TL;DR
Degrease the whole slab before any pressure touches it, then work in even overlapping passes with a surface cleaner rather than a wand. Concrete is one of the few residential surfaces that genuinely tolerates 2,500 to 3,500 PSI, but the common failure is not damage -- it is a striped, patchy finish caused by uneven technique.
Why the whole slab gets pre-treated
The instinct is to wash the driveway and then attack the stains that remain. That order is what creates stripes.
Chasing a stain means lingering on it while the rest of the slab moved at a normal pace. The stain lifts, and so does more of the surface film around it, leaving a bright patch that no amount of blending fixes.
Pre-treating flips the problem. A cleaner or degreaser applied across the whole slab and given dwell time brings everything to the same readiness, so a single even pass produces a uniform result.
Source: concrete cleaning contractor practice guidance
What you need
- A concrete cleaner or alkaline degreaser sized to the slab area
- A pump sprayer or a hose-end applicator for the cleaner
- A stiff push broom or a deck brush
- A pressure washer, ideally 2.5 GPM or better
- A rotating surface cleaner attachment sized to your machine flow
- A wand with a 25 degree tip for edges
- Eye protection and closed shoes
Sizing matters on the attachment. A surface cleaner rated above your machine flow will spin slowly and leave curved arc marks, which is the same striping problem in a different shape. Sizes and minimum flows are in a surface cleaner compared with a wand.
Step by step
1. Clear and sweep. Move vehicles, planters, and anything loose. Sweep off leaves, gravel, and dirt -- washing loose debris just moves it around and clogs the surface cleaner skirt.
2. Protect the surroundings. Soak plants and grass along the edges with plain water and keep them wet. Check where the runoff will go and whether local rules require keeping it out of storm drains.
3. Pre-wet the slab. Concrete is porous, and a dry slab pulls cleaner deep into it. Wetting first keeps the product working at the surface where you need it.
4. Apply the cleaner across the entire slab. Follow the dilution on the label. Work in sections if the driveway is large enough that the far end would dry before you get back.
5. Let it dwell. Usually five to ten minutes. Never let it dry -- mist with plain water if a section starts to go dry, since dried cleaner leaves its own residue mark.
6. Agitate heavier areas with a stiff broom. Traffic lanes, the apron, and anywhere under a parked vehicle get the most attention.
7. Wash with the surface cleaner. Start with the disc already flat on the concrete, walk at a steady pace, and overlap each pass by two to four inches. Work in one consistent direction across the whole slab rather than in patches.
8. Cut the edges with a wand. A 25 degree tip, held at a fixed distance, feathering into the cleaned field while everything is still wet so the transition blends.
9. Rinse the whole slab and flush the surrounding grass, beds, and walkways so nothing dries on them.
The technique details that decide how it looks
Consistent distance. Move your feet rather than sweeping your arm. An arc swept from a fixed shoulder puts the wand closer in the middle of the stroke than at the ends, and the concrete records that.
Consistent speed. Slowing down at the end of a stroke or pausing to reposition leaves a spot that got extra cleaning. Release the trigger before you reposition.
Consistent overlap. About half the width of a wand pass, two to four inches with a surface cleaner.
Watch the light. Stand so the sun rakes across the slab and you can see the wet pattern as you work, which is the only time it is still fixable.
The full diagnosis of banding is in avoiding stripes and lap marks on concrete.
Stains that need their own treatment
Some marks are not going to move with a general cleaner.
Oil and transmission fluid have soaked into the pores and need an absorbent first, then a degreaser with real dwell time, then possibly a poultice for old stains. That sequence is in removing oil stains that have soaked in.
Rust from planters, patio furniture feet, fertilizer, or well water needs an oxalic-type product rather than a general cleaner. Do this as a separate operation and rinse completely between products -- see removing rust stains without etching the slab.
Tire marks are usually rubber transfer and respond to a degreaser and agitation rather than more pressure. Leaf and tannin staining often lifts with an oxygen-based cleaner and time.
Never combine a bleach-based cleaner with an acidic product such as a rust remover or a masonry etcher. That combination releases chlorine gas. Finish one, rinse the slab until the runoff runs clear, and only then start the other.
When to go gentler
Not every slab is a candidate for full pressure.
Spalling or flaking concrete is already failing, and pressure accelerates it. Wash it gently and accept a modest result.
Exposed aggregate can lose the mortar holding the stones. Lower pressure, wider tips.
Sealed or stamped concrete is a coating job, not a concrete job, and full pressure will damage the sealer.
New concrete should cure before it is pressure washed, generally at least a month, and longer is safer.
Cracks and joints take water underneath. Do not hold a stream on a crack; you are washing out the base.
Sealing, and how often to do this
Most driveways benefit from a wash once a year, more under heavy tree cover where organic staining and algae build faster.
Sealing after cleaning slows re-staining, but it commits you to a maintenance cycle and changes how the slab looks, and the concrete must be completely dry first -- usually several days after washing. If the slab is sealed already, a gentler wash preserves the sealer rather than stripping it unevenly.
FAQ
How do you clean a concrete driveway?
Sweep it clear, pre-wet the slab, apply a concrete cleaner or degreaser across the whole surface, let it dwell five to ten minutes without drying, agitate heavy areas with a stiff broom, then wash with a surface cleaner in even overlapping passes and finish the edges with a wand.
What PSI should I use on a driveway?
Sound, cured, unsealed concrete tolerates roughly 2,500 to 3,500 PSI, though flow rate determines how long the job takes more than pressure does. Spalling, exposed aggregate, sealed, stamped, or newly poured concrete all need considerably less than that.
Do I need a surface cleaner attachment?
Not strictly, but it changes the outcome. A surface cleaner rides at a fixed height with rotating arms, so it delivers even energy across a wide band and finishes a driveway in a fraction of the time a wand needs, without the striping a hand-swept wand tends to leave.
Should I use a cleaner before pressure washing concrete?
Yes for anything beyond light soil. Pre-treating the whole slab means stubborn areas release at the same rate as everything else, which removes the temptation to linger on a stain and create a bright patch you cannot blend out afterward.
Why does my driveway look patchy after washing?
Because some areas received more cleaning energy than others -- usually from chasing individual stains, from an inconsistent pace, or from a swept arc that changed the wand distance mid-stroke. The remedy is re-washing the whole slab evenly while it is still wet.
Flat concrete is one of the few exterior surfaces that genuinely rewards real pressure, and the result comes down to pre-treatment and consistent passes. Our pressure washing service handles driveways, walkways, and edges as one job. Get a quote and we will size it with you.