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.

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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.

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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.

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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 chatte