A brick chimney is a classic architectural feature that adds beauty and character to many homes. However, exposure to the elements can cause wear and tear over time. Cracks, crumbling mortar, missing bricks, and other damage may occur, potentially creating safety hazards and reducing the chimney’s functionality. Thankfully, most brick chimney issues can be repaired with the right techniques and materials. This comprehensive guide will teach you everything you need to know to properly repair a brick chimney yourself.
Assessing the Damage
The first step is thoroughly inspecting the chimney to identify all areas needing repair. Look for:
- Cracks or missing/damaged bricks – Cracks wider than 1⁄4 inch require repointing. Missing or cracked bricks need replacement.
- Deteriorating or missing mortar joints – Mortar keeps bricks bonded together. Old or missing mortar allows moisture intrusion, damages bricks, and decreases structural integrity.
- Leaning or bulging sections – Indicates the chimney is pulling away from the house. Could require rebuilding sections.
- Rust stains or damaged concrete caps – Suggests water is penetrating the chimney. The cap may need replacing.
- Loose bricks sounding hollow when tapped – Signifies damaged or deteriorating interior flue liners.
- Plants, moss, or debris growth – Can accelerate mortar/brick damage and indicates moisture issues.
Carefully inspect all sides from ground level and higher vantage points with binoculars. Look for the above issues and identify every spot needing repair for planning your project.
Gather the Right Materials
Repairing a brick chimney requires specialized masonry supplies and tools. Gather the following before starting:
Mortar
- Premixed tuckpointing mortar – For repointing mortar joints
- Mortar mix or refractory cement – For larger repairs
Match color and texture to existing mortar.
Bricks
- Clay bricks matching existing size and color
- Concrete corner quoins for reinforcing corners
Masonry Tools
- Tuckpointing trowels – For applying mortar
- Pointing or jointing tools – For finishing mortar
- Mason’s hammers and chisels – Removing old mortar
- Grout bags – Filling joints
- Whisk brooms – Brush away debris
Other Supplies
- Masonry water repellent sealant
- Plastic sheeting/tarps
- Shop vacuum
- Safety equipment – Gloves, goggles, mask, hard hat
Repointing Mortar Joints
Tuckpointing repairs eroded or cracked mortar between bricks. Follow these steps:
- Chisel out damaged mortar – Use a masonry chisel and hammer. Remove mortar to a depth of at least 1⁄2 inch. Sweep away debris.
- Wet bricks – Use a garden hose or spray bottle. Lightly dampen repair areas to prevent mortar from drying too rapidly.
- Apply new mortar – Load tuckpointing trowel and pack fresh mortar deeply into joints. Overfill slightly.
- Tool joints – Shape new mortar using a jointing tool to match original appearance. Create concave mortar joints for optimal water runoff.
- Brush and moist cure – Lightly brush loose mortar particles. Mist with water and keep moist for 72 hours for proper curing.
Repoint all cracks and sections where mortar is missing, crumbling, or powdery. Take time to match original mortar color/texture. Proper repointing strengthens structural integrity and prevents water intrusion.
Replacing Damaged Bricks
Cracked, spalled, or missing bricks must be replaced to restore structural stability and appearance. Follow these steps:
- Remove damaged bricks – Use a masonry chisel and hammer to carefully chip out old bricks. Remove all loose material.
- Prep area – Remove additional mortar as needed to expose surrounding brick edges. Vacuum debris. Dampen repair area.
- Dry fit new bricks – Test fit replacement bricks without mortar. Ensure proper fit and alignment.
- Apply mortar – Butter contact surfaces of replacement bricks with mortar. Use enough to fill joints and create a strong bond.
- Set new bricks – Press bricks firmly into place, squeezing out excess mortar. Tap with hammer if needed.
- Tool joints – Shape joints between new and existing bricks with a jointing tool. Match original appearance.
- Clean and cure – Brush away excess mortar. Mist area and keep moist for 72 hours.
Take care removing damaged bricks to avoid cracking/damaging surrounding ones. Test fitting new bricks ensures a proper fit before mortaring in place.
Rebuilding Sections or Chimney Crown
Severely damaged sections may need rebuilding, using these steps:
- Support chimney – Erect plywood/timber bracing to support chimney before rebuilding damaged sections.
- Remove bricks – Number each brick’s position, then carefully dismantle damaged section. Salvage intact bricks.
- Clean surface – Use a chisel, wire brush, and shop vacuum to remove old mortar and debris from exposed surface.
- Construct formwork – Erect non-collapsing forms around damaged section to hold bricks/mortar as rebuilding.
- Install reinforcement – Use steel rebar, anchors, or metal lath inside forms to reinforce rebuilt section.
- Lay firebricks – For chimney liner, install new firebricks if needed, using refractory cement.
