Introduction
Isolation joints separate a slab from vertical or fixed elements, while control joints are intentional shallow cuts that encourage where a slab cracks; put simply, isolation keeps things apart and control tells concrete where to crack. These are different tools for the same problem of movement and cracking, and you choose based on what the slab touches and how you want the crack to behave. For DIYers, know that materials and placement matter—check product labels and local guidance for joint materials and depths.
Isolation joints belong wherever the concrete meets fixed edges like walls, columns, or pipes so the slab can move independently without tearing; control joints belong across the field of the slab to guide shrinkage cracks into neat lines. A practical approach is to plan control joints while the slab is still workable and cut or form isolation joints before the concrete hardens, but check manufacturer instructions and local rules for timing and spacing. When in doubt on spacing, depth, or timing, follow product instructions or ask a pro—better safe than chasing cracks later.
Key takeaways
- Isolation joints relieve movement between slabs and adjoining structures to prevent cracks.
- Control joints guide where cracks form, reducing random cracking across the slab.
- Appropriate placement: isolation joints at transitions, around existing features, and perimeters.
- Spacing guidelines for control joints depend on slab size and drying behavior.
- Use compatible materials; sealants and backer rods follow manufacturer instructions.
- Safety: wear eye protection, watch for trips, and follow local codes.
Table of Contents
- Introduction
- Key takeaways
- Quick Overview: What Isolation and Control Joints Are
- When to Use Isolation Joints (Practical Applications)
- When to Use Control Joints (Timing and Scenarios)
- Placement, Spacing, and Depth Rules for Each Joint Type
- Tools, Materials, and a DIY Checklist
- Step-by-Step How-to for Installing Joints on a DIY Slab
- Repair, Maintenance, and Sealing of Joints
- Safety, Common Mistakes, and Troubleshooting
- Conclusion
- FAQ
Quick Overview: What Isolation and Control Joints Are
Isolation joints (also called expansion joints) are separations placed to allow a slab to move independently from adjacent elements like walls, columns, or different slabs; control (contraction) joints are shallow cuts or formed grooves intended to control where the concrete cracks as it shrinks. Both types manage movement, but they do different jobs: isolation relieves differential movement, control guides shrinkage cracks into neat, predictable lines.
Practically, isolation joints go where the slab meets fixed objects or different substrates, and control joints are laid out across the slab at regular intervals to intercept shrinkage cracks. Installation basics include using proper backer materials and sealants for isolation joints and making control joints to an appropriate depth and width; check the product label or manufacturer data sheet for specific backer rod and sealant compatibility and suggested depths. Timing matters: control joints are cut at the right time during cure to be effective, while isolation joints must be formed before pouring or installed with preformed inserts; if unsure, verify timing instructions with manufacturer guidance or local best practices. Watch for signs of improper jointing—random cracking, spalling at joint edges—and consult a pro for complex or high-load slabs, especially when movement or water intrusion is a concern.
Definition of control joints
Control joints are planned, weakened lines cut into concrete to direct where shrinkage cracks occur. They’re like built-in stress relievers for your slab.
Why use them? Control joints help prevent random cracking by giving the concrete a predetermined path to crack along as it shrinks during curing.
Think of them as the ‘crack control’ system in your DIY slab. They’re especially useful on large, single-pour slabs.
Definition of isolation joints
Isolation joints are separation points between concrete and other materials or pours. They prevent stress transfer and allow independent movement.
Why use them? Isolation joints stop one part of your slab from affecting another, preventing cracks caused by different expansion rates.
You’ll find these at slab-to-slab separations, around fixed objects like pipes or trees, and where slabs meet different substrates like walls or other structures.
How the two interact on a slab
Both control and isolation joints work together to keep your slab in top shape. Here’s how:
Control joints manage internal stresses caused by concrete shrinkage, while isolation joints handle external stresses from different expansion rates.
On a typical DIY slab, you’ll see control joints spaced evenly across the surface (usually 10-24 feet apart), and isolation joints running along edges or around fixed objects. They complement each other to create a strong, durable slab.
When to Use Isolation Joints (Practical Applications)
Use isolation joints whenever a concrete slab abuts a fixed element or a dissimilar material that will move differently than the slab—examples include slab-to-wall interfaces, column bases, junctions with existing slabs, or between separate pours. The purpose is to prevent stresses at those interfaces from causing uncontrolled cracking in the slab by separating and cushioning the concrete from the fixed element.
