composition and role of mortar is key to maintaining the structure’s integrity. With careful research, analysis, and attention to detail, you can ensure that your repointing work not only protects the building but also preserves its historical beauty for generations to come. If you'd prefer to hire a specialist in masonry restorartion, to ensure your historic building is repointed with the proper mortar, reach out to Brick Repair Denver 720-445-9474 |
AuthorJesse Smith, Owner and Architectural Conservator at Brick Repair Denver, draws on generations of expertise in heritage masonry preservation and shares his knowledge with a direct, no-nonsense approach. ArchivesCategories |
Denver's leading professional masonry restoration services since 1942.
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We carry out searches to ensure the correct and most suitable lime and sand aggregates are used in both re-build and restoration projects. We use traditional methods of restoration and conservation to breathe life back into your home or building. We aim to restore using similar materials and methods to ensure longevity to the original fabric. Need Repairs? (720) 445-9474
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