Most paint failures start before the paint is opened. The surface was dirty, glossy, damp or loose. Detroit's old plaster and old wood need more prep than new drywall, and this page explains what that prep is.
Do I need to prime before painting?
You need primer on bare wood, bare drywall, patches, stains, glossy surfaces and big color changes. You usually do not need it on clean, sound, flat paint that is getting a similar color.
Primer does three jobs. It sticks to surfaces that paint alone does not grip. It seals porous spots so the finish dries evenly. It blocks stains from coming through. A paint with primer in it is thicker paint. It does not do those jobs on bare or stained surfaces.
Do I need primer if the old paint is in good shape, and can you paint over old paint?
No primer is needed over old paint that is clean, dull and firmly stuck, and yes, you can paint straight over it. Wash it, fill and spot prime any repairs, and apply the finish coats.
The exceptions are glossy paint, oil-based paint under latex, and paint that is chalky or peeling. Gloss must be sanded dull or primed with a bonding primer. Loose paint must be scraped back to a firm edge.
Do I need to sand the walls before painting?
You need to sand glossy walls, patched areas and rough spots. Flat walls in good shape only need a light scuff or a wash.
Sanding gives the new coat something to grip and levels the edges of repairs. In a house built before 1978, do not dry sand or power sand old paint until you know it is lead free. See our page on lead paint rules in Michigan.
Do painters fix nail holes, cracks and dents first?
Yes. Filling nail holes, small cracks and dents is part of normal prep, and our quotes include it.
Larger repairs are a different thing: holes, loose plaster, long cracks that keep opening, or damaged corners. These are listed separately in the quote because they take more time and material. Plaster cracks in older Detroit homes are often cut open, taped or filled with a setting compound so they do not return through the new paint.
How do I paint over a water stain so it does not bleed through?
Seal the water stain with a stain-blocking primer, then paint. Ordinary latex paint will not hold a water stain back. The brown mark comes through again within days.
Fix the leak first and let the area dry. Then spot prime the stain with an oil-based or shellac-based stain blocker and repaint the whole ceiling or wall section, so the sheen matches. If the plaster or drywall is soft or sagging, it needs repair before primer.
Can you paint over smoke stains or pet smells?
Yes, with the right primer. Smoke and nicotine stains and many odors are sealed in with a shellac-based or oil-based primer before the finish paint goes on.
Wash the walls first to remove as much residue as possible. Paint alone will not stop yellow smoke stains from coming through, and it will not seal a smell. Odors that have soaked into carpet, subfloor or bare wood need those materials cleaned, sealed or replaced as well.
There is mold on the bathroom ceiling. Can it just be painted over?
No. Mold has to be killed and cleaned off first, and the moisture that feeds it has to be dealt with. Paint over live mold peels, and the mold grows back through it.
Small patches of surface mildew on a painted bathroom ceiling can be cleaned, dried, primed with a stain-blocking primer and painted with a bathroom paint. A working exhaust fan matters more than any paint. Larger areas, or mold that comes from a leak inside the wall, are a job for a remediation company. The national figure for small-area mold remediation is $500 to $1,500, as published by HomeGuide for 2026, which is not our quote.
Paint is peeling to bare wood on my old house. What prep does it need?
Paint that has peeled to bare wood needs scraping, sanding of the edges, primer on every bare spot and caulk at open joints before the finish coats.
- Wash off dirt and mildew and let the wood dry.
- Scrape all loose paint back to a firm edge.
- Sand the edges so they do not show through.
- Replace or repair any soft wood.
- Prime bare wood the same day or soon after.
- Caulk gaps at trim and joints, but not the laps that let siding breathe.
- Apply two finish coats.
On a house built before 1978, treat the old paint as lead paint unless it has been tested. That changes how the scraping and clean-up are done.
Why is my paint peeling?
When paint is peeling, the cause is nearly always moisture or poor prep. Either water is getting behind the paint, or the paint was put on a surface that was dirty, glossy, chalky or damp.
Outside in Detroit, the usual causes are failed caulk, clogged gutters, bare end grain soaking up snowmelt, and moisture from inside the house pushing out through wood siding. Inside, it is steam in bathrooms and kitchens, or latex paint over old oil paint. Find the cause before repainting, or it will peel again.
Why is paint bubbling or peeling in my kitchen or bathroom?
Paint bubbles and blisters in kitchens and bathrooms because of moisture and, in kitchens, grease. Steam gets behind a weak paint film and lifts it.
The fix is to scrape and sand the failed area, prime it, and repaint with a paint made for humid rooms. Run an exhaust fan that vents outdoors during and after showers. In kitchens, walls and ceilings near the stove must be degreased before painting, or the new coat will not bond.
How do I know if old paint is oil or latex, and can latex go over oil?
Rub the paint with a rag wet with rubbing alcohol. If color comes off on the rag, it is latex. If nothing comes off, it is oil-based.
Latex can go over oil-based paint only after prep. The oil paint must be cleaned, sanded dull and coated with a bonding primer. Latex put straight onto glossy oil paint peels off in sheets. Old trim and doors in Detroit houses are very often oil-based, so test before choosing a primer.
Do bare drywall patches need primer?
Yes. Drywall patches need primer before paint. Joint compound is more porous than the painted wall around it, so unprimed patches soak up paint and show as dull spots.
Spot prime every patch, then paint the whole wall from corner to corner. Painting only the patch nearly always shows, because new paint and aged paint differ slightly in color and sheen.
Questions about prep on your own house? Call or text (313) 251-3869 for a free estimate.