When in the schedule
The floor scrub belongs after the last trade that makes dust and before anything that makes the floor hard to reach. In practice that means:
- Drywall finish, paint, and ceiling work are complete.
- Overhead trades are out and their lifts are off the slab.
- The slab has been dry-swept and the piles removed.
- Racking, striping, fixtures, and FF&E have not gone in yet.
If racking install happens after the scrub, expect a second round of grit from the anchors and the forklifts. A lighter re-scrub after racking is common and costs much less than the first pass.
What a scrubber removes, and what it does not
An auto scrubber lifts:
- Drywall and joint-compound dust, including what has been walked into the pores
- Slab grit, sand, and the fine laitance a new floor sheds
- Light mortar and grout haze from tile and masonry work
- Joint-compound drips and small adhesive spots, with the right chemistry
- General residue: footprints, coffee, sawdust film, the gray of a months-old jobsite
A scrubber does not lift:
- Cured flooring adhesive fields
- Heavy mortar or thinset buildup
- Paint fields or heavy overspray
- Curing-compound residue on some slabs
- Anything that needs a surface profile for a coating
Those are mechanical-removal jobs, usually a grinder, and a floor contractor should say so during the walkthrough rather than after a day of trying.
The sequence
1. Walk it with the superintendent
Confirm what is left on the slab, which trades are still coming, where the hose bibs and drains are, and what the punch list says “clean” means. Mark the spots that will need a grinder so nobody expects the scrubber to handle them.
2. Dry pickup
Screws, wire, banding, pallet splinters, and the piles the final sweep left in the corners come up first. A slab that had metal studs cut on it also gets a magnet sweep. Heavy dust is dry-swept, so the wet scrub is left with only the fine dust a broom cannot lift.
3. Full-slab machine scrub
A cleaner suited to the soil is run across the whole floor, including the offices, restrooms, and corners, with extra attention at doors and along the drywall lines where the dust is thickest. The recovery water goes to a sanitary drain, never outside.
4. Haze and spot treatment
Mortar haze, joint-compound drips, and adhesive spots are treated with chemistry made for them. Residue that responds is removed; residue that does not is marked and reported.
5. Rinse pass and dry-down
A clean-water pass leaves no film. The slab is dry within minutes and ready for the next crew, the striping, or the owner’s walkthrough.
6. Photos
Dated before-and-after photos of every bay, the same day, for the closeout package. The owner who was not on site wants to see it, and the tenant who moves in next month wants proof of what they got.
Common mistakes
- Scrubbing too early. A scrub before the painters finish is a scrub you pay for twice.
- Hosing the slab. Water without recovery pushes the dust into the joints and out the dock doors into the storm drain. It also leaves a floor that dries hazy.
- Acid on a new slab. Muriatic acid etches concrete and is not a cleaner. It has no place in a post-construction clean.
- Assuming the scrub preps for coatings. A coating needs the profile a grinder or shot-blaster leaves. A scrub before the coatings crew arrives removes the dust that would otherwise be ground into the slab; it does not replace the prep.
- Skipping the dry pickup. Screws, wire, and dust piles left on the slab add time and cost to the scrub.
- No plan for the water. Recovery water belongs in a sanitary drain. If the building has none connected yet, the plan has to exist before the scrub is scheduled.
What to send a floor contractor for a quote
Square footage, the floor type (bare, sealed, densified, or coated), what trades have been on it, your turnover date, and a few photos of the worst areas. For most shells that is enough to quote from plans; occupied buildings and heavy-residue floors get a walkthrough so the number is right.
How Maddox handles it
Maddox provides post-construction floor cleaning for general contractors, construction managers, and incoming tenants across Greater Houston. Most shells are completed in one to two days, dated photos of every bay are delivered the same day, and a turnover date that moves by a day or two is absorbed without re-quoting.