Pressure Washing Precast Concrete — How to Clean It Safely and Effectively
Apr 19, 2026Pressure Washing Precast Concrete — How to Clean It Safely and Effectively
By Jason Geiman, King of Pressure Wash | 134,000+ views on YouTube
Precast concrete is one of those surfaces that looks intimidating to clean if you've never done it before. It's textured, porous, and often covered in years of accumulated grime, algae, and environmental staining. But with the right approach, precast concrete cleans up beautifully — and cleaning precast buildings can be a very profitable commercial service to add to your pressure washing business.
I've been cleaning precast concrete buildings and surfaces for over 15 years as part of my commercial pressure washing work. In this post, I'll walk you through how to approach precast concrete cleaning — from the equipment you need to the technique and chemical selection that will get you professional results without damaging the surface.
About Jason Geiman
Founder, King of Pressure Wash | 51,800+ YouTube Subscribers | 2,000+ Videos
Jason Geiman has been in the pressure washing industry for over 15 years, running his own pressure washing company and training thousands of contractors through his online courses, in-person training events, and weekly live streams. He is the founder of KingOfPressureWash.com and has built one of the largest pressure washing education communities in the world.
What Is Precast Concrete?
Precast concrete is concrete that's manufactured in a controlled factory environment, cast into molds, cured, and then transported to the job site for installation. It's commonly used for commercial building facades, retaining walls, parking structures, sound barriers, and architectural panels. The surface can range from smooth to heavily textured depending on the mold and finish used during manufacturing.
What makes precast different from poured-in-place concrete is the surface texture and density. Precast panels often have an exposed aggregate finish, a sandblasted texture, or a form-liner pattern that creates a decorative look. These textures trap dirt, algae, and pollution deep in the surface — which is why precast buildings get dirty faster and look worse than smooth concrete surfaces.
Equipment for Precast Concrete Cleaning
You need a commercial-grade pressure washer. Precast concrete cleaning is commercial work, and you need a machine that can deliver the flow and pressure for the job. A 4 GPM machine at 3,500-4,000 PSI is a good starting point, but higher-GPM machines (5.5-8 GPM) will make you significantly more productive on large commercial buildings.
A surface cleaner is essential for horizontal precast. If you're cleaning precast walls or walkways that are horizontal, a surface cleaner gives you even, streak-free results much faster than a wand alone. For vertical panels and building facades, you'll be working with a wand and the right nozzle selection.
Chemical application equipment. You'll need a way to apply cleaning chemicals to the precast surface. A downstream injector works for accessible areas, but for large commercial buildings, a 12-volt pump system gives you more control and the ability to apply stronger chemical mixes. For tall buildings, you may need a dedicated chemical application setup that can reach the upper floors.
Lift equipment for multi-story buildings. Cleaning a multi-story precast building from the ground isn't practical. You may need a boom lift, scissor lift, or scaffolding to access the upper portions of the building. Factor this into your bidding — lift rental is a significant cost that needs to be included in your price.
The Cleaning Process
Step 1: Pre-wet the surface
Before applying any chemical, wet the precast surface with clean water. This prevents the porous concrete from absorbing too much chemical and helps the cleaning solution spread evenly. For vertical panels, work from the bottom up to prevent dirty water from streaking down dry concrete.
Step 2: Apply your cleaning chemical
For organic growth (algae, mold, mildew), a sodium hypochlorite solution with a surfactant is the go-to. Apply from the bottom up on vertical surfaces. For heavy environmental staining, pollution, and carbon deposits, you may need a specialty concrete cleaner or a combination of bleach and a degreaser. Let the chemical dwell for 5-10 minutes, keeping the surface wet.
Step 3: Pressure wash the surface
Rinse from the top down using appropriate pressure for the precast finish. Smooth precast can handle more pressure than heavily textured or exposed aggregate finishes. Use a 25-degree or 40-degree nozzle and maintain enough distance from the surface to avoid etching or damaging the concrete. The chemical does the heavy lifting — the pressure wash is really just removing the loosened grime.
Step 4: Rinse thoroughly
Make sure you rinse all the chemical residue off the surface. Chemical left on the concrete can leave white residue or discoloration as it dries. Do a final rinse pass from top to bottom, making sure you don't leave any chemical streaks or missed spots.
Common Challenges with Precast
Textured surfaces hold more dirt. The deeper the texture, the harder it is to get the surface completely clean. Exposed aggregate finishes have lots of nooks and crannies where dirt and algae hide. You may need to make multiple passes or use a stronger chemical mix on heavily textured precast.
Streaking on vertical panels. If you don't pre-wet properly or if you apply chemical from the top down on vertical surfaces, you'll get streaks where dirty chemical runs down over dry concrete. Always pre-wet and apply chemical from the bottom up.
Uneven cleaning results. Precast panels that have been exposed to different amounts of sun, shade, and moisture will have different levels of staining. North-facing panels are typically dirtier than south-facing ones. You may need to adjust your chemical strength or dwell time for different sides of the building.
Runoff and environmental concerns. Commercial precast cleaning produces a lot of runoff water that contains chemicals and loosened contaminants. Check local regulations on wastewater management. You may need to contain and collect the runoff, especially near storm drains. This is part of being a professional operation.
Bidding Precast Concrete Jobs
Precast concrete cleaning is typically priced by the square foot. Your price per square foot will depend on the height of the building (do you need a lift?), the severity of the staining, the type of precast finish, and accessibility. Multi-story buildings with heavy staining that require lift equipment will obviously command a higher price per square foot than a single-story retaining wall.
Don't forget to factor in your chemical costs, which can be significant on large commercial buildings. Also factor in the time for setup, lift rental, mobilization, and cleanup. Commercial precast jobs tend to be higher-ticket than residential work, so they're worth pursuing once you have the equipment and experience to handle them.
Want to Land More Commercial Pressure Washing Jobs?
Jason Geiman covers commercial bidding, equipment selection, chemical mixing, and business strategy in his training courses and weekly live streams.
Visit KingOfPressureWash.com to Learn MoreFrequently Asked Questions
Can you pressure wash precast concrete?
Yes. Precast concrete can be safely pressure washed using the right combination of chemical pre-treatment and appropriate pressure. Pre-wet the surface, apply a cleaning solution (sodium hypochlorite with surfactant for organic growth), let it dwell, and rinse with a 25-degree or 40-degree nozzle at an appropriate distance.
What chemical do you use to clean precast concrete?
For organic staining like algae, mold, and mildew, sodium hypochlorite (bleach) with a surfactant is the standard. For heavy environmental staining, pollution, and carbon deposits, specialty concrete cleaners or degreasers may be needed. Always pre-wet the surface before applying chemical.
How do you bid precast concrete cleaning jobs?
Precast jobs are typically priced by the square foot. Your rate depends on building height, staining severity, surface texture, accessibility, and whether lift equipment is needed. Always do an in-person site visit before quoting. Factor in chemical costs, equipment rental, setup time, and wastewater management.
What PSI should I use on precast concrete?
The PSI depends on the finish. Smooth precast can handle standard pressure washing pressure (3,000-4,000 PSI at distance), while heavily textured or exposed aggregate finishes should be cleaned with lower pressure and more chemical work. The chemical does most of the cleaning — the pressure wash removes the loosened grime.
Is precast concrete cleaning profitable?
Yes. Commercial precast cleaning is a high-ticket service that typically commands better per-hour rates than residential work. The jobs are larger, recurring (commercial properties often clean annually), and less price-sensitive than residential customers. You'll need commercial equipment and possibly lift access, but the margins are strong.