Layout guidance: place isolation joints at the interface before pouring or install pre-seated inserts so the joint runs full depth of the slab and does not interrupt reinforcement where it must remain continuous; align joints with structural elements and consider work flow to avoid blocking finishers. DIY installation commonly uses compressible joint fillers or preformed gaskets with backer rods and a compatible sealant—check product instructions for appropriate materials and installation sequence. Common mistakes are undersizing the joint, skipping a joint where slabs meet different substrates, or using an incompatible sealant; include a site checklist for expected movement, substrate type, and whether adjacent structures are fixed or moving to decide if an isolation joint is required.
Typical locations (edges, fixed objects, adjacent materials)
Material choices at slab edges and interfaces significantly impact the need for isolation joints. Here are common spots where isolation is crucial:
- Slab-to-wall interfaces: Prevents cracking due to differential movement between slab and wall.
- Column bases: Isolates column loads, preventing stress transfer to the slab.
- Junctions with existing slabs: Minimizes cracking from settlement or expansion of adjacent slabs.
- Edges and corners: Protects edges from spalling due to impact or stress concentration.
- Transitions to different materials: Prevents staining, weak bond, or cracking at material transitions (e.g., concrete to brick).
When you can skip isolation joints
For small residential slabs with minimal movement, isolation joints may not be necessary. However, always check these conditions:
Slab size and movement potential: Small, simple slabs with no significant temperature changes or differential settlement are less likely to require isolation.
Adjacent structures: If there’s no wall, column, or existing slab nearby that could cause differential movement, isolation may not be needed.
Material choices: Using compatible materials with similar expansion and contraction rates reduces the need for isolation.
Visual checkpoints for isolation placement
Before pouring, use this checklist to ensure correct isolation joint setup:
- Gaps at interfaces: Ensure there’s a visible gap (usually 1/4″ – 3/8″) between slab and adjacent materials.
- Backer rod presence: Check for backer rod in gaps to prevent grout from flowing into the joint.
- Material transitions: Verify that isolation material (e.g., foam, rubber) is present at all interfaces.
- Joint width and depth: Measure joints to ensure they meet specified dimensions (usually 1/2″ – 3/4″ wide by 1/4″ – 1/2″ deep).
Quick rule: If in doubt, install isolation. It’s easier and cheaper to add than to fix cracks later.
When to Use Control Joints (Timing and Scenarios)
Control joints are used whenever you need to manage where shrinkage cracks will form in a slab—typical DIY locations include garages, driveways, patios, and basement floors where uniform shrinkage can be expected. Their timing is critical: cutting or forming should occur after the concrete has gained enough strength to hold a clean edge but before uncontrolled cracking begins; consult curing guidance or product instructions for timing windows based on ambient conditions.
Match joint spacing and layout to slab type and environmental drivers—temperature swings, rapid drying, and substrate movement all increase the need for closely spaced control joints and timely cuts. For DIYers, choose between saw-cut joints, grooved joints with a jointer, or preformed inserts depending on tools available and slab size; verify cutting depth guidance with manufacturer recommendations and use appropriate safety gear. Watch for signs of late cuts (random cracking across panels) or cuts too shallow (cracks bypassing the joint) and plan a simple checklist for marking, timing, cutting, and finishing the joint to reduce cracking risk.
Typical slab applications (driveways, patios, interior floors)
Control joints are crucial for most DIY concrete slabs. Here’s why:
Driveways: Vehicles’ weight and temperature changes cause movement. Joints help prevent cracking.
Patios: Furniture, foot traffic, and weathering need jointed slabs to avoid cracks.
Interior floors: Subfloor movement, temperature swings, and moisture can lead to cracks without control joints.
Timing for making control joints
Cutting or forming control joints at the right time is vital:
In early-morning pours, aim to cut by late morning. In late-morning pours, do it before noon.
Why? Concrete starts setting and shrinking soon after pouring. Joints guide these contractions, preventing random cracks.
Hot or windy conditions speed up setting. Cut joints earlier to keep up.
Early-entry methods vs later saw-cutting
Choose your method based on your tools and the slab’s stage:
Grooving/hand tools: Use these for early entry (within 2-4 hours). They’re cheap but may not cut deep enough.
Early-entry saws: These special saws can cut within 6-8 hours, when concrete is still soft. They’re faster than hand tools but pricier.
