If you've been painting houses for more than a month, you already know the truth: prep is the job. The actual painting? That's the easy part.
But here's where most guys mess up — they rush through prep because the customer is watching and they want to look like they're "making progress." Then two months later they're back doing a free touch-up because the paint is peeling off like a sunburn.
Let's fix that. Here's the complete exterior painting prep checklist that'll save your reputation and your profit margin.
Why Surface Prep Makes or Breaks Your Profit
Think about it this way. You spend 2 extra hours prepping a house properly. That costs you maybe $80-120 in labor. Skip it, and you're back in 6 weeks doing a full day of rework — for free. Plus the customer tells their neighbors you did a bad job.
Good prep = no callbacks = more referrals = more money. It really is that simple.
The numbers back it up too. According to paint manufacturers, over 80% of coating failures are caused by improper surface preparation — not bad paint, not bad weather, not bad luck. Bad prep.
The Complete Exterior Painting Prep Checklist
Step 1: Walk the Whole House First
Before you touch a single tool, walk the entire exterior with the homeowner. Point out every issue you see:
- Peeling or flaking paint
- Cracks in siding or trim
- Rotted wood
- Mildew or mold spots
- Caulk failures around windows and doors
- Loose or damaged gutters
Why this matters: This is your CYA moment. If there's rotted wood under three layers of paint, you want the homeowner to know BEFORE you start scraping and suddenly the bill goes up. Document everything with photos. Send them in a text or email.
This walk-through also builds trust. Customers respect contractors who are thorough and upfront.
Step 2: Pressure Wash Everything
You can't paint a dirty house. Period. Every exterior paint job starts with a good wash.
The basics:
- Use 1,500-2,500 PSI for most siding (lower for wood, higher for brick/concrete)
- Keep the nozzle 12-18 inches from the surface
- Work from top to bottom
- Use a cleaning solution for mildew — straight water won't kill it
- Let everything dry completely (usually 24-48 hours depending on weather)
Pro tip: Don't blast the pressure washer directly at windows, under siding edges, or at old caulk joints. You'll force water behind the siding and create moisture problems that show up months later.
Common mistake: Some guys skip the wash on "clean-looking" houses. Don't. There's always a layer of grime, pollen, or oxidation you can't see. Paint won't stick to any of it.
Step 3: Scrape and Sand Loose Paint
This is the part everyone hates, and it's the part that matters most.
What to scrape:
- Any paint that's peeling, cracking, bubbling, or flaking
- Glossy surfaces that need tooth for new paint to grip
- Old drips and runs from previous paint jobs
Tools you need:
- 5-in-1 painter's tool (the Swiss Army knife of scraping)
- Carbide scraper for stubborn areas
- Random orbit sander with 80-120 grit
- Wire brush for detailed trim work
The rule: If it comes off easy, it needs to come off. If you paint over loose paint, your new paint is only as strong as that failing layer underneath. And that layer is already quitting.
After scraping, sand the edges where old paint meets bare wood. You want smooth, feathered transitions — not sharp edges that show through the new paint.
Step 4: Make Repairs Before You Prime
Now's the time to fix everything you found during the walk-through.
Common repairs:
- Fill nail holes and small cracks with exterior-grade wood filler
- Replace rotted boards or trim (don't just fill over rot — it'll come back)
- Re-secure loose siding or trim with stainless steel nails or screws
- Patch any holes in stucco or masonry with appropriate patching compound
On wood filler: Use the two-part epoxy stuff for anything structural or bigger than a pencil eraser. The regular wood filler is fine for nail holes and small dings, but it doesn't have the strength for bigger repairs.
Let all repairs dry and cure completely before moving on. Read the product labels — some fillers need 24 hours to fully cure.
Step 5: Caulk Every Gap and Joint
Caulking is one of those things that separates a $3,000 paint job from a $5,000 paint job. Customers notice clean, sealed joints — even if they can't explain why the house looks so much better.
Where to caulk:
- Around all window and door frames
- Where siding meets trim
- Corner joints in trim boards
- Where different materials meet (siding to brick, wood to stucco)
- Any gap wider than a hairline crack
What to use: Paintable silicone or high-quality acrylic latex caulk (like Big Stretch or Dynaflex Ultra). Don't use cheap caulk. A $6 tube of good caulk saves you from a $600 callback.
