Raking out brick joints safely: depth targets and avoiding chipped arrises

Old mortar removal is typically driven by deterioration, water ingress, or the need for aesthetic renewal. Raking fits into a larger repointing plan or routine maintenance rather than a one-off fix. It also serves inspection goals by exposing the backing for assessment.

Use clear decision criteria to decide if raking is needed. Consider joint depth, brick condition, salt efflorescence, and any movement or cracking that signals deeper work. Compare this with surface re-tuck or cleaning when the backing remains solid and damage is superficial.

Identify Mortar Damage in Brickwork Joints

Inspect your brickwork for visible signs of mortar deterioration or failure. These include:

• Loose or missing mortar: If a screwdriver easily crumbles the joints when poked, the mortar needs to be raked out.
• Deep shrinkage cracks: Cracks wider than 1/8 inch (3 mm) or running deep into the joint indicate mortar failure and require removal.
• Recurring damp patches: Persistent moisture in joints can cause further damage. If you notice dampness, rake out the affected areas.
• Crumbly joints: When the mortar crumbles easily when touched, it has lost its bond and needs to be removed.

Risks of delaying or doing it incorrectly

Delaying necessary mortar removal or performing the task incorrectly can lead to serious consequences:

Accelerated water penetration: Old, damaged mortar allows water to enter more easily, leading to further damage and potential structural issues.

Brick movement: When mortar fails, bricks can shift, causing cracks in the wall and potentially weakening its overall structure.

Frozen-wall damage: Water that penetrates due to failed mortar can freeze and thaw, causing further damage to both the mortar and the bricks themselves.

Higher future repair costs: Promptly addressing mortar issues prevents them from becoming larger, more expensive problems down the line.

Back to top ↑

Essential hand tools include a joint raker or slick, a pointing trowel, a stiff-bristle brush, and a trowel for cleanups. Power options cover an angle grinder with a diamond wheel, an oscillating tool with a scraper, and a rotary hammer for larger sections. Gather these with appropriate PPE and containment gear.

Prep supplies include brushes, a bucket, a chisel or grout saw, a vacuum, and damp rags. Repointing materials should match the brick era, with lime-based or cement-based options as appropriate. Consider color matching and any bonding agents or plasticizers as needed.

Raking Tools (Hand and Power)

Selecting the right tools for raking out brick joints is crucial for efficient and safe work. Here are some essential hand and power tools to consider:

• Pointing Chisel: A versatile tool for removing old mortar, offering precise control. Tip: Use a chisel with a sharp edge to minimize damage to bricks.
• Bolsters or Tuckpointing Tools: Ideal for working in narrow joints and reaching tight spaces. Tip: These tools allow for better control when dealing with delicate or intricate joints.
• Angle Grinder with Diamond Blade: A powerful tool for removing large amounts of mortar quickly. Warning: Use caution to avoid damaging bricks; keep the blade perpendicular to the wall.
• Oscillating Multi-Tool with Raking Blade: Suitable for medium-sized jobs, offering good control and reduced dust. Tip: Opt for a tool with variable speed settings to adjust power as needed.
• Rotary Hammer: A heavy-duty option for removing large sections of mortar or hard cement-based mortars. Warning: Use with care to avoid damaging bricks; secure the wall if necessary.

Personal Protective Equipment (PPE)

Proper PPE is essential for minimizing health risks and ensuring safety during joint raking. Here are the key pieces of PPE to wear:

• Eye Protection: Safety glasses or goggles protect eyes from debris and dust. Tip: Choose eye protection that fits well and provides adequate coverage.
• Respiratory Protection (Silica/Dust Rated): A respirator or dust mask protects against silica dust and other harmful particles. Tip: Use a respirator rated for silica/dust to ensure proper protection.
• Hearing Protection: Earplugs or earmuffs safeguard hearing from power tool noise. Warning: Use hearing protection when working with tools that emit noise levels above 85 dB(A).
• Gloves: Protect hands from cuts, irritants, and harmful substances. Tip: Choose gloves that fit well and provide adequate grip.

