How to Prep a Room Before Interior Painting
Most interior painting problems are prep problems. The paint itself rarely fails on its own; it fails because something underneath it was not ready. That is especially true in Chicago, where a large share of the housing stock is older plaster over lath rather than drywall, and plaster behaves differently under a fresh coat than the newer construction most paint brands are formulated around.
Why older Chicago homes need more prep, not less
Plaster moves with the seasons and with the building itself, so a hairline crack that gets filled and painted over without being addressed properly tends to reopen within a season. The fix is to open the crack out slightly, fill it with a flexible compound rather than a rigid one, sand it flush, and prime the repair before the rest of the wall gets its coat. Skipping that step is the single most common reason a repaint looks fine at handover and shows cracking again within a year.
The prep checklist we actually follow
A proper interior prep sequence looks like this on most jobs:
- Furniture moved and protected, floors covered, fixtures and hardware removed rather than taped around
- Holes and dents filled, hairline cracks opened out and filled with a flexible compound
- Trim and doors de-glossed by hand-sanding so the new coat can actually bond to the old finish
- Spot priming over repairs, or a full prime coat where the surface or color change calls for it
- Caulking gaps at trim, casings and ceiling lines so the finished edge reads clean
- A final wipe-down to remove sanding dust before the first coat goes on
What a professional adds that a rushed job skips
The parts that get cut under time pressure are usually the ones that matter most: full de-glossing of trim instead of a light scuff, a real flexible-compound crack repair instead of a quick smear of filler, and priming that is proportional to the repair rather than skipped to save an hour. None of this shows up in a walkthrough right after the job. It shows up six months later, which is exactly why it is worth checking before you hire, not after.
How much time prep actually adds
On a straightforward room with a few nail holes and no cracking, prep might add half a day to the job. A room with plaster repairs, heavy trim de-glossing, or a significant color change with poor coverage can add a full day or more before the first coat of finish paint goes on. We account for this in the estimate up front, based on what we see at the walkthrough, rather than treating every room as the same amount of prep.
This is part of what is included in every interior painting project we quote – see the full service page for pricing and process.
Frequently asked questions
Paint only lasts as long as the surface under it. Filling, sanding, cleaning, caulking and priming prevent peeling, cracks reappearing and patches showing through the new finish.
Primer is needed over bare drywall, patches, stains, glossy surfaces and old oil-based paint. Sound, previously painted walls in the same color family often only need spot priming.
Cracks are opened, taped and filled, loose areas are stabilized, and the surface is sanded and spot-primed so repairs do not reopen or show through.
Clear small items, electronics and anything fragile, and let the painters know about pets, parking and access. A professional crew will move and cover furniture as part of the job.
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