Over time, moisture, thermal movement, and harsh weather can cause mortar joints in a brick chimney to deteriorate. Chimney repointing is the process of removing old mortar joints and replacing them with new mortar to restore structural integrity and prevent water damage. Unlike tuckpointing, which is cosmetic, repointing a chimney is essential for the functionality and safety of the structure. If neglected masonry joints are left unmaintained, you could be looking at chimney rebuilding or even a full rebuild of the exterior masonry.
Before You Repoint a Chimney
Before you start repointing a chimney, you need to inspect it. Look for signs of deterioration, such as loose mortar, cracks, spalling, or water damage on the surrounding brick. Repointing is a time-consuming process that requires patience and precision,, so using the right tools is key. You will need a plugging chisel, hammer, tuck pointer, pointing tools, spray bottle, wire brush, and mortar mixer. Wear protective gear to avoid falling debris and dust inhalation.
Remove Old Mortar
The first step in repointing a chimney is removing the old mortar from the damaged joints. Use a plugging chisel and hammer to chip away the old mortar to a depth of 1-2 inches. Be careful not to damage the surrounding brickwork, as older bricks can be fragile. Use a wire brush or compressed air to clear out any remaining dust and debris so the new mortar can bond properly.
Mix and Apply
You need to choose the right mortar. For masonry repairs on an old brick chimney, a lime mortar mix of lime putty, sand, and water is often recommended, as it allows for more flexibility and breathability. Newer masonry structures may require a cement-based mortar. Follow a step-by-step guide to mix the mortar, gradually adding water until you get the right consistency. Use a spray bottle to mist the cleaned joints lightly so the new mortar bonds better.
Apply the new mortar with a tuck pointer and press it in small lifts into the joints. Fill the joints flush with the brick surface, using pointing tools to smooth out excess mortar for a uniform finish. Work in sections and let the mortar set before proceeding to the next.
Finishing and Curing
Once all joints are filled, use a brush to remove loose mortar and refine the surface. Curing is key to durability. Mist the repointed areas with water several times over a few days to prevent drying out and cracking. Don’t repoint in extreme weather conditions like heavy rain, snow, or winter cold, as this can prevent the mortar from setting properly.
Preventing Future Damage
Regular maintenance is key to prolonging the life of your masonry chimney. Schedule an annual chimney inspection to catch small cracks or areas that need repair before they get worse. Applying a breathable waterproofing sealant will help prevent water infiltration without trapping moisture inside. Also, make sure the flue is in good condition and install a chimney cap to prevent weather-related deterioration.
DIY vs. Hiring a Pro
While some homeowners may attempt to repoint a chimney, it’s often best left to the pros. Chimney professionals have the knowledge to assess the damage, choose the right mortar, and make the masonry repairs. Improper repointing can lead to weak joints, more structural issues, and costly future chimney repairs. If the damage is extensive or a full rebuild is needed, hiring a pro is worth it.
Conclusion
Repointing your chimney is a maintenance task that saves the chimney’s structure and prevents house fires from compromising the masonry. By knowing the process, choosing the right materials, and performing regular maintenance, you can prevent fire risk, moisture infiltration, and costly repairs. Hire a GMT Home Services pro; maintaining a strong and weather-tight chimney is key to the life of your fireplace and roof.
FAQs
1. What type of mortar do you use
The type of mortar used depends on the age and material of the chimney. Older brick chimneys need lime-based mortar for flexibility, and newer chimneys need cement-based mortar for durability.
2. What’s the right mix for repointing a chimney?
For older chimneys 1 part lime putty to 3 parts sand is a common mix. For newer chimneys 1 part Portland cement, 1 part lime and 6 parts sand is a stronger bond.
3. What kind of mortar to use?
Type N mortar (cement, lime and sand) is good for general chimney repointing, durable and flexible. Type O mortar (higher lime content) is best for historic or softer brick chimneys.
4. Can you repoint a chimney yourself?
Yes, but repointing is a labor-intensive process that requires skill and the right tools. DIYers must remove old mortar, choose the right mix, and apply new mortar correctly, or risk damaging the brickwork. Hiring a pro will give you long-term results.