Conventional saw-cutting: Wait until the slab has hardened (12-24 hours). This method gives clean cuts but requires more waiting time.
Placement, Spacing, and Depth Rules for Each Joint Type
Control joints guide shrinkage cracking and are placed across the slab at regular intervals suited to slab thickness and use; isolation joints separate the slab from fixed elements and must run full depth. A common spacing approach for control joints uses a rule of thumb scaled to slab thickness and use-case, but always confirm spacing guidance against local practice or product recommendations for your situation.
Depth rules: control joints are typically cut to a fraction of the slab thickness to encourage cracking at the joint—follow product and curing guidance for exact depth and timing. Isolation joints should be continuous through the slab thickness and fitted with a suitable filler and sealant; use backer rod when sealing to control sealant depth—check the sealant or backer rod instructions for recommended diameters and installation steps. Avoid placing control joints through fixtures or where reinforcement must remain continuous, and keep isolation joints clear of embedded elements unless detailed in design; run a quick placement checklist (depth, spacing, alignment, sealant compatibility) before work begins.
Control Joint Spacing and Depth Guidelines
Control joints are crucial for managing slab expansion and contraction. They should be cut into your DIY slabs at regular intervals to direct where cracking will occur, preventing random cracks from forming.
Spacing: A common rule of thumb is 8-12 feet apart, but this can vary based on slab thickness and use. For thicker slabs or heavier loads (like driveways), space joints closer together – around 6-8 feet. For thinner slabs or lighter loads (like patios), you can space them further apart – up to 12 feet.
To calculate spacing for non-standard layouts, divide the slab’s length by 8-12 (depending on thickness and use). If the result is a fraction, round down to ensure even spacing.
Depth: Control joints should be cut to about 1/4 to 1/3 of the slab’s thickness. This allows for adequate movement without causing excessive stress at the joint’s surface.
Isolation Joint Sizing and Gap Requirements
Isolation joints separate slabs from fixed objects or dissimilar materials to prevent stress transfer. They should be full-depth, meaning they go all the way through the slab.
Width: Isolation joints are typically wider than control joints – around 1/2 inch to 3/4 inch. This allows for more movement and accommodates sealant and backer rod.
Sealant and Backer Rod: After cutting, fill the joint with a flexible sealant designed for concrete. Before applying sealant, insert a backer rod (a foam or rubber cord) to create a smooth surface and provide extra flexibility.
Isolation joints should be cut after the initial set but before excessive drying to ensure they’re deep enough and maintain their integrity.
Layout Planning and Panel Shape Advice
Proper layout planning helps prevent cracking and ensures even slab expansion. Aim for roughly square panels to distribute stress evenly.
To achieve this, start by dividing your slab area into smaller squares or rectangles. A common size is 8×10 feet, but adjust based on your specific needs. Try to keep panel lengths under 12-15 feet to minimize the risk of long cracks forming.
Avoid placing control joints through fixtures, edges, or reinforcement. Instead, place them along the centerline of panels and around fixed elements like walls or columns. Isolation joints may be needed at perimeter edges where slabs meet dissimilar materials.
Use chalk lines to mark out your layout before pouring concrete. This helps ensure accurate placement of control and isolation joints.
Tools, Materials, and a DIY Checklist
This section focuses on the practical tools and materials a DIYer will need for installing both isolation and control joints, with notes on what to rent versus buy and how joint type affects material choices. Essentials include hand tools (trowels, screeds, jointer/groover), layout tools (measuring tape, chalk line, level), cutting gear (score tool or saw), and safety gear; consult rental houses for heavier equipment if you lack it.
Materials list should cover concrete mix options, joint fillers, backer rods, and sealants; check product data sheets for compatibility and recommended application conditions. Rent heavy-duty saws, power joint cutters, and concrete vibrators when needed, and buy basic hand tools and PPE; verify rental durations and availability before scheduling work. Create a DIY checklist covering pre-inspection, layout, mixing, pour and finish sequence, cutting schedule, sealing steps, and curing—refer to manufacturer guidance for cure times and sealant instructions, and adjust your plan for weather and slab size.
Tools for forming or cutting joints
Before you start, make sure you have the right tools to form and cut your joints. This ensures clean cuts and proper joint depth.
- Grooving tool: Use this for creating control joints while pouring. It’s a must-have for DIYers.
