Prepping walls is the unglamorous part of painting, but it’s what makes the finish look smooth, even, and “pro.” With a little patience and the right order of steps, you can avoid streaks, peeling, and visible patches.
This guide walks you through how to get walls ready for paint, what it typically costs, and when it’s smarter to bring in a professional.
Typical costs / fees (if applicable)
Prepping walls is often bundled into interior painting quotes, but you can think about costs in a few buckets:
If you’re DIYing the prep
Approximate material costs for a typical bedroom or living room:
- Cleaning supplies:
- Mild detergent or wall cleaner, sponges, rags: $10–$25
- Patching and repair materials:
- Spackle or joint compound: $5–$20
- Putty knives and taping knives: $5–$20
- Drywall repair patches (for small holes): $5–$20
- Sanding and dust control:
- Sandpaper and sanding sponges: $10–$25
- Optional sanding pole: $15–$40
- Plastic sheeting and tape for dust barriers: $10–$30
- Primers and sealers:
- Interior primer (1 gallon): $20–$50 depending on quality and type (stain-blocking, bonding, etc.)
- Masking and protection:
- Painter’s tape: $6–$12 per roll
- Drop cloths or plastic: $10–$40
For a single average room, expect $75–$200 in prep-related materials, depending on how much repair and priming you need and whether you already own basic tools.
If you’re hiring a pro
Most painters roll wall prep into an overall labor quote:
- Basic prep included (light cleaning, filling nail holes, light sanding, basic caulking):
- Often part of a room rate that might be a few hundred dollars and up per room, depending on size and region.
- More extensive prep (lots of patching, crack repairs, heavy sanding, stain blocking, or wallpaper removal):
- Can add $1–$3+ per square foot of wall area or be billed as extra labor hours.
- Serious repairs (water damage, mold remediation, large holes, skim coating entire walls):
- May involve a drywall or remediation specialist and can range from a couple hundred dollars to well over a thousand depending on scope.
Costs go up when:
- Walls have heavy damage or lots of cracks
- There’s smoke, grease, or water staining
- You’re making a dramatic color change (dark to light or vice versa)
- Ceilings are tall or access is difficult
- There are many doors, windows, and trim details to mask
What to expect (process overview)
Step 1: Clear and protect the space
- Move furniture away from walls
- Ideally to the center of the room; cover with plastic or cloth.
- Remove or protect fixtures and hardware
- Take down switch plates, outlet covers, pictures, and curtain rods.
- Loosen light fixtures where possible and tape around bases if you can’t remove them.
- Protect floors and nearby surfaces
- Lay down drop cloths or plastic sheeting.
- Tape plastic to baseboards if you’re worried about dust and drips.
- Create ventilation and dust control
- Open windows if weather allows.
- Close doors to other rooms; use plastic sheeting to create a barrier if doing heavy sanding.
Watch-out: If your home was built before 1978, there’s a possibility of lead-based paint under older layers. Avoid aggressive sanding until you’ve confirmed it’s safe. For suspected lead, contact a certified pro.
Step 2: Inspect the walls closely
Walk the room and mark problem areas:
-
Look for:
- Nail holes, picture hook holes, and small dents
- Hairline cracks, especially around doors/windows
- Peeling or flaking paint
- Water stains or discoloration
- Glossy or slick areas
- Mildew or mold spots (often in bathrooms or near windows)
-
Light trick:
- Use a bright flashlight or work light held at an angle along the wall. Side lighting makes bumps, ridges, and flaws stand out.
Step 3: Clean the walls
Paint sticks best to a clean, dull surface.
- Dust first:
- Use a microfiber cloth, duster, or vacuum with a brush attachment to remove cobwebs and loose dust from walls, corners, and trim.
- Wash where needed:
- For most rooms: a bucket of warm water with a small amount of mild detergent works.
- Kitchens or greasy areas: use a degreasing cleaner suitable for painted walls.
- Rinse lightly:
- Wipe with a clean, damp cloth to remove soap residue.
- Let walls dry completely before patching or priming.
Watch-out: Don’t soak drywall. Use damp, not dripping, sponges and rags to avoid softening the paper surface.
