Floor sanding dust is worse. Not by a little, and for reasons that have almost nothing to do with how much of it there is.
Plaster dust is a nuisance that keeps returning for months, and I’ve written a whole article about the return schedule. Sanding dust arrives in one violent afternoon, settles faster, and looks like the easier job. Then you find out what it’s made of, and what the lacquer does afterwards, and which two days of the process nobody warned you about.
A client in Walthamstow asked me last spring which of the two she should be more worried about, because she had a loft conversion finishing and the hall floorboards going back to bare pine the same month. I gave her the short version. This is the long one.
What Makes Sanding Dust Different From Plaster Dust?
Plaster is a mineral. Old pine is not.
Gypsum dust is an irritant — it dries your throat, it hangs about, it settles on everything at the top of a room and comes back down for months. Unpleasant, and at the lower end of the construction dust risk scale.
Wood dust sits in a different category. Hardwood dust is classified as a carcinogen and softwood dust carries its own workplace exposure limit, which is why a floor sander who knows what he’s doing wears a proper mask and extracts at the machine. In a Victorian terrace you’re rarely sanding one clean species anyway. You’re sanding a hundred and thirty years of pine, plus whatever’s been put on it — old varnish, decades of wax, a layer of black bitumen adhesive where lino was stuck down in the fifties, and in a fair few houses the remains of lead paint on the boards nearest the skirting.
That mixture is the reason I treat these jobs differently. It isn’t wood dust, it’s wood dust carrying everything the floor has absorbed since 1890.
The Bitumen and the Lead
Two things that turn a routine sand into something you want off site.
Black bitumen adhesive under old lino goes tacky when a sanding belt heats it, gums the abrasive, and smells like a road being laid. It also means the sander is grinding a petroleum product into airborne particles in your hallway.
Lead paint is the serious one and it’s common on boards, stair treads and skirtings in pre-1970 houses. Sanding it dry is the single worst way to deal with it. If there’s any painted timber in the area being machined, that needs establishing before day one, not discovered by a bloke with a belt sander at half nine on a Monday.
Where Does It End Up, and How Fine Is It?
Everywhere, and finer than the bag suggests.
A drum sander with a dust bag on the back — the standard hire machine — captures a decent share of the coarse material and misses a lot of the fine. Proper trade setups run a separate extraction unit, and the difference in what ends up on your picture rails is dramatic. Ask which one is turning up.
Then there’s the edger, which is the part that does the damage. It’s a handheld machine working the perimeter of every room, under the radiators, into the corners, and it throws fine dust at skirting height straight into the air of the room. Most of the airborne load from a floor job comes off the edger rather than the drum.
In a terrace, that dust goes where the air goes. Up the stairwell, which behaves like a chimney. Into the kitchen through the gap under a closed door. Onto the tops of doors and the curtain headers, same as plaster dust. And into the void under the floorboards you’ve just opened up, where a hundred and thirty years of soot, old horsehair plaster and general filth is waiting to be disturbed.
The Underfloor Void Nobody Mentions
Lift or gap a Victorian floor and you’ve connected the room to a ventilated void with airbricks to the outside and a century of accumulated debris in it.
Every footstep on a newly sanded floor pumps a little of that up through the joints. It’s why some houses feel dusty for weeks after a floor job in a way the sanding alone doesn’t explain, and why I now vacuum the gaps with a crevice tool before anybody thinks about lacquer.
When Is the Dangerous Part, Sanding or Finishing?
Finishing, and this is the bit that catches people.
The sanding is loud, filthy and obvious, so everybody takes it seriously. The lacquer goes on quietly, looks like painting, and the house smells of it for two days. A solvent-based polyurethane releases a substantial load of solvent vapour while it cures, and two coats in a closed terrace with the windows shut against February is a genuinely unpleasant atmosphere to sleep in.
Water-based finishes are better on that front and now perform well enough that I’d specify them for a family home without hesitation. They cost more per litre, they dry faster, and they smell of very little after a day. The old objection was durability and it hasn’t been true for a while.
Either way, the rule is the same. Nobody sleeps in the house during finishing and for a day after. Not the adults, not the baby, not the dog, and particularly not anyone with asthma. That’s the one instruction I repeat until people are annoyed with me.
The Two Days You Can’t Clean
There’s a window after the final coat where cleaning makes things worse, and I’ve watched an eager client ruin a floor with a damp mop on day two.
Lacquer is touch dry in hours and nowhere near cured for a week or more. Walk on it in socks after twenty-four hours if you must. Don’t put rugs or furniture on it, don’t drag anything, and put nothing wet on it for at least a week — water sitting on a green finish leaves a permanent cloudy mark. The floor gets there before you do, and you can’t rush it.
How Do You Clean a Terrace After a Floor Job?
Top down, and the floor genuinely last, which feels backwards to everyone.
Start at the ceiling line — picture rails, cornice, door tops, the top edge of every door frame, curtain poles. Then sills, radiator fins, skirtings. Dust falls, so anything you clean at low level before high level you will be cleaning twice.
Vacuum with a machine that holds what it picks up. A domestic bagless cylinder pushes fine wood dust through the cyclone, loads the filter and blows a share of it back out at head height. Hire an M-class with a sealed bag for the week — thirty to forty pounds a day and it’ll be the best money in the project.
On the floor itself once it’s cured: vacuum with a soft brush head, then a barely damp microfibre mop. Barely damp means wrung until it feels almost dry. Standing water gets into the board joints, swells the timber and lifts the grain, and on a newly sanded pine floor that shows immediately.
No steam mops. No vinegar, no citric solution, nothing acidic — it dulls lacquer and there’s no way back from a dulled floor short of a screen and recoat.
The Stairs, Which Are Always Wrong
Stair treads take the heaviest wear, the edger can’t get into the corners of them, and the risers hold dust on the top edge where nobody looks.
Runner grippers are usually still in the stringers with tacks in them, and the dust packs into that line. A crevice tool, one stair at a time, working down, and check the underside of the nosing where a surprising amount collects.
Should You Be In the House At All While It’s Happening?
For the sanding, you can be, in a sealed-off part of the house with a zip door and taped polythene. For the finishing, no.
Here’s the bit that costs me. Don’t book a professional clean the week the machines leave. A floor job produces a large single deposit that mostly settles within a day or two, so the sensible sequence is that you do a rough pass yourself with a hired vacuum, the decorators finish, and then you book one proper deep clean at the end. One visit, done thoroughly, into the reservoirs — door tops, radiator fins, curtains down, underfloor gaps.
I’d also tell you that the “builder’s clean” offered at the end of a floor quote is usually forty minutes with a broom. It exists to make the handover look finished. Take it off the quote and put the money into a bigger extractor unit on the machine, or into a zip door at the bottom of the stairs, because containment beats cleaning every time and always has.
The client in Walthamstow did both jobs in the same six weeks and the floor was the one that got into everything. She rang in October about a haze on the bannister and I told her it was the loft, still arriving.