Best Mortar Mix for Repointing Brickwork
Repointing brickwork maintains the integrity and appearance of brick structures. Choosing the right mortar mix is essential for ensuring durability, weather resistance and compatibility with existing materials.
We explore the best mortar mix options for brick repointing for this feature. We discover the ideal ratios of cement, lime and sand, and discuss mixing techniques that improve performance.
What is the Best Repointing Brick Mortar Mix?
Understanding the different mortar types is crucial for successful repointing. They each have distinct properties and applications. This section explores these mortar types, their compositions and their suitability for repointing brickwork.
What is Type N mortar?
Composition: 1 part Portland cement, 1 part lime and 6 parts sand
Compressive strength: 750 pounds per square inch (psi); 5.2 megapascals (MPa)
Type N mortar is the most versatile and best mortar mix for repointing. It offers a good balance between strength and flexibility, making it suitable for a range of brickwork applications.
The lime mortar mix ratio for repointing offers excellent workability and water retention. This is important for proper curing in repointing work. Type N is a highly suitable pointing mortar because of its medium strength and works well with existing brickwork.
It accommodates minor building movement without cracking and is compatible with various brick types. This mortar type also allows for some moisture movement, reducing the risk of trapped moisture.
What is Type O mortar?
Composition: 1 part Portland cement, 2 parts lime and 9 parts sand
Compressive strength: 350 psi (2.4 MPa)
Type O mortar is the weakest and is known for its high lime content. This composition creates a soft, flexible mortar that is highly workable. It is suitable for specific repointing applications, particularly for soft, historic bricks or stone.
This type is highly breathable, allowing for excellent moisture transmission and is less likely to cause damage to softer masonry. However, it is not suitable for areas with high moisture exposure or freeze-thaw cycles.
Type O may also not provide adequate strength for modern brickwork or areas subject to high stress.
What is Type S mortar?
Composition: 1 part Portland cement, 1/2 part lime and 4 1/2 parts sand
Compressive strength: 1,800 psi (12.4 MPa)
Type S mortar is stronger than Types N and O. It offers high bond strength and is often used in below-grade applications or where additional strength is needed. This mortar type is suitable for repointing with caution.
It can be used in high-stress areas, such as in newer brickwork or severe weather exposure conditions. However, Type S may be too strong for many existing structures, potentially causing damage to softer bricks.
Overall, it is less flexible than Type N, which may lead to cracking in cases of building movement. Type S mortar mix for pointing should be used carefully and only when the existing brickwork can accommodate its strength.
What is Type M mortar?
Composition: 1 part Portland cement, 1/4 part lime and 3 parts sand
Compressive strength: 2,500 psi (17.2 MPa)
Type M mortar is the strongest of the 4 types. It is primarily used in heavy-load-bearing walls, foundations and hardscape applications and is generally not recommended for repointing. It is too strong for most repointing applications.
This type carries a high risk of causing damage to existing brickwork, especially in older or softer bricks. Type M lacks the flexibility needed to accommodate building movement.
It also has poor water retention properties, which may lead to rapid drying and poor bond formation. Type M may create a moisture barrier, trapping water within the brickwork and causing deterioration.
Learn advanced top tips on how to mix mortar for repointing with our detailed guide.
Best Applications for Mortar Types in Brick Repointing
As outlined above, different mortar types offer varying levels of compressive strength, making them suitable for specific repointing applications. Here, we explore the best uses for how to repoint brick with all mortar types.
When to use Type N mortar
- Exterior above-grade walls under normal loading conditions
- Interior load-bearing walls in most structures
- Soft stone masonry repointing, such as limestone or sandstone
- General use in buildings and homes in areas with moderate weather exposure
- Historic building restoration projects
Type O mortar applications
- Interior non-load-bearing walls
- Repointing of historic masonry originally built with lime mortar
- Extremely soft stone or brick where other mortars might damage the masonry
- Decorative, non-structural masonry such as fireplace facings or garden walls
- Buildings in areas with minimal weather exposure and loading requirements
Type S mortar applications
- At-grade exterior walls in areas with severe frost action
- Load-bearing walls in smaller structures
- Masonry structures subject to normal loading and moderate wind pressures
- Patios, walkways and other outdoor masonry exposed to freeze-thaw cycles
- Chimneys and fireplaces because of good resistance to heat and moisture
Type M mortar applications
- Below-grade walls and foundations exposed to soil pressure
- Load-bearing walls in multi storey buildings
- Severe weather exposure areas, especially those prone to high winds
- Parapets, retaining walls and other structures subject to high stress
- Masonry in contact with earth, such as manholes and sewers
Make Your Brick Repointing Jobs Even Better with Premium Mortar
Building Materials Nationwide offers a comprehensive range of brick repointing mortar mixes to suit various restoration and construction needs. Our selection includes both traditional mortars and cement-based options, ensuring compatibility with different types of brickwork. We supply premixed dry mortars for convenience, as well as individual components for custom blending on-site.
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