The primary way to bond bricks together is with mortar, a thick, workable paste used to bind construction blocks such as bricks, concrete blocks, and stone.
What is Mortar?
Mortar is essentially a "glue" made from:
- Cement: The binding agent. Portland cement is commonly used.
- Fine Aggregate (Sand): Provides bulk, strength, and workability.
- Water: Activates the cement and creates a workable consistency.
- Lime (Optional): Improves workability, water retention, and bond strength, but is not always included.
The Mortar Mixing Process:
- Combine dry ingredients: Thoroughly mix the cement, sand, and any lime in a mortar pan or wheelbarrow.
- Add water gradually: Slowly add water while mixing, until the mortar reaches a plastic, workable consistency. It should be thick enough to hold its shape on a trowel but pliable enough to spread easily.
- Let it slake (optional): Allowing the mortar to sit for 15-30 minutes after mixing, called slaking, can improve its workability. Re-mix after slaking.
Applying the Mortar:
- Prepare the brick surface: Ensure the bricks are clean and free of debris. Dampening the bricks slightly before applying mortar can help prevent them from drying out the mortar too quickly.
- Apply mortar to the bed joint: Spread a layer of mortar on the surface where the first course of bricks will be laid. This is the bed joint.
- Apply mortar to the head joint: Apply mortar to the end of the brick that will be placed next to the previously laid brick. This is the head joint.
- Position the brick: Carefully place the brick, pressing it firmly into the mortar. Use a level to ensure it's aligned correctly.
- Remove excess mortar: Scrape away any excess mortar that squeezes out of the joints.
- Tool the joints: After the mortar has partially set, use a jointing tool to compress and shape the joints. This improves the appearance and weather resistance of the brickwork.
Types of Mortar:
Mortar is classified by strength, with different types suited for different applications:
| Mortar Type | Compressive Strength (PSI) | Typical Usage |
|---|---|---|
| Type M | 2500 | Heavy loads, below-grade (foundations) |
| Type S | 1800 | High wind/seismic areas, retaining walls |
| Type N | 750 | General use, above-grade exterior walls |
| Type O | 350 | Non-load-bearing interior walls, historic restoration |
| Type K | 75 | Very weak, not typically used in modern construction |
Note: Always consult local building codes and a structural engineer to determine the appropriate mortar type for your project.
