Walk-Behind Floor Saws (Flat Saws)
Walk-behind saws cut concrete slabs, joints and asphalt with large diamond blades. They create silica dust, run on gas engines that make carbon monoxide, and can hit hidden conduits, post-tension cables and water lines buried in the slab.
- Concrete & cutting
- Road construction
- Plumbers
Silica control
Under OSHA’s construction silica rule (Table 1), walk-behind saws must have an integrated water delivery system that continuously feeds water to the blade, operated as the maker says.
| Where | Respirator under Table 1 |
|---|---|
| Outdoors | None required |
| Indoors or in an enclosed area | APF 10 (like an N95 or half-mask), plus enough ventilation to keep dust from building up |
See Crystalline Silica.
Carbon monoxide kills indoors. Never run a gas-powered saw in a building, garage, basement or trench without strong ventilation and CO monitoring. Use electric, hydraulic or propane saws with proper ventilation for indoor cutting. See Carbon Monoxide.
Before you cut
- Scan the slab (GPR or X-ray) for rebar, conduit, pipes and post-tension tendons
- Call 811 for cuts in outdoor pavement over utilities
- Right diamond blade for the material (cured concrete, green concrete, asphalt) and the saw’s speed
- Blade guard in place, and blade mounted in the right direction
- Water supply hooked up and flowing
- Cut line marked, and the area cordoned off
- Traffic control set up if near traffic
Post-tension cables: Cutting a tensioned tendon can make it explode out of the slab with deadly force. Never cut post-tensioned slabs without a structural engineer’s layout and approval.
While cutting
- Lower the blade slowly into the cut and walk the saw at a steady pace. Don’t force it.
- Cut straight. Turning the saw while the blade is in the cut can bind or break the blade.
- Make deep cuts in passes if the blade or saw calls for it.
- Watch for blade “climbing” out of the cut, and stop if the saw kicks.
- Raise the blade out of the cut before stopping the engine.
- Control the slurry: it’s slippery, and it’s silica-laden waste that shouldn’t go down storm drains.
PPE
- Safety glasses or goggles, hearing protection (these saws are very loud), safety-toe rubber boots, gloves and hi-vis near traffic
- A respirator when required (see the silica table above)
Standards & references
- 29 CFR 1926.1153: Respirable crystalline silica in construction (Table 1)
- OSHA: Silica
- See also: Core Drills · Cut-Off Saws · Concrete Work
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