Do I need to seal concrete after pressure washing?

Q: How long does concrete sealer last?

Penetrating sealers last 3–10 years, while solvent-based sealers and acrylic sealers last 1–5 years depending on traffic and weather.

Q: Do I need to etch concrete before sealing?

If using a film-forming sealer, yes — acid washing helps adhesion. Not necessary for penetrating sealer.

Do I need to seal concrete after pressure washing? Pressure washing your concrete is like giving it a long-overdue exfoliation. It strips away years of grime, mould, oil, and red dust buildup — especially here in Oz where the climate ranges from monsoonal madness up north to bone-dry winters down south. But once it’s clean and the water drains away, that question always pops up.

The Real Impact on Your Concrete

Think of sealing like sunscreen for your concrete surfaces. Skip it and your surface is out there copping the worst of the Aussie sun, rain, oil stains, tannin stains from gum leaves and the occasional BBQ mishap.

Sealed concrete:

Repels moisture, stains and UV damage
Slows down wear and tear from foot traffic and vehicle traffic
Makes cleaning easier (less dirt and grease sticks)
Looks newer for longer
Offers extra protection against weather-related damage and freeze-thaw cycles

Unsealed concrete:

Soaks up water like a sponge

Prone to mould, mildew and algae build-up (especially in shaded or damp spots)

Can crack or flake in extreme weather conditions

Harder to clean (dirt, concrete stains and fresh oil stains cling on)

Vulnerable to surface damage and potential damage over time

Basically, sealing gives your pressure-washed concrete a fair dinkum chance.

What Happens If You Don’t Seal It?

We’ve seen it time and time again. Brand new slab, cleaned to perfection with a pressure washer… then left bare. Within months:

Mould starts creeping back
Oil stains from the ute leave permanent marks
The sun bakes the surface until it goes patchy and brittle
The driveway becomes a slip hazard when wet

It doesn’t happen overnight, but it always happens faster than you think. And fixing surface damage on concrete projects? That’s a pain in the backside (and your wallet).

Protects, Prevents, and Preserves

Concrete sealing creates a protective layer. Some sealers soak into the concrete (penetrating sealer) to block pores, while others sit on top like a chemical barrier or protective film.
Here’s what a good sealer does:

Blocks water, oil and contaminants from penetrating
Prevents future stains and concrete stains from setting in
Reduces freeze-thaw cycles and cracking
Prevents efflorescence (those chalky salt marks)
Enhances colour and appearance
Inhibits moss and algae regrowth

It also adds a layer of protection or, if you’re using wet-look sealers, a glossy or matte finish depending on your preference.

Don’t Seal It Too Soon

After power washing or acid washing, concrete needs to fully dry before sealing. Sounds obvious, but you’d be surprised how many people slap on a coat of sealer while the slab’s still damp and then wonder why it turned milky or left sticky residue. Checklist before sealing:

Wait at least 24–48 hours in warm, dry weather (longer drying duration if it’s humid or shaded)
No rain forecast
Surface feels bone dry to the touch
Don’t seal in hot weather or under direct sunlight

Top tip: Don’t seal under full midday sun — it can cause bubbling and uneven finish. Seal in the early morning or late arvo.

What Kind of Sealer Should You Use?

Film-Forming Sealers (Acrylic, Polyurethane, Epoxy)

These sit on top and form a protective barrier. Good for high-traffic areas like driveways, pool decks and entertainment zones. Pros:

Adds gloss or matte finish
Maximum protection from stains
Acrylic resin-based sealer creates a smooth finish and protective coat

Cons:

Can be slippery without a grit additive
Will peel if applied over moisture or without proper adhesion
Weather forecast and application timing are sensitive

Acrylic and water-based sealers are easier to apply with a paint roller or paint brush and good for larger surfaces. Acrylic sealants dry faster but solvent-based sealers offer better long term protection.

Penetrating Sealers (Silane, Siloxane, Siliconates)

These soak into the slab and bond with the pores, offering long-lasting protection without changing the appearance.
Pros:

Keeps the natural look of concrete
Excellent water repellence and breathability
Good for residential driveways and outdoor surfaces

Cons:

Won’t stop tough stains or oil as well
No gloss — just a well-maintained concrete surface

What to Avoid

Cheap sealers from hardware chains that wear off fast
Non-breathable sealers that trap moisture and cause sealer adhesion issues
Wrong nozzle when power washing — can gouge the surface, ruining the sealing process
Uneven coverage with a roller method — leads to patchy spots on the entire surface

Do All Concrete Surfaces Need it?

Definitely Seal:

Concrete driveway and garage floors
Exposed aggregate
Pool surrounds and patios
Coloured or stamped concrete
High-use residential driveways

Optional (But Worth Considering):

Plain broom-finished paths
Interior polished floors (may need densifier or special sealers)
Concrete projects in shaded areas are prone to algae

Probably Skip:

Crumbling old slabs
Temporary or rarely used paths
Areas fully protected from sun, rain and foot traffic

Common DIY Mistakes

You can DIY your concrete sealing project — but here are a few ways it can go wrong:

Not cleaning the surface properly — any loose debris or concrete stains will show through the sealer coat
Applying too much sealer — excess sealer leaves sticky residue
Rushing the drying period — always allow sufficient drying time after pressure washing
Poor roller method technique — leads to uneven application or missed spots
Forgetting safety gear like gloves and eye protection
Not using a plastic sheet to test moisture levels before sealing
Using the wrong type of sealer — especially on polished or coloured surfaces
No anti-slip additive — essential for pool decks and outdoor areas

For peace of mind knowing your concrete cleaning and sealing process is done right, call in the professionals. We’ve seen every type of stain from deep stains in driveways to stains under outdoor furniture.

Window Cleaning Melbourne Crew also knows a thing or two about keeping surrounding glass surfaces clean while your concrete cures — worth thinking about if you’re working near windows or pool fencing.