The right primer is the bridge between your wall prep and your topcoat. Using the wrong primer is like building a house on a bad foundation — the topcoat will fail no matter how good the paint is.
Plaster wall prep requires specialized technique that differs from modern drywall. Most homes built before 1950 — including the vast majority of Washington DC row houses in Georgetown, Capitol Hill, Kalorama, and Logan Circle — have original plaster walls that present unique challenges for interior painting.
HomePro DMV Painters has completed hundreds of plaster wall painting projects in DC row houses. See our drywall repair services for wall restoration options. Our 2-year written warranty covers all prep work.
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Interior painting wall prep cost depends on the condition of your walls. HomePro DMV Painters includes prep in every interior painting estimate — we never quote paint-only pricing because prep is what makes the paint look good.
| Prep Level | Cost/Sq Ft | What's Included | Typical Condition |
|---|---|---|---|
| Light | $1.00–$1.50 | Dust, minor patching, spot priming | Walls in good shape, few nail holes |
| Moderate | $1.50–$2.50 | 10–20 patches, full sanding, caulking, full prime | Lived-in homes, picture holes, minor cracks |
| Heavy | $2.00–$3.00+ | Skim coating, drywall repair, wallpaper adhesive removal, plaster work | Older homes, post-wallpaper, damaged plaster |
See our complete interior painting cost guide for full project pricing including prep, paint, and labor. Prep cost is also affected by your chosen finish — satin finish requires more thorough prep than eggshell because its higher sheen reveals surface imperfections.
Kitchen grease, bathroom soap film, cigarette smoke residue, and plain dust all prevent paint from bonding. You can't see these contaminants on a dry wall — but the paint can feel them. Paint applied over grease will peel within months. Always wash kitchens with TSP and wipe every room with a damp cloth before any other wall prep step. This applies equally to cabinet painting prep — grease buildup on kitchen cabinets is even heavier than on walls.
Lightweight spackle (the pink stuff that turns white when dry) is fine for nail holes. But for anything larger — cracks, dents, screw anchor holes, drywall tape repairs — spackle shrinks as it dries and will crack again within weeks. Use setting-type joint compound (Durabond 45 or 90) for any repair larger than a pencil eraser. It cures by chemical reaction and does not shrink.
A patch that sticks up even 1/16 of an inch above the surrounding wall surface will be visible under fresh paint — it creates a visible bump that catches side light. Sand every patch flush with the surrounding surface using 120-grit, then finish with 150-grit. Run your hand over the repair — you should not be able to feel the edge of the patch.
Unprimed joint compound absorbs paint differently than the surrounding painted wall. The result: visible dull spots called "flashing" where patches absorb the topcoat faster and show as flat, textureless areas against the slightly shinier surrounding paint. Always prime every patched area — spot priming at minimum, full wall priming for best results.
The dark shadow line where baseboards, crown molding, and window casing pull away from the wall is the single biggest visual difference between professional and amateur paint work. Fill every gap with paintable acrylic caulk, smooth with a wet finger, and paint over. This one step makes a $500 paint job look like a $2,000 paint job. Homeowners in Dupont Circle and Woodley Park often notice this immediately in older row houses where trim gaps have widened over decades.
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Wall preparation determines approximately 80% of the final paint result. Paint is a thin film — typically 2–4 mils thick when dry — that reveals every imperfection underneath it. Nail holes, drywall seams, joint compound patches, cracks, peeling paint, and surface contamination (grease, smoke film, marker) will all show through fresh paint if not properly addressed before the first coat goes on. Professional painters spend 50–70% of their total project time on wall prep. HomePro DMV Painters follows a strict 7-step wall preparation process on every interior painting project to ensure a flawless, long-lasting finish.
HomePro DMV Painters follows 7 steps for professional wall prep: Step 1 — Clean the surface (TSP wash for kitchens, dust removal for all rooms, deglossing for previously glossy surfaces). Step 2 — Scrape and remove loose paint (any peeling, flaking, or bubbling paint removed to bare substrate). Step 3 — Patch all holes and damage (nail holes, screw holes, dents, cracks, and drywall damage filled with lightweight joint compound or setting-type compound for larger repairs). Step 4 — Sand smooth (120-grit then 150-grit over all patched areas; 220-grit for final smoothing). Step 5 — Skim coat if needed (full-surface skim with joint compound for walls transitioning to satin finish or for heavily patched surfaces). Step 6 — Caulk gaps (all gaps between trim and wall, along baseboard tops, and around window and door casing filled with paintable acrylic caulk). Step 7 — Prime (appropriate primer for the surface type and paint being applied).