- Walk-behind/hand saw: For cutting isolation joints, use a walk-behind or hand saw to ensure straight cuts.
- Joint cutter: After the concrete has cured, use a joint cutter to finish off any rough edges.
- Hand edger: This tool helps create clean, sharp edges along your slab’s perimeter.
- Tape measure: Measure twice, cut once. Always double-check your measurements before cutting.
- Chalk line: Snap a chalk line to mark out where you’ll be making your cuts.
- Level: Ensure your slab is level before and after cutting joints to prevent cracking.
- Pry bar: Use this to help lift and remove forms after pouring.
Quick rule: Having the right tools makes all the difference in creating professional-looking joints.
Materials: sealants, backer rod, and fillers
Choosing the right materials is crucial for a durable, long-lasting slab. Here’s what you need:
- Joint sealant: Choose a flexible, concrete-compatible sealant like polyurethane or silicone.
- Backer rod: Use this to fill the joint before applying sealant. It comes in various diameters; choose one that fits your joint width.
- Joint filler: For wider joints, use a cement-based filler to help support the slab and prevent cracking.
- Surface sealer: Apply this after sealing joints to protect the entire surface from moisture and stains.
- Curing compound: Use this to keep your slab moist during curing, preventing early drying that can cause cracks.
- Masking tape: Use this to mark off areas where you don’t want sealant or to create straight lines for cutting.
- Form-release agent: Apply this to forms before pouring to ensure they come off cleanly.
Quick rule: Always check compatibility with concrete and finish when choosing materials.
Quick DIY checklist before you pour
Before mixing your concrete, make sure everything is ready to go. This pre-pour checklist helps ensure a smooth process:
- Joint layout: Plan and mark out where all your joints will be using a chalk line.
- Materials on hand: Make sure you have enough concrete mix, sealant, backer rod, and other materials before starting.
- Weather check: Pour when temperatures are between 50-90°F (10-32°C) for best results. Avoid pouring in extreme heat or cold.
- Formwork: Ensure your forms are secure, level, and well-braced before pouring.
- Base preparation: The base should be clean, dry, and compacted to prevent settling and cracking.
- Reinforcement: If using rebar or wire mesh, make sure it’s properly placed before pouring.
- Water source: Have a nearby water source for mixing concrete and keeping the slab moist during curing.
Quick rule: A well-planned pour leads to a successful, durable slab.
Step-by-Step How-to for Installing Joints on a DIY Slab
Begin with site prep and forming isolation joints where the slab meets fixed elements, then place reinforcement and pour the slab following standard finishing procedures; isolation joints should be formed or inserted so they remain full-depth and continuous. Next, set control joint lines based on your layout plan and anticipated shrinkage paths—mark lines before finishing so the schedule is clear to the crew or yourself.
For control joints, choose grooving while the slab is still plastic or saw-cutting after the initial set depending on tools and timing; follow depth and width guidance from the joint method you select and use proper personal protective equipment when cutting. Install backer rod and sealant in isolation joints after allowed cure time per product directions, and clean and prepare control joints before any filler or sealant work. Common checks: verify joint depths, avoid cutting through reinforcement or embedded pipes, and monitor weather to prevent premature drying; if any doubt about timing or methods, check manufacturer instructions or consult a pro.
Step-by-Step Installation Process
Follow this clear, numbered sequence to install joints on your DIY slab efficiently and effectively.
- Preparation: Check weather, gather tools (checklist), ensure slab is ready for jointing.
- Form isolation joints: Place strips, ensure proper depth, protect during pour.
- Set control joint lines: Mark out using control joint spacing and depth guidelines.
- Cut methods: Choose between immediate grooving or later saw-cutting based on slab cure time.
- Finishing steps: Trowel, broom finish, apply sealant if needed, then cure properly.
Installing isolation joints during pour
Setting up isolation strips correctly ensures proper joint function and longevity. Here’s how:
First, place isolation strips along the planned joint lines, ensuring they’re level and at the correct depth.
Protect them during pouring by covering with plastic or cardboard to keep concrete from sticking.
After pouring, remove protective covers once the slab has set slightly. Then, ensure joint material is properly placed before finishing.
Cutting/forming control joints after finishing
Creating control joints at the right time helps prevent random cracking. Here’s how to do it:
For immediate grooving, use a groover tool while the slab is still fresh, following marked lines.