Repointing Materials to Have On Hand

The right repointing materials ensure a strong, durable, and aesthetically pleasing repair. Here are the essential materials to have on hand:

• Matching Mortar: Use a mortar mix that matches the existing mortar in color, texture, and composition. Tip: For historic masonry, use lime-based mortars; for modern masonry, use cement-based mortars.
• Backing Rod or Sand: Maintain joint width by using a backing rod or filling with sand before applying new mortar. Warning: Incorrect joint width can lead to cracking and weak bond.
• Pointing Trowels: Essential for applying and shaping new mortar. Tip: Choose trowels with sharp edges for better control.
• Brushes: Clean joints and remove excess mortar. Tip: Use stiff-bristle brushes for better cleaning.
• Softeners (Optional): Add softeners to match the finish of existing mortar. Tip: Consult manufacturer instructions for proper usage and mixing ratios.

Back to top ↑

Common mortar types include lime-putty, lime-putty with Portland cement, and traditional Portland cement-lime mixes. Note properties such as porosity, hardness, set time, and moisture handling. These factors guide safe raking depth and select a suitable repointing approach.

Compatibility with the substrate matters to prevent suction, damp damage, or stress at joints. Softer lime mortars require gentler removal, while harder cementitious mortars may tolerate deeper raking but risk exposing brick surface if done aggressively.

Common mortar classes and characteristics

Mortars used in brick masonry can be broadly classified into two types: lime-rich and cement-rich. Lime-rich mortars, often referred to as traditional or historic mortars, are made primarily from natural hydraulic limes and sand. They are softer, more breathable, and better suited for older, porous bricks.

Cement-rich mortars, on the other hand, contain a higher proportion of Portland cement, making them harder, less permeable, and more suitable for modern brickwork with lower porosity. However, they can be too rigid for historic structures, leading to cracking over time.

Key differences between these classes include:

• Hardness: Lime-rich mortars are softer, cement-rich are harder.
• Breathability: Lime-rich mortars allow moisture to pass through more easily, while cement-rich mortars can trap moisture.
• Suitability: Lime-rich mortars are better for historic brickwork, while cement-rich mortars are suitable for modern bricks.

How to check compatibility before repointing

Before repointing, it’s crucial to ensure the new mortar is compatible with your existing brickwork. This involves checking color, texture, and strength to match the original.

First, perform a simple scratch test: Scrape a small amount of the old mortar onto a hard surface. If it crumbles easily, it’s likely a soft lime-based mortar. If it maintains its shape, it may be cement-based or have a higher cement content.

Next, consider taking mortar samples for lab analysis or specialist review. This can provide detailed information about the mortar’s composition and properties. When in doubt, consult a mason or conservator to help determine the best course of action.

Back to top ↑

Safe depth targets aim to remove the deteriorated outer portion while preserving sound backing. Do not remove so deeply that brick faces become exposed or distress appears. A practical limit should be established and checked as work progresses.

Back the assessment with a backing check: ensure the masonry backing remains solid and free of powder or crumbling areas. If backing shows issues, reassess depth or seek professional assessment before continuing.

General depth guidelines and safe ranges

The primary goal of raking out brick joints is to remove deteriorated mortar while preserving sound masonry. Aim to take out most of the damaged material, typically around two-thirds of the mortar depth, down to clean, sound backing.

It’s crucial not to overdo it. Raking too deep can expose bricks or weaken the joint, leading to further damage. As a practical limit, do not remove more than about half the original joint depth.

Stop immediately if you encounter exposed bricks, distressed masonry, or powdery backing during removal. These are signs that you’ve gone too deep or that the masonry is unstable and needs further assessment or stabilization.

Differences for vertical (perpends) vs horizontal (beds) joints

Horizontal bed joints and vertical perpend joints serve different functions in masonry construction. Horizontal joints, or beds, support the weight of the wall above, while vertical joints, or perpends, help tie the wall together laterally.

When deciding how deep to rake out, consider these differences:

Beds may require more careful attention as they play a critical role in maintaining structural integrity. If both types of joints need work, prioritize beds over perpends. However, always inspect and address any severely deteriorated beds first to prevent further weakening.

