What To Use To Wash Your Home’s Exterior Before You Paint

Brandon Ryan
Jul 10, 2025
6 min read

The right wash can make or break your paint job. Use pressure washing for tough, durable surfaces, soft washing for delicate siding, or hand scrubbing with TSP or biodegradable cleaners for precision. A clean surface ensures your paint bonds well and lasts for years.

Here’s how each method works best:

Pressure washing – Fast, deep cleaning for vinyl, block, and concrete
Soft washing – Gentle on stucco, wood, and leak-prone areas
Hand scrubbing – Perfect for trims, peeling paint, or delicate surfaces
TSP or biodegradable cleaners – Remove grime, de-gloss, and prep for adhesion

At ProSmart Painting, we never paint over dirt or mildew. Our team selects the safest, most effective wash for your siding so your new paint job looks great and holds up in Arizona’s harsh climate.

Keep reading to learn which cleaning method is right for your home, and the mistakes to avoid before you start painting.

3 Main Methods to Wash Exterior Before Painting

Cleaning your home’s exterior doesn’t mean grabbing a hose and calling it good. There are three main washing methods, and each one fits a different situation. Choosing the wrong one can cause more harm than good, or leave your surface improperly prepped.

Let’s break them down.

1. Pressure Washing

Best for: Vinyl siding, concrete block, fences, and other durable surfaces.

Pressure washing is the go-to method for many professionals because it’s fast, effective, and reaches places hand scrubbing can’t. It blasts away dust, grime, pollen, loose paint, and mildew in one pass.

But here’s the catch: when used improperly, a pressure washer can do damage. We’ve seen DIYers etch wood siding, saturate walls with water, and even spray paint off surfaces they wanted to keep.

Too much pressure can force moisture deep into porous materials, requiring extended drying time. And if you’re thinking of washing now and painting two weeks from now? That’s risky. Even in dry climates, dust and pollen can settle again. If it's been more than 7 days since washing, we always recommend a light rinse.

2. Soft Washing

Best for: Stucco, older wood, trim, or homes with known leak issues.

Soft washing uses a low-pressure sprayer to apply a cleaning solution, often biodegradable and pet-safe. It’s gentle on delicate materials and ideal when water intrusion is a concern.

In our experience, soft washing is especially effective in shaded areas or humid climates where mildew thrives. It’s also the preferred method for homes with questionable window seals or historical siding that can’t handle a high-pressure blast.

Homeowners with outdoor kitchens often ask if smoke or grease from BBQs will affect the paint. It can. Residue builds up invisibly over time. Degreasers paired with soft washing can solve that without damaging the surface.

3. Hand Scrubbing

Best for: Small areas, trims, delicate surfaces, or homes where power access is limited.

Sometimes, old-fashioned elbow grease is the safest route. With a scrub brush, a bucket of TSP or Simple Green, and a water source, you can control exactly how much pressure is applied.

This method works especially well when prepping wood that’s peeling or previously painted in gloss. Just make sure to rinse thoroughly and let it dry completely.

Some folks ask if they can use Dawn dish soap instead of a commercial cleaner. You can, but it may not be strong enough for mildew, grease, or glossy paint. It also doesn’t de-gloss surfaces the way TSP does.

What Cleaners Should You Use? (And Which to Avoid)

Safe & Effective Options

Choosing the right cleaner can make all the difference, especially when you want a finish that lasts.

Krud Kutter House Wash: Biodegradable, non-toxic, and safe for plants and pets.
Jomax + Bleach: Great for mildew-prone areas like shaded sides of the home.
TSP or TSP Substitute: Ideal for de-glossing, degreasing, and deep cleaning before painting.

Rinsing with a hose might work for loose dust, but it doesn’t tackle what you can’t see, grease, airborne pollutants, or microscopic mildew spores.

Avoid These Mistakes

Cleaning might seem simple, but one misstep can compromise your entire paint job.

Don’t let chemicals dry in direct sunlight. It can stain or bleach siding.
Always wet plants before and after cleaning to prevent chemical burn.
Never run bleach through a pressure washer’s injector. It can corrode internal parts and kill vegetation.
Don’t forget to rinse. Even biodegradable cleaners can leave residue that stops paint from bonding.

How Long Should You Wait After Washing?

Dry time matters just as much as the washing itself.

Pressure washing: Wait at least 2–3 days.
Soft washing or hand scrubbing: 1–2 days is usually enough.

In cold, damp, or shaded areas? Add more time. Moisture gets trapped deep in siding and takes longer to escape.

If you're painting during monsoon season or after a storm, don’t rush it. Painting too soon locks in that moisture, causing bubbling or mildew underneath the paint.

If you washed more than a week ago and haven’t painted yet, give the surface another rinse. Wind and ash, especially in fire-prone regions, can undo your prep work in a single afternoon.

The Risks of Skipping Proper Washing

We’ve had to repaint homes just months after a competitor “finished” the job. Why? Because they skipped the wash.

Mildew, chalky residue, and loose paint will all break down your topcoat prematurely. No paint, no matter how expensive, can perform on a dirty surface.

We don’t paint over dirty exteriors. If a home isn’t clean and dry, we won’t move forward. That’s one of the many reasons our clients trust us to do it right the first time. Need help? Contact ProSmart Painting.

When to Call the Pros vs. DIY

Call ProSmart When:

Your home has mildew, soft wood, or past moisture damage.
You’re unsure whether to use TSP, bleach, or a biodegradable cleaner.
Your siding type is unknown or sensitive (like EIFS or historic wood).
You want a long-lasting result without repainting every few years.

DIY Is Fine If:

You have easy-access siding and safe ground-level work areas.
You’re confident using degreasers, brushes, and rinsing tools properly.
Weather conditions are dry, warm, and predictable for at least 5–7 days.

Even if you plan to DIY, we’re always here to offer valuable prep advice, or double-check your prep before we apply professional-grade paint.

How ProSmart Painting Does It Better

Most painting companies treat washing as a checklist item. We don’t.

Surface preparation is one of the pillars of our process. We inspect, clean, repair, and prep every square inch before a drop of paint touches your home. Why? Because that’s the part no one sees, but it determines everything.

We never paint over unwashed siding, and we never rely on pressure washing alone to do the job. Every home is different. Some need soft washing to protect aging wood or prevent water intrusion. Others need hand scrubbing for delicate areas. Our team knows the difference and treats your home accordingly.

We also don’t cut corners to speed things up. No “paint and primer in one” gimmicks. No watered-down products. And no upfront deposit. We provide everything, from the cleaners to the paint, and only get paid when the job is complete and you’re 100% satisfied.

If you’ve dealt with contractors who over-promised and under-delivered, we’re here to earn your trust back, one properly prepped surface at a time.

Ready to Get the Perfect Finish?

ProSmart Painting believes in doing things the right way. We know that painting your home is about protecting your biggest investment and creating a space you’re proud of.

That starts with a clean surface.

Our team will handle everything from washing to final walkthrough with precision and care, so you don’t have to worry about bubbling paint, missed spots, or costly redos.

We’re here to serve homeowners who value quality and trust. If you’re in Phoenix or the surrounding areas and want a team who will treat your home like their own, just give us a call. We’d love to help you get that perfect finish.

Frequently Asked Questions (FAQ)

Can I just paint over old paint that won’t scrape off?

If it’s stuck tight, sand it down or use TSP to dull the gloss. But if it’s flaking or chalking, you’re wasting your time and money.

What if I don’t know what my siding is made of?

If you’re not sure whether you have stucco, EIFS, or cement board, get it identified. Each has specific cleaning and prep needs. Our team can help assess it on-site.