At Pro Mason Supply, we understand the importance of using the right materials for your masonry projects, especially when it comes to preserving the integrity and beauty of historic structures. That's why we proudly offer a range of pure Natural Hydraulic Lime (PHL) mortars, specifically formulated for breathability, flexibility, and long-term performance. Our ProMason Lime Mortars, available in PHL 2.0, 3.5, and 5.0 strength ratings, contain absolutely no Portland cement, ensuring an authentic and compatible repair for your valuable stonework and brickwork.
This guide will walk you through the best practices for mixing and using ProMason Lime Mortar, helping you achieve professional-quality results that will stand the test of time.
Understanding ProMason Lime Mortar Components
Our ProMason Lime Mortar system is based on a simple yet effective ratio of three key components:
- ProMason Lime Concentrate (1 part): This is the heart of our mortar, a pure Natural Hydraulic Lime (PHL) chosen for its specific strength and performance characteristics.
- Local Sand (2-3 parts): The aggregate provides bulk and texture to the mortar. The type and grading of your local sand will influence the final look and workability. We generally recommend a clean, well-graded sand. The ratio of sand can be adjusted within this range to achieve the desired consistency and workability.
- Water: Added gradually, water activates the hydraulic lime and creates a workable paste.
Mixing Your ProMason Lime Mortar
Achieving the right consistency is crucial for successful application. Follow these steps for mixing your ProMason Lime Mortar:
- Combine Dry Ingredients: In a clean mixing tub or on a mixing board, thoroughly blend one part ProMason Lime Concentrate with two to three parts of your chosen sand. Mix until a uniform color is achieved.
- Add Water Gradually: Slowly add clean water to the dry mixture, mixing continuously with a trowel or mixing paddle. The goal is to create a stiff but workable mortar – similar to a thick paste or shaving cream. Avoid adding too much water at once, as this can lead to a weak and soupy mix.
- Test for Workability: The mortar should hold its shape on a trowel without slumping excessively. It should be cohesive and easy to apply to the joints. You may need to adjust the water content slightly to achieve the ideal consistency for your specific sand and working conditions.
Best Practices for Repointing with Lime Mortar
Proper preparation and application are essential for a durable and aesthetically pleasing repair.
- Carefully Remove Old Mortar: Using hand tools such as chisels and scrapers, carefully remove the deteriorated mortar from the joints to a depth of approximately 2 to 2.5 times the width of the joint. Take care not to damage the surrounding brick or stone. Avoid using power tools that can vibrate and damage the historic masonry.
- Prepare the Joints: Once the old mortar is removed, thoroughly brush the joints to remove any loose debris and dust. Next, dampen the joints with clean water using a brush or spray bottle. This helps the new mortar bond properly to the existing masonry and prevents it from drying out too quickly. The surface should be damp but not saturated.
- Apply the New Mortar: Using a pointing trowel, carefully apply the ProMason Lime Mortar into the prepared joints. Work in small sections and ensure the mortar is fully compressed into the joint, eliminating any voids. For wider joints, apply the mortar in layers, allowing each layer to firm up slightly before applying the next.
- Tool the Joints: Allow the mortar to dry until it reaches the "thumbprint hard" stage – meaning you can press your thumb lightly onto the mortar and leave a slight indentation without it being overly soft or wet. At this point, tool the joints to match the original profile or your desired aesthetic. Use a brick jointer for concave or V-shaped joints, a flat metal slicker for flush joints, or the end of a hardwood dowel for a more rustic, aged appearance. The timing of tooling is critical; if done too early, the mortar will smear, and if done too late, it will be too hard to shape.
- Curing is Key: Proper curing is paramount for the strength and longevity of pure lime mortar. In warm weather, and ideally in all conditions, gently cover the newly pointed areas with damp burlap cloth. This helps to retain moisture. In very warm and dry conditions, you can cover the burlap with plastic sheeting to further slow down the drying process. Keep the mortar as damp as possible for a minimum of 5-7 days by regularly misting the burlap with water. This slow curing process allows the lime to carbonate properly, resulting in a strong and durable mortar.
The Importance of Authentic Lime Mortar for Historic Structures
Traditional buildings constructed before the early 1900s were typically built using lime-based mortars. These mortars are softer and more flexible than modern Portland cement-based mortars, allowing the building to breathe and accommodate slight movements over time without cracking.
Using a harder Portland-based mortar like Type O or Type N for repointing these historic structures can lead to significant problems. The harder mortar can trap moisture within the masonry, leading to freeze-thaw damage, spalling of the brick or stone, and ultimately, structural issues. The incompatibility in flexibility can also cause the softer historic bricks or stones to crack under stress.
For more modern structures, especially those built after 1940 where Portland-based mortars were commonly used, a softer Type O or Type N mortar might be more appropriate for repointing.
At Pro Mason Supply, we are dedicated to providing you with the highest quality lime mortars and the knowledge you need to successfully restore and maintain your masonry structures. Choose ProMason Lime Mortar for an authentic, breathable, and long-lasting solution. Contact us today for expert advice and to find the right PHL mortar for your project.