Differentiate hand-tool and power-tool approaches, choosing based on joint condition and risk to edges. Both should emphasize controlled, shallow passes to avoid edge damage. Maintain consistent speed and avoid deep plunges near corners.

Protect edges with bracing, shields, and proper scaffold or ladder setup. Set up depth gauges and use sharp rakes or blades to minimize chatter. Follow a step-by-step workflow from assessment to measured passes, stopping to reassess edge integrity as needed.

Hand-tool technique essentials

Mastering hand-tool techniques for raking out brick joints ensures minimal damage to arrises. Follow these safe chiseling tactics:

• Use light taps: Gently tap the chisel with a hammer, avoiding heavy blows that could chip edges.
• Work from the middle outward: Start chiseling from the center of the joint and work your way towards the edges to avoid levering against arrises.
• Keep tools sharp: Regularly sharpen and maintain your chisels to ensure clean cuts. Dull tools can cause damage and require more force.
• Avoid levering against brick arrises: Be mindful of how you’re holding the tool; avoid using it as a lever that could press against and potentially chip edges.
• Use optional tools: Consider renting or borrowing specialized chisels designed for masonry work, which may offer better control and reduced risk of damage. Always check tool condition before use.

Power-tool technique and blade selection

Proper power-tool techniques and appropriate blade selection are crucial for preventing brick edge nibbling during raking out. Follow these guidelines:

• Select blades/discs suited for mortar: Choose blades or discs specifically designed for masonry work, as they have teeth optimized for cutting through mortar.
• Use low speed and shallow cuts: Set your tool to a low speed setting and make shallow passes to avoid aggressive cutting near edges. Consult your tool’s manual for recommended speeds.
• Hold the tool steady: Maintain a firm, controlled grip on the tool to minimize vibrations and prevent skipping or binding that could damage edges.
• Remove small amounts at a time: Take incremental bites out of the mortar joint to avoid nibbling the brick edge. Work in short sections, reassessing edge integrity as you go.
• Consider optional tools: Rent or borrow specialized power tools designed for masonry work, which may offer better control and reduced risk of damage. Always check tool condition before use.

Edge-protection and sacrificial methods

Protecting brick arrises from accidental contact during raking out is essential for preserving their integrity. Implement these edge-protection strategies:

Use temporary guards: Apply timber strips, masking tape, or soft pads to shield arrises from accidental tool contact. Regularly inspect and replace or reinforce edge protection as needed.

Work in short sections: Rake out small areas at a time, allowing you to monitor and protect edges closely. This approach also helps maintain control over your tools and reduces the risk of damage.

Reassess technique if arrises show signs of damage: If you notice any chipping or other signs of damage, stop work immediately and reassess your technique. Consider switching to hand tools for delicate areas to minimize further damage.

Back to top ↑

Prevent chips by keeping tool angles gentle and removal gradual, with consistent depth control. Work methodically to avoid contact with protruding arrises. Mask adjacent surfaces to protect finishes.

For small chips, use color-matched epoxy or repair mortar and feather edges. Finish with a compatible sealant or lime wash if appropriate. Reserve replacement when chips exceed defined limits or threaten structural integrity.

Quick Onsite Repairs for Small Chips

For minor cosmetic damage, quick onsite repairs can be effective. First, assess the chip size and depth. If it’s small (<1/4 brick height) and shallow (not affecting the bond line), proceed with these steps:

Use a color-matched repair mortar or lime putty to fill the chip. Ensure you feather the edges smoothly to blend the repair with the surrounding brickwork. Apply the material using a trowel, then smooth it out with a damp sponge.

Common mistakes include not matching the color correctly or applying too much pressure, which can cause further damage. If your repair doesn’t blend or causes more damage, consider seeking professional help.

When to Replace a Brick or Stop the Job

Knowing when to replace a brick or seek professional help is crucial for maintaining your wall’s structural integrity and long-term performance. Evaluate if the repair can restore the mortar bond line and weather resistance. If not, consider replacing the brick.

Inspect the damage. If you find large spalls (>1/4 brick height), compromised arrises affecting bonding, or widespread damage, it’s time to replace the brick. However, if there are signs of structural concerns or extensive damage, stop work immediately and consult a professional. It’s better to err on the side of caution than risk further damage.

