Concrete finisher screening questions: flatwork, power trowels, ACI certification, timing and curing
On this page
- Which concrete finishing job is it?
- Which certifications and training should a concrete finisher have?
- Knockout questions
- Finishing and timing questions
- Safety questions
- How does concrete finishing experience get overstated?
- Scoring and the note to the superintendent
- Legal cautions
- Questions people ask
Concrete finisher screening questions should establish what the candidate finishes (residential flatwork, commercial slabs on grade, elevated decks, paving, decorative or polished floors), what their job is on a pour, which machines they run (walk-behind and ride-on power trowels, laser screeds, early-entry saws), and how they read timing and weather. The American Concrete Institute's flatwork finisher certifications are voluntary credentials worth asking about, and as of November 2026 OSHA's rules on power trowels, bull floats near power lines, protruding rebar, wet cement and silica dust from saw cutting and grinding shape the safety questions.
General pour helpers who place and vibrate concrete are covered in construction laborer screening questions; form setters in carpenter screening questions; brick and block work and the silica standard in more depth in mason screening questions. When the slab will later take a floor covering, its moisture and flatness also matter to flooring installers.
Which concrete finishing job is it?
| Type | What the work involves | A question that tests it |
|---|---|---|
| Residential flatwork | Driveways, patios, sidewalks, garage slabs; small crews, broom finishes | "How many yards on your biggest residential pour, and what was your job on it?" |
| Commercial slab on grade | Warehouse and retail floors, laser screeds, ride-on trowels, flatness specifications | "What flatness numbers did the spec call for, and how did the crew hit them?" |
| Elevated decks | Slabs on metal deck or post-tensioned decks, pump placement, work near open edges | "How did you work near the deck edge, and who handled the post-tensioning?" |
| Paving, curb and gutter | Public works specifications, hand-formed or slipformed curb, traffic around the work | "What finish and joint spacing did the agency's spec require?" |
| Decorative | Stamped, colored and exposed aggregate concrete | "How do you time the stamps, and what release did you use?" |
| Grinding and polishing | Existing slabs ground, densified and polished | "Which grinder did you run, and how did you control the dust?" |
Which certifications and training should a concrete finisher have?
The Bureau of Labor Statistics covers cement masons and concrete finishers in its masonry workers handbook page: they place and finish concrete, masons often lift heavy materials and stand, kneel and bend for long periods, and the work is mostly outdoors. Unions and contractor associations sponsor apprenticeships, after which workers become journey workers. The national median for cement masons and concrete finishers was $57,020 a year in May 2025. The cement masons' union is the Operative Plasterers' and Cement Masons' International Association; for union candidates, ask which local and when they turned out.
| ACI credential (as of November 2026) | What it takes | What to ask |
|---|---|---|
| Concrete Flatwork Associate | A closed-book written exam of about 50 questions; no experience required | Treat it as knowledge, not proof of finishing. |
| Concrete Flatwork Finisher | A hands-on performance exam (placing, consolidating, finishing, edging, jointing and starting the cure on a slab) plus 1,500 hours of employer-verified finishing | The year, and the card number for verification. |
| Concrete Flatwork Advanced Finisher | The written exam plus either 1,500 hours and the performance exam, or 4,500 hours | Which path they took. |
| Decorative, Specialty Commercial/Industrial, Field Testing Technician Grade I | Separate ACI programs for decorative flatwork, commercial and industrial floors, and slump, air and cylinder testing | Only where the order involves that work. |
ACI's program page says each flatwork level is valid for five years. The full list of programs includes the decorative and testing credentials.
Knockout questions
| Question | What a strong answer sounds like | Red flags |
|---|---|---|
| This order is for [type] finishing. What has most of your work been in the last two years? | A clear split: "Mostly commercial slabs on grade, some sidewalks." | All recent work in a different type. |
| When the first truck arrives, what is your job? | Describes finishing work for an order that asks for a finisher: floating, edging, jointing, troweling. | Only raking and pulling hose, for a finisher order. |
| The client runs [walk-behind / ride-on] trowels. Which have you run, and how recently? | A machine, a site and a month. | "I've seen them used." |
| Pours start at [time] and the day ends when the slab is finished. Can you work those hours, including [Saturdays]? | Yes, and asks how overtime and weather days work. | Needs to leave at a fixed time every day. |
| The work is outdoors and includes kneeling on boards and lifting. Can you do that for the full shift, with or without accommodation? | Yes. | None from the answer. Do not ask medical questions. |
| Do you have your own hand tools and transport to changing sites? | Trowels, edgers, groovers, floats, kneeboards, and a way to get to each site. | No tools, for an order that expects them. |
Finishing and timing questions
-
"Walk me through a slab from the first truck to the end of the day."
- Strong answer: checks forms and grade, places and consolidates, screeds, bull floats, waits for the bleed water to go before more finishing, edges and joints, floats and trowels, applies the finish texture, starts curing.
- Red flags: troweling bleed water into the surface, or sprinkling dry cement or water on the slab to make it easier to finish.
-
"How do you know the slab is ready for the power trowel, and how do you run the passes?"
- Strong answer: tests by stepping on it, starts with pans or float blades, raises the blade pitch a little each pass, and watches the edges and around columns by hand.
- Red flags: goes on at a fixed time regardless of the concrete.
-
"What changes on a hot, windy day? On a cold one?"
