How Do You Put Mortar Between Bricks?

Putting mortar between bricks, whether for new construction or repairing existing walls (known as repointing or tuckpointing), is a fundamental skill in masonry that ensures structural integrity and weather resistance. The process involves careful preparation, precise application, and proper finishing techniques to create durable, aesthetically pleasing joints.

Understanding Mortar Joints and Their Importance

Mortar acts as both an adhesive and a cushion between bricks, allowing for slight movement while bonding the units together. It fills the gaps, preventing water penetration and contributing significantly to the wall's overall strength and stability. Proper mortar application is crucial for the longevity and performance of any brick structure.

Essential Tools and Materials

Having the right tools and materials is key to a successful mortar application.

For more detailed information on specific tools, you can refer to guides on masonry tools.

Step-by-Step Guide to Applying Mortar Between Bricks

The method for applying mortar differs slightly depending on whether you are laying new bricks or repairing existing mortar joints (repointing).

For New Bricklaying

When laying new bricks, mortar is applied as a bed for each brick and vertically between bricks (known as perpends).

1. Prepare the Mortar: Mix the dry mortar ingredients with water to a consistent, workable paste. It should be pliable but not soupy.
2. Lay the Mortar Bed: Using a brick trowel, spread a consistent bed of mortar on the foundation or the previous course of bricks.
3. Place the Brick: Carefully set the brick onto the mortar bed, wiggling it slightly to ensure good contact.
4. Butter the Ends: Apply mortar to the end of the next brick before placing it against the previous one to form the vertical joint (perpend).
5. Strike the Joints: Once several bricks are laid, use a jointing tool to compress and shape the mortar, creating a dense, weather-resistant finish.

For Repointing (Repairing Existing Mortar)

Repointing is the process of removing deteriorated mortar from between bricks and replacing it with new mortar. This is where precision and careful technique are paramount.

1. Preparation is Key:

   • Clean Out Old Mortar: Carefully remove all loose, cracked, or crumbling mortar from the joints using a hammer and chisel or a grinder with a masonry blade. Aim for a consistent depth, typically around half an inch to an inch.
   • Clean the Joints: Brush out any dust or debris from the cleaned-out joints using a wire brush.
   • Dampen the Area: You can use a heavy mist to dampen the wall and mortar joints down before applying the mortar. This critical step prevents the dry bricks from rapidly absorbing water from the new mortar, which could lead to poor adhesion and premature drying, compromising the mortar's strength.

2. Mix the Repointing Mortar:

   • Mix your mortar to a slightly stiffer consistency than for new bricklaying. It should be firm enough to stay on your trowel but still workable. The exact mix ratio depends on the original mortar and desired properties; consulting a guide on mortar types can be helpful.

3. Applying the Mortar:

   • Load Your Trowel: Place a small amount of prepared mortar onto your mortar hawk or directly onto a small pointing trowel.
   • Fill Vertical Joints First: Start by using a small sharp trowel and fill the cleaned-out joints with mortar. Begin by working on the vertical (perpend) joints. This makes it easier to clean up any excess mortar before tackling the horizontal joints. Push the mortar firmly into the joint.
   • Fill Horizontal Joints: After completing the vertical joints, move on to the horizontal bed joints. Use your pointing trowel to press the mortar into the joint.
   • Pack it Tightly: Pack the mortar in tightly, making sure there are no gaps or air holes. This is crucial for preventing water penetration and ensuring the longevity of the repair. Work the mortar into every crevice.

4. Finishing the Joints:

   • Tool the Joints: Once the mortar has stiffened slightly (thumbprint hard), use a jointing tool to compress and shape the new mortar. Apply firm, consistent pressure to create a durable, weather-tight joint that matches the existing brickwork's profile.
   • Clean Up: Immediately after tooling, lightly brush away any excess mortar crumbs from the brick faces with a soft-bristled brush. Avoid smearing wet mortar on the bricks.

5. Curing the Mortar:

   • Keep the newly repointed areas damp for at least 3-7 days after application. This slow curing process allows the mortar to achieve its maximum strength and durability. Lightly misting the wall periodically or covering it with plastic sheeting can aid in curing, especially in hot or dry conditions.

Tips for Success

• Weather Conditions: Avoid repointing in direct sunlight, high heat, or freezing temperatures. Ideal conditions are moderate temperatures (40-80°F / 5-27°C) with partial shade.
• Mortar Consistency: The right consistency is vital. Too wet, and it's weak; too dry, and it won't bond properly.
• Practice: If you're new to masonry, practice on a scrap piece of brick or an inconspicuous area first.
• Safety First: Always wear appropriate personal protective equipment, including gloves, eye protection, and a dust mask.

Common Mortar Joint Profiles

The final appearance of your mortar joints can vary. Common profiles include:

• Concave: A curved, indented joint made with a rounded tool. This is very popular and weather-resistant.
• V-Joint: A V-shaped indentation, also made with a V-shaped tool, offering good weather resistance.
• Flush: Mortar is flush with the brick face, often scraped off with a trowel. Less weather-resistant.
• Raked: Mortar is raked back from the brick face, creating a shadow line. Can collect water if not properly sloped.

By following these steps and paying attention to detail, you can effectively put mortar between bricks, ensuring a strong, durable, and attractive masonry structure.