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Drywall Sanding and Dust Control: Vacuum Sanders, Poly Walls, Negative Air, the Furnace Filter, and the Test Before You Sand Anything Built Before 1990
Drywall, Taping & Painting
Sanding and Dust: How the Professionals Keep It Out of Your Furnace, Your Lungs and Your Sock Drawer, and the One Case Where You Do Not Sand at All
Drywall dust is the finest dust in construction. It goes through a furnace filter, it gets into closed drawers, and it shows up in the basement a week after the taper left the second floor. In a new house it is a nuisance; in a house with a family in it, it is the thing the family remembers about the renovation. It is also, in a house built before 1990, possibly not just gypsum, which is why the sanding question in an old house starts with a lab. Here is how dust is controlled, what it costs, and the rule for old compound.
The tools, from least to most
| Method | What it does | When |
|---|---|---|
| Good taping | The less compound left on the wall, the less sanding. A taper who wipes clean between coats sands for an hour; one who leaves ridges sands for a day and fills the house. | Always. It is the first dust control. |
| Sponge sanding | A damp sponge instead of paper on the final pass; almost no airborne dust. Slower, and it softens edges. | Small jobs, repairs, occupied rooms. |
| Vacuum pole sander | A sanding head on a hose to a HEPA shop vacuum or a dust extractor. Collects 90% or more at the source. | Every job in an occupied house. Many tapers now use it on new houses too because the cleanup is faster. |
| Poly walls and zipper doors | 6-mil poly taped floor to ceiling across doorways and openings, with a zipper door to get in. Keeps the dust in the work area. | Renovations and basements with the family at home. |
| Negative air machine | A HEPA fan in the work area exhausting outdoors through a window, so air flows into the work area and not out of it. | Full containment in an occupied house; required practice for any abatement. |
| Furnace off, registers sealed, filter changed after | The furnace is the dust distribution system. Off during sanding, returns and supplies taped, a new filter when the dust settles, ducts cleaned if it ran anyway. | Every renovation. Nobody does it, and everyone wonders why there is dust upstairs. |
What it costs and what to ask for
On a new, empty house, dust control is the taper’s own problem and the price is in the rate. In an occupied house, ask for vacuum sanding, poly across the openings and the furnace off, and expect about $250 on top of the taping for a floor or a basement. Full containment with a negative-air machine, zipper doors and floor protection, for a renovation where the family is living on the other side of the poly, is about $600. It is the best $600 in a renovation budget and the contractor who offers it before you ask is the one to hire. The taping calculator has it as a line.
Respirators: an N95 is the minimum for anyone sanding; the professionals wear a half-mask with P100 cartridges. Gypsum dust is a nuisance dust, but the silica in some compounds and the fine particle size are not, and the trade’s lung disease rates say so.
The pre-1990 rule
Joint compound sold in Canada until about the late 1970s commonly contained asbestos, and some products and some textured ceiling finishes continued after that. Ontario’s asbestos regulation (O. Reg. 278/05) names drywall joint compound and textured coatings among the materials that are assumed to contain asbestos in older buildings until a test says otherwise, and sanding or scraping them is a Type 1 or Type 2 operation with specific requirements. In plain words: if the house or the compound is from before 1990 and you are going to sand it, skim it, scrape it or cut into it, a $150 sample to an accredited lab comes first. If it is positive, the work is done wet, contained, by people with the training, and it costs more. If it is negative, you have a piece of paper and you proceed. The full page on asbestos in drywall.
This applies to small jobs too. Sanding the compound on a 1975 wall to repaint it is disturbing the compound. A test is cheap; a DIY shop-vac through old compound is the kind of thing people regret twenty years later.
Where homeowners go wrong
- Leaving the furnace running during sanding. It pulls dust into the returns and blows it into every room, then the filter clogs. Off, sealed, new filter after.
- A bedsheet across the doorway. Dust goes through cloth. Poly, taped, with a zipper.
- Dry-sanding a 1970s ceiling to repaint it. Test first. Every time.
- Sanding to fix bad taping. Oversanding fuzzes the paper and the fuzz flashes under paint. The fix for a ridge is a wider coat, then a light sand.
- Not cleaning the walls before primer. Primer over dust comes off in sheets with the first piece of tape. Vacuum, then a damp microfibre.
Questions people ask
How do you sand drywall without making dust?
A vacuum pole sander on a HEPA extractor catches most of it at the source; a damp sponge for the final pass catches the rest. Poly across the doorways and the furnace off keep what escapes in the room.
Is drywall dust dangerous?
Modern gypsum compound is a nuisance dust with some silica; prolonged exposure without a mask is bad for the lungs and an N95 at least is the rule. Compound from before 1990 may contain asbestos, which is a different category entirely and why the test comes first.
How much does dust control cost?
$250 for vacuum sanding and poly walls on a floor or basement in an occupied house, $600 for full containment with negative air. On an empty new house it is in the taping rate.
Does old drywall mud have asbestos?
It can, in houses built or renovated before about 1990, and Ontario’s regulation treats it as suspect until tested. A single sample to an accredited lab is about $150 and takes a few days.
Price it with the taping
The taping calculator has the dust-control options and the occupied-house factor. For an older house, read the asbestos page before anyone picks up a sander.
Sources and further reading
- Asbestos on construction projects (O. Reg. 278/05): Ontario Ministry of Labour. Drywall joint compound and textured ceilings in older houses are named as materials that may contain asbestos; the regulation says what has to happen before anyone sands or scrapes them.
- Gypsum Association construction standards: GA-216 application and finishing (the hanger’s bible: fastener spacing, ceiling framing limits, joint treatment) and GA-600 fire resistance design manual, with the free downloads.