Skim coating — applying a thin layer of joint compound over the entire wall surface and sanding smooth — is necessary in four situations: walls with heavy texture that you want to make smooth (orange peel, knockdown, or popcorn texture removal), walls with extensive patching where multiple repairs would create visible differences in texture under fresh paint, walls being painted in satin or semi-gloss finish (higher sheens reveal surface imperfections that eggshell would hide), and plaster walls with widespread surface deterioration or crazing. Skim coating adds $1–$2 per square foot to the project cost but creates a perfectly smooth canvas for paint. HomePro DMV Painters recommends skim coating when the wall condition and chosen finish demand it.
The right primer depends on the surface condition and what you are covering: PVA primer (Kilz PVA, Zinsser Bulls Eye 1-2-3) — standard for new drywall and minor repairs, seals the porous surface. Shellac primer (Zinsser BIN) — the most versatile; blocks stains, smoke damage, water stains, marker, crayon, and odors; adheres to any surface including glossy paint and bare wood. Oil-based primer (Zinsser Cover-Stain, Kilz Original) — best for severe stains, knots in wood trim, and bare wood surfaces. Bonding primer (Stix, Gripper) — for previously glossy surfaces, ceramic tile, laminate, and surfaces where adhesion is a concern. HomePro DMV Painters uses shellac primer (Zinsser BIN) as the default on 80% of projects because of its universal adhesion and stain-blocking properties.
Plaster walls — common in older homes built before 1950, including most Washington DC row houses — require specialized prep: test for lead paint (pre-1978 homes); scrape any loose or flaking plaster; fill cracks with setting-type joint compound (durabond), not lightweight compound which shrinks in deep plaster cracks; skim coat over repairs to blend with the surrounding plaster texture; sand smooth with 150-grit; prime with shellac primer (Zinsser BIN) which seals the alkaline plaster surface and provides excellent adhesion. Never use PVA primer on old plaster — it does not seal alkaline surfaces properly and can cause adhesion failures. HomePro DMV Painters has extensive experience with DC row house plaster walls.
Professional wall prep costs $1–$3 per square foot of wall surface depending on the level of prep needed. Light prep (dust, minor patching, spot priming) adds $1–$1.50/sq ft. Moderate prep (multiple patches, full sanding, caulking, full prime coat) adds $1.50–$2.50/sq ft. Heavy prep (skim coating, extensive drywall repair, old wallpaper adhesive removal, plaster stabilization) adds $2–$3+/sq ft. Wall prep is included in every HomePro DMV Painters interior painting estimate — we never quote paint-only pricing because the prep is what makes the paint look good. See our interior painting cost guide for complete project pricing.
Yes — satin finish requires more thorough wall prep than eggshell. Satin’s higher sheen (26–40% gloss) reflects light at sharper angles, which highlights every imperfection on the wall surface — patches, seams, sanding scratches, and surface waves that eggshell would hide. For satin finish, HomePro DMV Painters recommends full skim coating on walls with any visible repairs, 220-grit final sanding for a glass-smooth surface, and a full coat of primer to ensure uniform porosity before the topcoat. For eggshell, spot patching and spot priming is usually sufficient. See our eggshell vs satin guide for more on choosing the right finish.
The five most common DIY wall prep mistakes: 1) Not cleaning walls before painting — kitchen grease, bathroom soap film, and dust prevent paint adhesion. 2) Using lightweight spackle for large repairs — it shrinks, cracks, and shows through paint; use setting-type compound for anything larger than a nail hole. 3) Not sanding patches flush — unfilled patches photograph as visible bumps under fresh paint. 4) Skipping primer — paint applied over unprimed patches absorbs differently, creating visible dull spots called “flashing.” 5) Not caulking trim-to-wall gaps — dark shadow lines along baseboards and crown molding ruin an otherwise good paint job. Professional painters caulk every gap before painting.
Wall prep timing depends on the wall condition and room size. For a room in good condition (minor nail holes, light cleaning), prep takes 2–4 hours. For a room with moderate damage (10–20 patches, full sanding, caulking, priming), prep takes 4–8 hours or a full day. For a room requiring skim coating or extensive drywall repair, prep can take 2–3 days including drying time between compound coats. HomePro DMV Painters allocates separate prep days before painting begins — compound and primer need full overnight drying before topcoat application. Our written project schedules show exactly when prep happens vs. when painting happens.
Yes — wall cleaning is the first step in proper interior painting wall prep and the step most commonly skipped. Kitchen walls have invisible grease film from cooking that prevents paint adhesion. Bathroom walls have soap and mineral deposits. All walls accumulate dust. For kitchens: wash with TSP (trisodium phosphate) solution and rinse with clean water. For bathrooms: wash with a degreasing cleaner. For all other rooms: wipe with a damp microfiber cloth to remove dust. For previously painted walls with a glossy finish: lightly sand with 220-grit or use a liquid deglosser to create tooth for the new paint. HomePro DMV Painters includes wall cleaning in every interior painting project.