For later saw-cutting, wait until the slab has cured enough (timing guidelines). Use a wet saw with a diamond blade, ensuring a straight line.
Regardless of method, ensure joints run full depth to allow for proper crack control.
Finishing details and cleanup
Proper finishing touches ensure your slab looks great and performs well. Here’s how:
First, smooth edges using a trowel or edger to prevent chipping.
Next, protect joints during the curing process by keeping them moist (cure tips).
Finally, prepare joints for sealant if needed. Clean up tools and materials, then let your slab cure properly before using.
Repair, Maintenance, and Sealing of Joints
Repair and maintenance keep joints functioning and prevent water intrusion or debris buildup; inspect joints periodically for torn sealant, spalling, or evidence of excessive movement. Decide between repair and prevention by looking for signs like gap growth, recurring cracking at joints, or sealant loss—if unsure, check product labels or technical bulletins for acceptable movement ranges and repair methods.
Preparation is key: clean, dry, and remove old sealant and debris before installing backer rod and new sealant, and repair any spalled concrete edges first to provide a sound substrate. Choose a sealant suitable for joint width and expected movement—refer to manufacturer recommendations for temperature limits and primer needs—and follow application and cure instructions exactly. Schedule periodic inspections after seasonal changes, reseal as needed, and use appropriate PPE and ventilation when working with solvent-based products.
Common joint failures and repair methods
Regularly inspect your DIY slab’s joints to catch issues early. Here are common problems and basic repair approaches.
Delamination: When the concrete surface peels off, exposing aggregate. Repair: Remove loose material, clean, and apply a bonding agent before patching with new concrete.
Spalling: Concrete chips or flakes off due to moisture or freeze-thaw cycles. Repair: Remove damaged concrete, clean, and apply a concrete repair product. Reinforce if necessary.
Failed seals: Sealant cracks, peels, or pulls away from the joint. Repair: Remove old sealant, clean, prime, and apply new sealant.
Sealing and resealing recommendations
Seal joints to prevent water intrusion and debris buildup. Here’s when and how:
When to seal: Soon after jointing, or when old sealant fails.
Removing old sealant: Use a utility knife to cut along the joint, then use a sealant remover or heat gun to soften and remove the old sealant.
Selecting compatible sealants: Choose based on joint type (control/isolation), temperature range, and joint width. Follow manufacturer guidelines for best results.
Routine inspection and maintenance schedule
When to use this checklist: Every 6 months or after heavy use/weather events.
- Check seal condition: Inspect for cracks, peeling, or discoloration. Consequences if skipped: Water intrusion, debris buildup.
- Inspect joint movement: Gently push on either side of the joint to check for excessive movement. Consequences if skipped: Joint failure, concrete damage.
- Remove debris: Clean out any dirt or gravel from joints using a wire brush or compressed air.
- Check for water leakage: Inspect around the joint and below it for signs of moisture. Consequences if skipped: Concrete deterioration, mold growth.
- Inspect backer rod: Ensure it’s still in place and not damaged. Consequences if skipped: Inadequate sealing, water intrusion.
- Check joint width: Ensure it hasn’t narrowed or widened excessively. Consequences if skipped: Ineffective sealing, concrete damage.
- Inspect edges: Check for chipping, spalling, or other damage at joint edges.
- Check temperature range: Ensure sealant is still within its recommended temperature range. Consequences if skipped: Sealant failure due to extreme temperatures.
Quick rule: If in doubt, reseal or repair. Better safe than sorry!
Safety, Common Mistakes, and Troubleshooting
Safety starts with the right PPE—gloves, eye and ear protection, and a respirator when cutting or applying solvent-based sealants—and extends to dust control, electrical safety for power tools, and stable slab access during work. Plan wet or dry cutting methods based on blade and tool recommendations and ensure proper ventilation and dust suppression to protect yourself and bystanders.
Common DIY mistakes include confusing isolation and control joints, incorrect spacing or depth, and cutting too early or too late; these errors lead to random cracking, spalled joint edges, or ineffective seals. Troubleshoot by assessing crack patterns to determine if they are shrinkage, settlement, or joint failure; re-cutting, widening, or resealing may be needed—check product guidance for compatible fillers and when to involve a professional for structural concerns. Keep a maintenance schedule and recheck joints after major weather events or seasonal shifts to catch problems early.
