Brick walls and chimneys are durable and built to last, thanks to strong mortar joints. Repair and seal cracked mortar as soon as you discover it. Otherwise, a small problem today could become a major headache and expense.
How Mortar Deteriorates
Mortar joints are designed to take most of the damage to a brick wall, cracking and deteriorating before bricks do. Common causes behind mortar damage include:
- Age and natural weathering
- Foundation settlement
- Freeze-thaw cycles
- Structural movement
- Water infiltration
Mortar damage manifests itself in similar ways, regardless of the cause. You should watch closely for signs like visible cracks, crumbling or powdery mortar, gaps between bricks, and water stains on any interior walls.
Preparing for Mortar Repair
Gather these tools and the proper safety equipment before you proceed:
- Mortar mix or mortar joint sealant
- Chisel
- Hammer
- Caulk gun (for sealant application)
- Trowel
- Utility knife
- Waterproof gloves
- Safety glasses
Make sure your work area is clean and well-ventilated. Also, check your thermometer before starting. Mortar joint sealant is temperature-sensitive. You should only apply it when it’s above 50 degrees.
The Mortar Repair Process
Repairing or sealing mortar takes only three steps.
Step 1: Prep the Surface
Start by using a hammer and chisel to widen the crack to 1/4 of an inch. Remove any damaged concrete. Ensure the crack’s edges look like an inverted V. Brush away any loose material.
Step 2: Apply the Sealant or Mortar
For minor jobs using sealant, cut the nozzle tip of the sealant tube at an angle. Make sure the opening on the tube matches the width of the crack. Load the tube in a standard caulk gun and slowly force a bead deep into the crack. Mortar joint sealant is flexible and can stretch up to 700% against wall movement and temperature changes.
For larger jobs, you may need to mix traditional mortar yourself. Follow the manufacturer’s instructions for mixing ratios, and add water gradually until you get the right consistency and a smooth, workable texture. Dampen the repair area slightly to improve adhesion. Use a trowel to press the mortar firmly into the joint, and ensure you have no air pockets.
Step 3: Finishing the Repair
After applying the mortar or sealant, use your trowel to remove excess material and match the surrounding surface texture. If you use sealant, let the surface dry for two hours.
Traditional mortar needs a few days of damp conditions to set. Clean any smears from the brick faces using a damp cloth, and protect the area from direct sunlight and extreme temperatures.
When To Call a Professional
While many mortar repairs can be DIY projects, these specific situations call for professional expertise:
- Extensive damage covering large areas
- Historic or heritage buildings requiring specialized care
- Lack of confidence in personal DIY skills
- Structural concerns or foundation issues
Professional masons have the experience and tools to handle complex repairs and keep mortar joints looking their best.
