What Type Of Mortar For Brick Repointing

What Type of Mortar for Brick Repointing? A Comprehensive Guide

Choosing the right mortar for brick repointing is crucial for the longevity and aesthetic appeal of your brickwork. Using the incorrect type can lead to problems like cracking, crumbling, and even structural damage. This guide will delve into the different types of mortar available and help you select the best option for your repointing project. We'll cover everything from understanding mortar mixes to considering the specific needs of your brickwork.

Understanding Mortar Types and Their Properties

Mortar is a mixture of cement, lime, sand, and water. The proportions of these ingredients determine the mortar's properties, including its strength, workability, and durability. Common types of mortar are classified using a numerical system, often referred to as the British Standard (BS) system, although variations exist in other regions. Each number signifies a different mix ratio and resulting properties:

• Type N (Normal Strength): This is a general-purpose mortar, suitable for many applications, offering a balance between strength and workability. It's commonly used for general bricklaying and some repointing projects, particularly for buildings that don't require high strength mortar.

• Type S (Medium Strength): Type S mortar offers increased strength compared to Type N, making it ideal for projects where more structural integrity is required. It's often chosen for load-bearing walls and areas subjected to significant stress.

• Type M (High Strength): This is the strongest type of mortar, suited for applications demanding exceptional durability and load-bearing capacity. It’s less commonly used for repointing unless the brickwork is under extreme stress or needs significant structural reinforcement.

• Type O (Low Strength): Type O mortar is a more flexible and permeable mortar, particularly suitable for heritage buildings and older structures. Its lower strength allows it to move with the building's natural settlement, minimizing the risk of cracking. It's often preferred for repointing historic brickwork.

• Lime Mortars: Lime mortars are historically accurate and are often preferred for repairing older brick structures. They are more flexible and permeable than cement-based mortars, which reduces the risk of damage from movement and allows moisture to escape, preventing dampness. Different types of lime mortars exist, including NHL (Natural Hydraulic Lime) and NHL-based mortars.

Choosing the Right Mortar for Your Repointing Project

The best type of mortar for your brick repointing project depends on several factors:

1. Age and Type of Brickwork:

• Older buildings: Often benefit from using a lime-based mortar or a Type O mortar to match the original mortar and minimize the risk of cracking. This is crucial for preserving the building's historic character and structural integrity.
• Modern buildings: Can usually tolerate stronger mortars like Type N or Type S, depending on the load-bearing requirements.

2. Location and Exposure:

• Exposed locations: May require a stronger mortar (Type S or M) to withstand harsh weather conditions.
• Sheltered locations: Can use a less strong mortar, such as Type N or even a lime mortar.

3. Structural Integrity:

• Load-bearing walls: Should always use a high-strength mortar (Type S or M) to ensure structural stability.
• Non-load-bearing walls: Can use a less strong mortar depending on other factors mentioned above.

4. Matching Existing Mortar:

Ideally, the new mortar should closely match the color and texture of the existing mortar to maintain the aesthetic appearance of the brickwork. This might involve using specific pigments or additives to achieve the desired color.

Important Considerations:

• Color Matching: Obtain samples of mortar from reputable suppliers to ensure the color matches the existing mortar.
• Workability: Choose a mortar that is easy to work with and can be effectively applied to the joints.
• Durability: Select a mortar that is resistant to weathering, frost, and other environmental factors.
• Professional Advice: For complex repointing projects or historic buildings, consult with a qualified bricklayer or building conservator to ensure the correct mortar is used and the work is carried out correctly.

By carefully considering these factors and choosing the appropriate mortar, you can ensure that your brick repointing project is both successful and long-lasting. Remember that selecting the correct mortar type is only one part of the process; proper preparation, application, and curing techniques are also essential for a successful outcome.