Step 4: Repair holes, cracks, and damaged areas
Match the repair method to the damage:
Small nail holes and minor dings
- Use lightweight spackle or patching compound.
- Apply with a putty knife:
- Press compound into the hole, then scrape off excess so it’s just slightly proud of the wall.
- Let dry fully according to product directions.
Hairline cracks
- Open the crack slightly with the corner of a putty knife to remove loose material.
- Fill with joint compound or spackle, pressing it in firmly.
- For recurring cracks, some pros use fiberglass mesh tape over the crack before applying compound to help prevent re-cracking.
Larger holes (thumb-sized to several inches)
- Use a wall repair patch (self-adhesive mesh or metal-backed patch) sized slightly larger than the hole.
- Apply joint compound over the patch in thin layers:
- First coat: cover the patch and feather edges out 2–3 inches.
- Let dry, sand lightly, then apply a second (and possibly third) coat, feathering further each time.
Peeling or flaking paint
- Scrape off all loose material with a scraper or putty knife.
- Feather the edges with sandpaper so there’s no sharp ridge.
- Spot prime bare or chalky areas with a suitable primer before painting.
Stains, water damage, or mold
- Identify and fix the source first (leaks, condensation, etc.).
- For minor surface stains:
- Clean and let dry, then use a stain-blocking primer before painting.
- For mold or mildew:
- For small, surface-level spots, use a cleaner labeled for mildew on painted surfaces, following safety directions.
- For widespread or recurring mold, or if you suspect moisture inside the wall, contact a remediation or building pro.
Watch-out: If drywall is soft, crumbling, or swollen from water damage, it often needs to be cut out and replaced. That’s typically a job for a drywall professional.
Step 5: Sand for smoothness
Sanding blends repairs into the existing wall so they don’t “telegraph” through the paint.
- Use the right grit:
- Start with 120–150 grit for smoothing patches.
- Finish with 180–220 grit for a finer surface, especially on visible walls.
- Focus on patched areas:
- Sand in a circular motion, blending from the patch into the surrounding wall.
- Feel with your fingertips; it should feel flat and continuous.
- Use a sanding sponge or pole sander for larger areas and to reach higher spots.
- Control dust:
- Vacuum or wipe walls with a barely damp cloth after sanding.
- Keep your respirator or dust mask on while sanding and cleaning.
Watch-out: Don’t oversand and expose the brown paper layer of drywall. That can cause uneven texture and may need sealing with a special primer.
Step 6: Address glossy or uneven surfaces
Paint doesn’t adhere well to slick finishes.
- If walls are glossy or semi-gloss:
- Lightly scuff-sand the surface with fine-grit sandpaper to dull the sheen.
- Wipe off dust.
- Consider a bonding primer designed to stick to glossy surfaces.
- If texture is uneven:
- Multiple patch areas can create a “polka dot” effect under paint.
- In some cases, a thin skim coat of joint compound over a larger area, then sanding, gives a more uniform look. This is more advanced and often best left to a pro.
Step 7: Prime where needed
Primer helps with adhesion, stain blocking, and color uniformity.
You’ll likely need primer if:
- You have patched areas or new drywall
- You’re changing from dark to light or light to very dark colors
- There are stains, smoke damage, or water marks
- The existing paint is glossy or oil-based
- Walls are porous or chalky
Tips:
- Spot-prime vs. full-prime:
- For small repairs on a stable, matte wall, you can often spot-prime patches.
- For many patches, heavy stains, or major color changes, prime the entire wall for best results.
- Use the right primer type:
- General-purpose interior primer for most situations.
- Stain-blocking primer for smoke, water, or marker stains.
- Bonding primer for glossy or tricky surfaces.
- Allow full dry time before painting, especially with stain-blocking products.
Step 8: Tape and mask for clean lines
This is the final step before painting.
- Use painter’s tape around:
- Baseboards and trim
- Window and door casings
- Ceilings where they meet walls (if you’re not painting the ceiling)
- Built-ins and fixtures you couldn’t remove
- Press tape edges firmly with a putty knife or fingernail to reduce bleed-through.
- Mask larger areas (like cabinets or countertops) with plastic or paper attached to the tape.