Safety precautions and PPE
Working with concrete requires proper safety measures. Start by wearing the right protective gear:
- Gloves: Protect your hands from cuts, abrasions, and chemicals.
- Eye protection: Wear safety glasses or goggles to shield your eyes from debris and splashes.
- Ear protection: Use earplugs or earmuffs when using power tools like saws.
- Respirator: If you’re cutting or grinding, wear a respirator to protect against dust and fumes.
Always ensure proper ventilation when cutting or sealing joints. Keep the work area clean and free of tripping hazards. Be cautious around fresh concrete; it can be slippery and may not support your weight yet.
Common DIY mistakes and how to avoid them
Even with the best intentions, DIYers often make common mistakes. Here are some to watch out for:
- Incorrect joint type: Ensure you’re using isolation joints where needed (around fixed elements) and control joints elsewhere.
- Improper spacing or depth: Follow recommended spacing and cut joints deep enough – about 1/4 to 3/8 of the slab’s thickness.
- Cutting too late/too early: Timing is crucial. Cut control joints when the concrete has set but isn’t fully hardened (around 20-30% hydration).
- Leaving debris in the joint: Clean out all loose material after cutting to prevent weak points.
- Failing to clean and dry the joint before fill: Ensure joints are clean, dry, and free of contaminants for proper adhesion of sealants or fillers.
Avoid these pitfalls by following our guidelines and taking your time. It’s better to do it right once than to have to repair mistakes later.
Troubleshooting unexpected cracking or movement
Cracks in your slab aren’t always cause for alarm, but they should be investigated. Here’s how to diagnose the issue:
- Shrinkage cracks: These are usually hairline and random. They appear as the concrete dries and shrinks.
- Settlement cracks: These are wider, diagonal, or step-cracking patterns. They indicate uneven settling of the slab.
- Joint failure: Cracks along joint lines may indicate inadequate spacing, depth, or timing of joints.
If you find settlement issues, consider re-compacting the base or adding more reinforcement. If cracks are due to joint placement, re-cut or widen joints as needed. Always use compatible fillers or sealants for repairs.
Conclusion
In the end, getting isolation and control joints right protects your slab from cracks, reduces repair costs, and keeps the surface looking clean and level. Safety and careful placement now prevent big headaches later.
Make it work by following a simple flow: verify where isolation joints are needed, confirm timing for control joints, measure spacing and depth to match the rules you’ve learned, gather the listed tools and materials, install or repair in a dry, clean area, seal properly, test a small section first, and then treat the rest with steady, deliberate work. Start with a dry run, mark your joints, then cut or install with steady hands, and finish by sealing and checking for gaps or movement.
Common mistakes to avoid include skipping the isolation joint where it’s needed, overloading joints with wrong materials, or rushing the cut depth and leaving uneven surfaces. Always wear proper eye and hand protection, keep joints clean while you work, and test a small area first to catch issues before they spread. If something feels uncertain or you’re dealing with a large slab, pause and reassess rather than forcing a questionable fix.
If the slab is unusually large, has complex joints, or you’re unsure about load conditions, it makes sense to bring in a professional. When in doubt, err on the side of conservative spacing and proper sealing, and keep the project moving with clear, measured steps. Stay disciplined, stay safe, and you’ll finish with a durable, professional-looking result.
FAQ
What’s the difference between isolation joints and control joints?
Isolation joints separate slabs from other structures and allow movement without tearing the slab. Control joints are grooves or cuts in a slab that guide where cracks will form, keeping cracks from random places.
What’s the purpose of each joint type on a DIY slab?
Isolation joints protect edges and connected structures from shifting, while control joints manage expected concrete movement by creating pre-planned cracking points.
Where should you place control joints in a DIY slab, and how do you space them?
Place control joints along lines where movement is likely and at regular intervals based on slab size and thickness. For DIY projects, follow the manufacturer instructions for spacing and depth, and keep joints continuous through the slab if possible.
What materials do you need for isolating and controlling joints, and what should you buy?
You’ll need joint fillers or sleeves, sealants compatible with concrete, and proper sawing or routing tools. Check labels and datasheets for compatibility with your slab and climate, and source products that match your joint type and expected movement.
How do you maintain and seal joints to keep them functioning long-term?
Keep joints clean and free of debris, reseal as the sealant wears, and repair any cracks that deviate from the joint line. Use products within their service life and follow manufacturer instructions for re-coating or replacing sealants.