Short answer: proper wall prep before painting means the surface is clean, filled, smooth and sealed before any colour goes on: nail holes and dents filled, cracks caulked or taped, everything sanded flush, repairs spot-primed, floors and furniture protected. Most of the labour in a quality repaint is preparation, not rolling — which is exactly why the cheapest quote on your table is usually the one that plans to skip it. The paint film is only as good as what it sits on; two coats over an unwashed, unfilled wall fail the same way whatever the brand. Below: the steps in order, the honest line between “prep” and “drywall repair”, where primer is non-negotiable, and the three questions that reveal how much prep a painter actually intends to do.
Prep, step by step
- Inspection with a light. A lamp held against the wall shows every pop, dent and old patch that daylight hides. This is where the door-count and the repair list for the quote come from.
- Washing. Kitchen walls carry grease, hallways carry hand oils, everything carries dust. Paint does not bond to any of it. A wash with a degreasing cleaner, then a rinse, is the least glamorous step and the most skipped.
- Filling and caulking. Nail holes and dings get filler; gaps where trim meets wall get fresh caulk — that caulk line is most of what makes trim look crisp. Hairline cracks get opened slightly and filled, and any crack with history gets taped, not just filled, so it stays closed.
- Sanding. Filled spots sanded flush, glossy areas scuffed so the new coat can grip, and the dust wiped off afterward — sanding dust left on the wall undoes the sanding.
- Spot-priming. Every filled spot and repair gets primer before the finish coats; bare compound absorbs paint differently and telegraphs through as dull patches (“flashing”) if it is not sealed.
- Masking and protection. Floors sheeted, furniture moved and draped, outlets and hardware taped off. The room is handed back clean because it was protected, not because it was cleaned up.
When “prep” becomes a repair
There is an honest boundary between what a painter’s prep includes and what is really drywall work travelling under another name. A useful rule: up to about five small patches in a room — pops, nail holes, a dent — is painter’s prep. Beyond that, or anything structural about the damage, is a repair with its own price, and folding it silently into “prep” is how quotes blow up mid-job.
| What you see | Prep or repair? | Where it goes |
|---|---|---|
| A few nail holes, dents, scuffs | Prep | Included in the painting quote |
| Nail pops and hairline cracks through a newer house | Repair round before paint | Per-repair pricing at $120–200 each, several per visit — the why and how is in cracks and nail pops in new builds |
| A seam with lifting tape, cracked corner bead | Repair | $220–380 per repair — see drywall repair cost in Ontario |
| Water stain, soft or sagging board | Repair, and the leak first | $350–650 per section once the source is fixed — see water-damaged drywall and ceilings |
| A wall full of old patches and waves | Skim coat, quoted on site | Whole-surface work on the drywall repair side, then paint |
A $200 service-call minimum applies to stand-alone repair visits, which is one more reason to have repairs and painting quoted together: one contractor, one schedule, and the walls are genuinely ready when the paint arrives.
Primer: where it is optional and where it is not
Modern “paint and primer in one” products are real, but they solve one problem only: better build and adhesion on a sound, previously painted wall in a similar colour. They do not replace a dedicated primer where chemistry is involved:
- Over repairs and bare compound — spot-prime or the patches flash through the finish.
- Over stains — water marks, smoke, marker bleed through ordinary paint for years; only a stain-blocking (shellac or oil) primer locks them in, and a water stain also needs its leak fixed first.
- Over glossy surfaces and old oil trim — a bonding primer after a scuff sand, or the new coat peels in sheets; the full trim story is in our guide to what trim and doors add to a quote.
- Under and over dark colours — a tinted primer is the difference between two coats and four when going into, or out of, a deep colour.
- On new drywall — a proper drywall primer evens the absorption between paper and compound before the first finish coat.
Three questions that reveal a painter’s prep
- “What does your prep include, written down?” The answer should name washing, filling, caulking, sanding and spot-priming — as lines in the quote, not as a verbal “we prep everything”.
- “What happens when you find damage beyond small patches?” The right answer: we stop, show you, and price the repair in writing before continuing. The wrong answer: “it’s all included” — nothing unlimited is genuinely included.
- “Which primer are you using on the repairs, the stains and the trim?” Any specific answer beats a shrug; a painter who cannot name a primer type is planning to use the wall paint for everything.
These are the same instincts as our contractor-vetting checklist, applied to the prep line — the city-by-city hiring guides for painters in Mississauga carry the full comparison method, and the package rates behind every quote are on our interior painting page with room budgets in interior painting cost in Ontario.
What we include, for the record
On every IntraBuild paint job the Refresh (walls-only) package includes basic prep — filling nail holes, caulking cracks, sanding, spot-priming — plus floor and furniture protection; bigger repairs are itemized per repair so you can see them; and stain-blocking, bonding or tinted primers appear as named lines wherever your walls need them. The quote is written within 48 hours and the person who quotes your job is responsible for the prep and the paint alike, across Toronto, the GTA and Southern Ontario — see interior painting in Toronto — or call (647) 558-8723.
Frequently asked questions
Do I need to wash walls before painting?
Yes — at minimum a dust wipe everywhere and a degreasing wash in kitchens, bathrooms and around switches. Paint over grease or dust bonds to the grime, not the wall, and peels or fisheyes later. It is the cheapest step in the whole job to do and the most expensive one to skip.
Can you paint over nail pops?
You can, and they will be back by spring. A pop is the framing moving, so the fix is mechanical — a screw beside the pop, then filler in coats, then spot-primer. Painting over an unfixed pop just paints a bump. Why new houses grow them is covered in our nail pops guide.
Is paint-and-primer-in-one enough?
On a sound, previously painted wall in a similar colour — usually yes. Over repairs, stains, glossy trim, a dark colour going light or new drywall — no; those need a dedicated spot, stain-blocking, bonding or tinted primer. The label on the can does not change the chemistry on the wall.
How many coats after patching?
Prime the patch, then the same two finish coats as the rest of the wall. On large patches or repaired ceilings, painting the whole wall or ceiling rather than just the repair area is what makes the patch invisible — feathered touch-ups on big repairs almost always show in raking light.
Should trim be sanded before repainting?
Always at least a scuff sand, and on older glossy or oil-painted trim, a scuff sand plus a bonding primer. Enamel applied straight over old gloss is the classic peel-in-sheets failure. The full walls-versus-trim pricing split is in our trim, doors and ceilings guide.