Pro tip: Cut the caulk tube tip at a 45-degree angle and keep the opening small. You can always add more — you can't take it back. Use a wet finger or caulk tool to smooth the bead. Sloppy caulk lines are the mark of an amateur.
Step 6: Mask and Protect Everything
This is where being detail-oriented pays off big time.
What to mask:
- Windows (use painter's plastic and tape)
- Door hardware
- Light fixtures
- Address numbers
- Anything you don't want paint on
What to cover on the ground:
- Drop cloths on walkways, decks, patios, and driveways
- Cover plants and bushes with light drop cloths (don't use plastic in direct sun — it'll cook the plants)
- Move or cover outdoor furniture, grills, and decorations
Time-saving tip: Use pre-taped masking film for windows. It costs a little more but saves a ton of time compared to taping and laying plastic separately.
Step 7: Prime Bare Spots and Problem Areas
Not every job needs a full prime coat, but every job has spots that need primer.
Always prime:
- Bare wood (exposed by scraping or repairs)
- Wood filler and patching compounds
- Stains (water stains, smoke damage, knots bleeding through)
- Surfaces switching from oil-based to latex paint
What primer to use:
- Bare wood: Oil-based or shellac primer (best adhesion and stain blocking)
- General exterior: High-quality acrylic primer
- Stains/knots: Shellac-based primer (BIN is the go-to)
Don't skip this. Topcoat paint is not primer. It doesn't bond the same way to bare surfaces, and it won't block stains. Trying to save $50 on primer will cost you when the tannin bleed shows through in a month.
How Long Should Prep Take?
Here's a rough guide for a standard 2,000 sq ft house:
- Minimal prep (house in good shape, just needs wash and light sand): 4-6 hours
- Moderate prep (some peeling, minor repairs, full caulk): 8-12 hours
- Heavy prep (lots of peeling, wood rot, major repairs): 16-24+ hours
The pricing formula most pros use: Prep time should be 50-65% of total job time. If you're spending less than half your time on prep, you're probably cutting corners.
When you're quoting the job, make sure you account for this. A lot of newer contractors price based on painting time only and wonder why they're not making money. The prep IS the job. Price it accordingly.
The "Prep Test" Before You Start Painting
Before you crack open that first gallon of topcoat, do this quick check:
- Run your hand over scraped areas. Smooth? Good. Rough or flaky? Sand more.
- Look at caulk lines from 5 feet away. Can you see lumps or gaps? Fix them.
- Check that primer is fully dry and covering all bare spots.
- Make sure masking is tight with no gaps where paint can bleed through.
- Look at the weather forecast. You need 4-6 hours of dry time minimum, temps above 50°F, and no rain expected.
If everything passes, you're good to go. If not, spend the extra 30 minutes fixing it now. Trust me — it's easier to fix today than it is to explain to a customer next month.
FAQ
How long should I let a house dry after pressure washing?
At least 24 hours for wood siding, 48 hours if it rained recently or the wood is old and absorptive. You can use a moisture meter to check — you want below 15% moisture content before painting.
Can I paint over old oil-based paint with latex?
Yes, but you MUST sand the surface first and apply a bonding primer. Latex won't stick directly to a glossy oil-based surface. This is one of the most common prep mistakes out there.
Should I scrape all the old paint off or just the loose stuff?
Just the loose stuff — unless you're going down to bare wood by choice (which some high-end jobs require). Scrape until you hit paint that's firmly attached, then feather-sand the edges smooth.
How do I know if I'm charging enough for prep work?
If you're not spending at least half your total job time on prep, you're either rushing it or not charging enough. Price prep separately in your estimate so customers understand the value. Most homeowners respect thoroughness when you explain why it matters.
What's the biggest prep mistake you see?
Painting over mildew. Guys pressure wash but don't use a mildew-killing solution, so the mildew is still alive under the paint. Within 6 months, dark spots start bleeding through. Always use a bleach solution or commercial mildew wash, and let it do its thing before rinsing.
Bottom Line
Look, nobody got into painting because they love scraping and caulking. But the contractors who make real money — the ones with full schedules and zero callbacks — they're the ones who take prep seriously.
Do it right the first time. Your bank account will thank you, and your customers will send you their neighbors.
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