Cutting concrete safely and precisely is a challenging task. Follow these steps to achieve top-notch results.
Whether you’re cutting concrete blocks, slabs, walls or floors, using the right equipment and techniques will make the job easier, safer and more precise.
Before you get started, these are the tools and materials you'll need to cut concrete safely and successfully.
Recommended tools and materials:
- Diamond masonry blade
- Dust mask
- Drop cloths
- GFCI extension cord when appropriate
- Chalk line
- Gas, electric or air-powered concrete saw
- Wet/dry vacuum
- Mason chisel
- Knee pads
- Face shield
- Steel-toed boots
- Ear protection
- Pry bar
Step 1: Prep your workspace
Begin by analyzing your workspace. Remove any furniture, rugs or other items that could become an obstacle. Cutting a concrete slab in the basement? Drape protective plastic over doorways to contain debris. Turn off and cover any HVAC system to avoid spreading dust. Working outdoors? Dust is less of a concern, but cover any items that could be damaged, and prune back bushes or trees to keep your project area clear.
Step 2: Don protective clothing and eyewear
Using a concrete saw can expose the operator to everything from airborne particulates to flying debris, so wear protective gear when cutting concrete. Recommended protection includes a heavy long-sleeved shirt, pants, steel-toed boots, gloves, face shield, hearing protection and a dust mask. Knee pads and shin protectors will further protect your legs.
Step 3: Time it right
Wet concrete is very difficult to cut, and fully cured concrete can fracture as it’s being cut. So if possible, cut concrete when it’s hard but only half cured. The cut will come out smoother with less dust.
Step 4: Use the best saw for the job
Handheld saws (wet or dry) are good for most concrete cutting applications. Wet vs. dry is partly a matter of personal preference. Wet saws create a messy slurry, but they keep the dust down.
For a large job on the floor, consider using a walk-behind saw. These heavy saws (which are wet) make the straightest and deepest cuts, eliminating the need for repeated shallow cuts. Water keeps the dust down and also keeps those big blades cool.
Whether you go with a handheld saw or walk-behind saw, match the saw to the project. Here are four types of concrete saws to consider.
- Cut-off saw: Available in electric and gas-powered versions, these handheld saws are perfect for cutting concrete, stone and asphalt.
- Air concrete saw: Air-powered handheld saws are low-maintenance and useful for cutting through concrete, reinforced concrete, asphalt, masonry and more.
- Street saws: These concrete saws, which come in walk-behind and handheld models, are ideal for street repairs, utility work, curb cutting and other applications.
- Air walk-behind saw: Best for mid-sized jobs, these saws are pneumatic-powered and feature better handling for work involving concrete, brick and stone.
Step 5: Pick the right blade
In most cases, a diamond saw blade is the way to go. The exposed synthetic diamond crystals on the surface of the blade do the cutting. As the diamonds become dull, they fall away, and new ones are exposed. You can use a dry-cutting diamond blade with or without water. A wet blade must be used with water.
To replace a blade, unplug the saw (or remove the battery) and lay it on a flat surface. Using a wrench, remove the bolt that secures the blade in place. Add the new blade and tighten the nut back into place. To stop the blade from rotating while tightening or untightening, place a screwdriver in the rear hole of the saw.
Step 6: Inspect the saw and saw blade
Using a fully functioning, well maintained saw is a secret to success. Tighten all screws and bolts, make sure the wheel guard is properly mounted and free of cracks, look for missing segments or cracks in the blade’s core, and double-check that the blade is mounted securely. A simple inspection can save you a lot of time and improve the safety and success of your project.
Step 7: Deal appropriately with the dust
Cutting concrete can release minuscule particles of crystalline silica into the air. These particles are small enough to be inhaled deep into the lungs and cause health problems, which is the reason for OSHA’s silica dust rules.If you’re using a dry saw, make sure it has the appropriate dust extractor. (With a wet saw, the dust is washed away before it becomes airborne.)
Step 8: Use the right extension cord for the job
If you’re using an electric saw (as opposed to an air-powered or gas-powered saw), use a GFCI-protected extension cord. GFCI (Ground Fault Circuit Interrupter) devices detect when electric current is leaking and help to prevent electrocution, electric shocks and burns.
Step 9: Mark your cuts
Clearly mark the places you want to cut with a chalk line. Consider using bright orange chalk powder. If you’re using a wet saw and the chalk is washing off, use a crayon.
Step 10: Tape the saw to prevent scratches
Put a strip of duct tape along the bottom of the saw body where it runs against the concrete. This will keep the saw from scratching the concrete surface as you cut.
Step 11: Use a guide board and move the saw forward against it
Secure a straight, smooth board along the outside of the chalk line. Maintain a firm, two-handed grip on the saw and slowly move it forward tightly against the guide board.
If using a handheld saw, make several shallow passes instead of one deep cut. This provides better control of the saw and keeps the blade cooler. After each pass, shut off the saw, then increase the blade depth by ½-inch increments.
Let the saw do the work. All you need to do is guide it in the direction of the cut. Forcing the blade could cause it to overheat. Using the saw’s low RPM setting will also help keep the blade from overheating.
Concrete is definitely hard. But cutting it doesn’t have to be if you know how.
Click here to browse United Rentals’ full inventory of concrete cutting saws and blades.