- Lay bricks – Butter bricks with mortar and lay new bricks, salvaged or replacement, in original pattern.
- Fill formwork – Pack mortar between bricks and around outside, filling formwork cavity as laying bricks.
- Remove forms – Once mortar cures, carefully remove support forms.
- Finish joints – Repoint mortar joints and finish to match existing chimney.
For damaged chimney tops/crowns, rebuild using concrete or masonry materials. Apply waterproofing sealant when complete.
Applying Water Repellent Sealant
Water penetration accelerates chimney damage from repeated freeze-thaw cycles. Applying a silicone-based masonry water repellent sealant helps protect repaired areas. Follow product directions to roll or brush sealant over repaired sections and mortar joints. This creates a protective barrier. Reapply sealant every few years for optimal results. Proper sealing is key to preventing recurring damage.
Hiring a Professional Mason
For homeowners uncomfortable performing chimney repairs themselves, hire a professional mason. They have specialized expertise and equipment to safely access and repair chimneys. Get multiple estimates and check references to select a qualified mason. Be sure the mason thoroughly inspects the chimney and addresses all necessary repairs. Agree on a written contract detailing repair scope and costs before work begins.
Safety Precautions
- Wear safety goggles, mask, gloves, hard hat when repairing chimneys. Falling debris is dangerous.
- Erect fall protection barriers like plywood shelters or catch platforms when working at heights.
- Use scaffolding or lifts for access. Never lean ladders against chimneys.
- Carefully remove/dismantle collapsed or damaged sections to avoid sudden structural failures.
Preventing Future Damage
Proper chimney maintenance helps minimize repairs:
- Have chimney inspected and cleaned annually by a certified chimney sweep.
- Reapply water repellent treatments every few years.
- Check flashings and repair any leaks immediately.
- Ensure rain caps and spark arrestors are secure.
- Keep trees and plants trimmed back from chimney.
- Check for animals, birds, insects blocking flue – chimney caps deter this.
With the right methods and materials, repairing a brick chimney is very doable. follow safety precautions and take time to properly inspect, prep, execute, and cure all repairs for long-lasting results. Then implement preventive maintenance to protect your chimney’s beauty and function for years to come.
Frequently Asked Questions About Repairing Brick Chimneys
Here are answers to some commonly asked questions about repairing brick chimneys:
What kinds of mortar should I use when repointing or repairing my chimney?
For repointing mortar joints, use a pre-mixed tuckpointing mortar that matches the color and texture of your existing mortar as closely as possible. For larger repairs, use a standard mortar mix or refractory cement designed for chimney applications.
How can I match old mortar color when repointing?
Matching existing mortar color and texture can be tricky. Take a small sandpaper cleaned sample of the old mortar to your local building supply store. They can do color matching and recommend a suitable pre-mixed tuckpointing mortar.
Should I use brick sealant or water repellent on my chimney?
Yes, applying a silicone-based masonry water repellent sealant after repairs is highly recommended. This creates a protective barrier against water penetration that can damage repaired areas. Reapply sealant every few years.
How do I safely access my chimney for inspection and repairs?
Use scaffolding or lifts properly secured and placed on stable, level ground. Position safely away from electrical lines. Never lean ladders against chimneys. For multi-story heights, hire professional chimney repair contractors with proper equipment.
How do I find replacement bricks matching my existing chimney bricks?
Check with local brick suppliers to source replacement bricks that closely match the size, color, and texture of your existing bricks. Or, carefully salvage intact bricks from less visible areas of your chimney during repairs.
What causes leaning or bulging in brick chimneys?
This type of damage is typically caused by inadequate foundation support as the chimney settles, or by weak points allowing the chimney to pull away from the house. Usually requires rebuilding affected sections and reinforcing with rebar, anchors, or lath.
Why is my repaired chimney leaking again after repointing the bricks?
Insufficient surface prep or mortar joint depth when repointing can lead to persisting leaks. Joints may need re-repointing for proper sealing. Also apply water repellent sealant after repairs. Keep chimney crown in good repair.
Should I rebuild a damaged chimney section myself or hire a professional?
It depends on your skill level. Severe chimney damage like collapsed sections often requires professional expertise and equipment for proper rebuilding. But minor to moderate repairs can often be DIY if you use appropriate caution.
Conclusion
Repairing a brick chimney involves assessing damage, gathering the right masonry materials and tools, repointing mortar joints, replacing bricks, rebuilding sections, applying water repellent sealant, and proper maintenance. Follow safety precautions when working at heights. Take time to properly inspect, execute, and cure all repairs. Hire professional chimney masons if needed, especially for extensive rebuilding projects or multi-story heights. With the right approach, homeowners can successfully repair many brick chimney issues themselves and preserve the functionality and aesthetic appeal of this classic architectural feature.