The type of mortar used for brick pointing depends primarily on the age and strength of the original brickwork. While several mortar types exist, Type O and Type N are commonly used for repointing projects.
Understanding Mortar Types for Repointing
Choosing the correct mortar for repointing is crucial to prevent damage to the existing bricks and ensure the longevity of the repair. Using a mortar that is stronger than the original can cause the bricks themselves to crack or spall as the structure settles or experiences thermal expansion.
Type O Mortar for Older Brickwork
As stated in the reference, Type O mortar often is used for repointing older brickwork. Older brickwork, particularly that found in historic buildings, typically used softer bricks and weaker lime-based mortars. Type O mortar is a low-strength mortar with a high lime content, making it flexible and less likely to damage softer, older bricks.
- Characteristics:
- Low compressive strength
- High lime content
- More flexible than stronger mortars
- Best Use Case: Repointing historic buildings and older brick walls constructed with soft bricks and weaker original mortar.
Type N Mortar for Newer Brickwork
The reference also notes that Type N mortar may be suitable for repointing newer brickwork. Modern brick construction often utilizes harder bricks and stronger cement-based mortars. Type N mortar is a medium-strength mortar, stronger than Type O but still relatively versatile, making it appropriate for repointing more robust, newer brickwork.
- Characteristics:
- Medium compressive strength
- Balanced mix of cement, lime, and sand
- Suitable for many general masonry applications
- Best Use Case: Repointing contemporary or newer brick walls built with harder bricks and stronger original mortar.
Selecting the Right Mortar
Choosing between Type O and Type N (or potentially other types like Type S or M in specific structural situations) requires careful consideration. It's often recommended to match the strength and composition of the new pointing mortar to the original mortar as closely as possible. A simple scratch test or laboratory analysis can help determine the existing mortar's characteristics.
Mortar Types for Repointing Summary
| Mortar Type | Compressive Strength | Best Used For |
|---|---|---|
| Type O | Low | Older, soft brickwork |
| Type N | Medium | Newer, harder brickwork |
Note: Consulting with a masonry professional is highly recommended to ensure the correct mortar type is selected for your specific brickwork project.