- Strong answer: hot: earlier start, wind breaks or shade, an evaporation retarder, curing right away; cold: protected subgrade, blankets, vented heaters, longer protection.
- Red flags: adds water at the truck to make it easier to work, without the supervisor's approval.
-
"Where do the joints go, and when do you cut them?"
- Strong answer: from the drawings, cut as early as the concrete allows with early-entry or conventional saws, to the depth the spec requires.
- Red flags: "Whenever we get back to it," on a slab that cracked.
-
"What flatness did your last floor have to meet, and how was it measured?"
- Strong answer: FF and FL numbers measured under ASTM E1155, or a straightedge tolerance, and what the crew did to hit them.
- Red flags: never knew the floor was measured, for a warehouse order.
-
"How did you cure your last slab, and for how long?"
- Strong answer: curing compound, wet curing or blankets, as the spec called for, and who checked it.
- Red flags: no curing at all.
Safety questions
| Question | What a strong answer sounds like | The rule behind it |
|---|---|---|
| What happens if you let go of the walk-behind trowel? | It shuts off; never blocks the switch. | 1926.702(c): a control switch that shuts off power when the operator's hands leave the handles |
| There are power lines over the slab. What do you check before you bull float? | Clearance, and a handle that is nonconductive or insulated. | 1926.702(h) |
| There is rebar sticking up near your work. What do you do? | Makes sure it is guarded before working around it. | 1926.701(b): guarded to eliminate impalement |
| Concrete went over your boot top. What now? | Stops, washes the skin with clean water, changes socks, tells the foreman; wears waterproof boots tall enough to keep concrete out and butyl or nitrile gloves. | OSHA's portland cement guide on caustic cement burns |
| How do you control dust when you saw joints or grind? | Water fed to the blade or grinding surface, or the dust collection the table allows; a respirator when the employer's plan calls for one. | 1926.1153 Table 1; OSHA's 2019 letter says pouring wet concrete in isolation is likely outside the standard |
| You are finishing near an open deck edge. What do you need? | Guardrails or a tied-off harness before working there. | 1926.501(b)(1): 6 feet or more |
How does concrete finishing experience get overstated?
- Pour laborer as finisher. Raked, pulled hose and vibrated, but never troweled.
- Broom finish as hard trowel. Residential sidewalks presented as warehouse floors.
- Ride-on trowel by proximity. Worked next to the operator. Ask how they set the pitch.
- Decorative from one patio. Ask how many stamped jobs and who timed the stamps.
- Crew yardage as personal output. Ask how many finishers were on the slab.
Scoring and the note to the superintendent
Pass or fail: has done the type of finishing ordered; runs the machines the client uses; can work early starts, long pour days and outdoor conditions, with or without accommodation; has tools and transport.
Scored 0 to 2 each (10 possible):
- Sequence: the slab described in the right order.
- Timing: bleed water, trowel readiness, weather.
- Joints, flatness and curing understood.
- Safety habits: trowel switch, rebar, cement burns, dust.
- Recency and volume of real finishing.
Finisher: [name]
Work type: [residential / commercial slab / decks / paving / decorative / polishing]
Role on recent pours: [finisher / lead / helper], [contractor], [months]
Machines: [walk-behind / ride-on trowel, laser screed, saws]
Certification: [ACI level, number, year / none]
Largest pour described: [yards, crew size]
Candidate's own gap: [e.g. "no stamped work"]Legal cautions
General information as of November 2026, not legal advice. Card, wage and safety rules vary by state and city; confirm them where the site is.
Describe the physical work (kneeling, lifting, heat and cold) and ask whether the candidate can do it, with or without accommodation; do not ask about injuries, skin conditions or workers' compensation history, which the EEOC's pre-employment guidance treats as disability-related before an offer. Machine names, slab types and certification levels blur across a morning of calls; Interview Signal keeps the knockout questions pinned until you ask them and writes the superintendent's note from what each finisher said, with the transcript kept on your own computer.
Questions people ask
What certification can a concrete finisher hold?
The American Concrete Institute offers three flatwork levels: Concrete Flatwork Associate (a written exam), Concrete Flatwork Finisher (a hands-on performance exam plus 1,500 hours of employer-verified finishing experience) and Concrete Flatwork Advanced Finisher (the written exam plus either 1,500 hours and the performance exam or 4,500 hours). Each is valid for five years; ask the client whether its project specifications require one.
Does OSHA's silica standard apply to concrete finishers?
It depends on the task. OSHA's 2019 interpretation letter says pouring concrete, handled wet and done in isolation from other silica tasks, is likely outside the standard. Saw cutting joints and grinding are covered: Table 1 of 29 CFR 1926.1153 lists walk-behind saws, handheld grinders and walk-behind floor grinders with the water or dust controls to use.
What protective gear do concrete finishers need for wet concrete?
OSHA's guide on preventing skin problems from portland cement says wet cement can cause caustic burns that may not hurt at first. It says butyl or nitrile gloves, rather than cotton or leather, are frequently recommended, that waterproof boots must be high enough to keep wet cement out, and that skin should be washed in clean, cool water with a pH-neutral or slightly acidic soap.
How can I tell if a concrete finisher can really run a power trowel?
Ask how they know when the slab is ready, whether they start with pans or blades, how they change the blade pitch between passes, and what the machine's safety switch does. People who have run one describe timing and sequence; people who watched describe the finished floor.