Common mistakes include attempting to repair severe damage without proper assessment or continuing with repairs when structural integrity is compromised. Always prioritize safety and structural soundness over cosmetic fixes.

Back to top ↑

Prioritize dust control with wet cutting, local exhaust, and appropriate PPE. Establish containment to prevent spread of debris. Plan for safe disposal of waste materials.

Assess potential hazards in old mortar, including lead, PCBs, or asbestos, and arrange certified testing if needed. Follow regulatory requirements for ventilation, permits, and site protections when working in occupied or historic buildings.

Dust, Silica, and Hazardous-Material Precautions

Choosing the right methods to control dust and protect against hazardous materials is crucial for a safe brick joint raking process.

• Respirators: Use NIOSH-certified respirators with P100 filters or higher to protect against silica dust and potential hazardous materials. Ensure the respirator fits properly and maintain it according to manufacturer instructions.
• Wet cutting: For high dust-generating tasks, use wet cutting methods to dampen the material and reduce dust. This can be done using a water-fed diamond blade or by applying water directly to the cutting area.
• Local exhaust ventilation (LEV): Use LEV systems with HEPA filters to capture and contain dust at the source. Ensure the system is properly maintained and used according to manufacturer guidelines.
• Isolation: Isolate work areas using plastic sheeting or other barriers to prevent dust from spreading to other parts of the building or affecting nearby workers. Regularly clean isolated areas to maintain a safe working environment.
• Pre-testing for hazardous materials: Before starting work, test old mortar for the presence of lead, asbestos, and PCBs using a certified laboratory. This will help determine the appropriate PPE and work procedures required to ensure safety.

Safe Working Practices and Scaffolding Considerations

Establishing a stable working platform is essential for safe and efficient brick joint raking. Follow these guidelines to ensure your safety and the integrity of the masonry.

Minimize vibration transfer: Use appropriate scaffolding systems that minimize vibration transfer to the masonry. This helps prevent damage to the bricks and mortar, ensuring a strong bond when repointing.

Edge protection: Install edge protection on all open edges of the scaffold to prevent falls. Ensure the edge protection is securely fastened and complies with local regulations.

Avoid overloaded or unsupported bays: Do not overload scaffolds beyond their maximum load capacity, and ensure that all bays are properly supported. Overloading or leaving bays unsupported can lead to scaffold collapse, causing serious injury or death.

Back to top ↑

Weigh immediate savings from DIY against the cost of specialized tools, rentals, protective gear, and potential rework. Factor in time and the possibility of hidden repairs that may be required later. Consider opportunity costs as part of the decision.

When deciding to hire a professional, evaluate extent of damage, accessibility, weather windows, and whether precision is required to preserve aesthetics. Request certifications, warranties, and documented examples from chosen contractors to ensure future maintenance compatibility.

Typical consequences of improper raking and repointing

Improperly executed brick joint raking and repointing can lead to several long-term issues that compromise the structural integrity and longevity of your building. Trapped moisture in widened or uneven joints can accelerate brick erosion, leading to further damage over time.

Incompatible mortar mixes can cause cracks around distressed bricks due to differential expansion and contraction. These cracks allow water intrusion, exacerbating the problem and potentially leading to higher repair costs later on.

Regular tactile examinations of your brickwork can help detect soft or crumbling mortar early, allowing for prompt repointing, repair, or replacement as needed. Additionally, regular visual inspections can help identify signs of damage before they become major issues.

When to consult or hire a mason or conservation specialist

While DIY raking and repointing can save you money, there are situations where it’s crucial to consult or hire a professional. Structural cracks or widespread failing mortar indicate significant damage that may require the expertise of a mason.

If your building is listed or historic, or if you need to match historic mortar, consider hiring a conservation specialist. They have the specialized knowledge and experience needed to preserve the character and integrity of older buildings.

Before hiring, always check professional certifications and ask for references from previous clients. Documenting the project also helps with future maintenance and reference. It’s essential to ensure you’re getting quality work that will last.

Back to top ↑