Watch-out: Remove tape at the right time—usually while the final coat is still slightly tacky or just dry—to avoid peeling off paint. Pull it back on itself at a 45-degree angle.
DIY vs. hire a pro (or self-serve vs. professional)
When DIY wall prep makes sense
You’re likely fine handling prep yourself if:
- Wall issues are minor (nail holes, small dents, light scuffs)
- You’re comfortable with basic tools (putty knife, sander, roller)
- Ceilings are standard height and access is easy
- You’re willing to spend time on details like sanding and taping
Benefits:
- Lower cost if you already own some tools
- Full control over how meticulous the prep is
- Good learning experience if you plan more projects
When to lean on a professional
Consider hiring a pro if:
- Your home is older (pre-1978) and you suspect lead paint
- There’s significant cracking, bubbling, or peeling across large areas
- You see water damage, mold, or mildew that keeps coming back
- Walls need skim coating or extensive texture repair
- Ceilings are very high or require ladder or scaffold work
- You’re short on time and want a fast, consistent result
Safety and quality reasons to choose a pro:
- Lead and dust control: Certified pros know how to contain dust and handle hazardous materials safely.
- Structural or moisture issues: Pros can spot underlying problems (like leaks or settling) that need attention before painting.
- Finish quality: Experienced painters can blend repairs and textures so they’re virtually invisible.
If you decide to hire out, you can use a service like Home Services Scout to compare local painting and drywall pros, read reviews, and get a sense of pricing before you commit.
Questions to ask before you commit
Whether you’re hiring a pro or deciding how to DIY, it helps to be clear on a few points:
- What condition are my walls really in?
- Do I just have nail holes, or are there cracks, stains, and peeling paint that need more advanced repair?
- Is there any chance of lead paint or asbestos?
- Especially in older homes, ask a pro how they test and what safety measures they use.
- What prep is included in a painter’s quote?
- Does the price cover patching, sanding, caulking, and priming, or are some items extra?
- How will you handle dust and cleanup?
- Will they use plastic barriers, floor protection, and HEPA vacuums? Who handles final cleanup?
- What products will be used for primer and repairs?
- Are they using stain-blocking or bonding primers where needed? What kind of patching compounds?
- How will you deal with stains, water damage, or mold?
- Do they repair the source of the problem or just cover it up?
- How many coats of primer and paint are planned?
- Especially important for big color changes or heavily patched walls.
- What’s the timeline from prep to final coat?
- How many days will the room be disrupted, and in what order will they work?
- How do you ensure smooth, even walls?
- Ask about sanding between coats, checking with side lighting, and dealing with texture differences.
- Is the work guaranteed?
- If cracks reappear or stains bleed through, will they come back to fix it?
Quick FAQ
Do I really have to prime before painting?
Not always, but you should prime when you have patched areas, stains, glossy surfaces, or a big color change. Skipping primer in those situations often leads to uneven color, poor adhesion, and visible patches.
How long should I wait after patching to sand and paint?
Follow the product label, but many spackles and joint compounds need a few hours to overnight to dry fully, especially in thicker layers. If it feels cool or soft to the touch, wait longer before sanding or priming.
Can I just paint over small nail holes?
You’ll get a much better result if you fill, sand, and spot-prime even tiny holes. Paint alone tends to sink into the hole and leave a visible dimple.
What’s the biggest mistake people make when prepping walls?
Most homeowners rush the sanding and skip primer where it’s needed. That’s what leads to visible patch outlines, flashing (shiny spots), and paint that peels or chips sooner.
Wrap-up / next steps
A smooth, pro-looking paint job starts long before you open the paint can. If you take the time to clean, repair, sand, prime, and tape carefully, your final coat will go on easier and look better for years.
Next steps:
- Walk your walls and make a list of repairs and prep tasks.
- Decide what you’re comfortable doing yourself and where you’d prefer help.
- Compare 2–3 quotes from local painters or drywall pros so you understand pricing and what’s included.
If you’d like to see options quickly, you can use Home Services Scout to compare nearby painting and home repair professionals, check reviews, and request estimates before you commit to a project plan.