Hurricane Prep Charleston: What to Pressure Wash Before You Board Up
Hurricane prep in Charleston usually starts with plywood and ends with us getting calls about mildew on Hardie siding that should've been cleaned in spring. Most of what people want washed 48 hours before landfall either won't matter or can't dry in time. The stuff that does matter gutters, storm drains, maybe your driveway if you're staging sandbags takes maybe two hours if you know what you're doing.
Why Pressure Washing Before a Hurricane Usually Backfires
I get the impulse. A hurricane's coming, you want everything cleaned up and buttoned down. But pressure washing 24 to 48 hours before landfall creates more problems than it solves.
Wood siding needs three to five days to dry completely in our climate (Charleston averages 78% relative humidity from June through September, the highest sustained humidity in South Carolina according to NOAA). Vinyl stays slick for 36 hours minimum. If you wash on Tuesday and the storm hits Thursday night, you're boarding up windows on wet surfaces that won't take tape properly. Plywood anchors pull easier from damp wood. And if you're scrambling to move patio furniture or tie down the grill, the last thing you need is a slippery deck.
The bigger issue is time. I watched people wash their driveways the day before Helene hit in September 2024 when they should've been clearing storm drains and trimming loose palm fronds. The driveway's going to be covered in debris and salt spray within 12 hours of the first squall anyway. You just burned four hours you needed for actual prep.
We don't schedule exterior washes within a week of a forecast track entering the cone. Not because we're worried about the work, but because it's the wrong priority at the wrong time.
The One Thing You Should Wash: Gutters and Downspouts
This is the exception. Clogged gutters turn into battering rams when they're holding 40 pounds of wet oak leaves and standing water. I've seen them rip fascia boards clean off Mount Pleasant houses during Hurricane Matthew in 2016 (National Weather Service Charleston). The gutter didn't fail. The weight just overwhelmed what six screws could hold.
You don't need to pressure wash gutters before a storm. You need to clear them. Big difference. If the hurricane's inside 72 hours and you haven't touched your gutters since spring, here's the fast way: get a leaf blower with an extension tube, blow everything toward the downspouts, then flush with a garden hose. Takes 20 minutes for a typical single-story Charleston house. No ladder required if you've got a two-story extension kit.
Check the downspout outlets at ground level. Pull out any magnolia leaves or pine straw clumps by hand. During a storm, your gutters need to dump water fast. If the downspout's choked, the gutter overflows onto siding or pools against your foundation. Neither's good.
We carry gutter cleaning gear on every truck specifically because it's the one task that actually prevents damage in the 48 hours before landfall. Everything else you wash is cosmetic or can wait. Gutters holding water become projectiles. Clear them first, board windows second.
What Not to Wash: Decks, Fences, and Anything Wood
Pressure washing wood 48 hours before a hurricane is one of the fastest ways to guarantee damage. The wood soaks up water, swells, and then gets hammered by wind before it has time to dry. We've seen this wreck Sullivans Island decks after Matthew and split fence pickets all over Mount Pleasant before Irma. The boards curl at the edges. The grain lifts. Sometimes they just crack clean through.
Wood needs at least 72 hours to dry after a wash. Preferably a week if you're using any bleach solution to kill mildew. When you pressure wash, you're forcing water deep into the grain (even at low PSI). That's fine in normal conditions. The sun pulls it back out over a few days. But if a storm rolls in while the wood's still saturated, you've got fibers expanding and contracting under wind load. That's when deck boards pop screws and fence rails split along the fastener lines.
Charleston single-house siding is especially vulnerable. Those cypress boards have been drying for a hundred years in some cases. You wash them Thursday, the hurricane hits Saturday, and suddenly you're looking at warped siding that won't sit flush anymore. We've patched three Isle of Palms houses where owners cleaned right before Helene and the siding cupped so badly they had to replace entire sections.
If your deck or fence has visible mildew and you're worried about storm prep, just leave it. Mildew doesn't get worse in 48 hours. The wood won't rot between Tuesday and Thursday. Clean it after the storm passes and you've cleared debris. At that point you'll know what actually needs attention versus what just looks dirty.
Driveways and Walkways: Only If They're a Slip Hazard
I'm not saying wash your whole driveway. I'm saying handle the spots where algae has turned concrete into a skating rink. The path from your garage to the street where you'll be hauling plywood. The back walkway to your generator shed. The front steps where you're going in and out twenty times grabbing batteries and flashlights.
This is a 20-minute job with a surface cleaner. Not a detail. You're targeting the green slick, not the oil stains or rust shadows. We run 1,500 PSI with a rotating head, no soap, just mechanical scrub. Start at the highest point and work downhill so the runoff carries the algae debris away from where you're walking.
Concrete dries fast. Even in Charleston humidity, a driveway's walkable in two hours and fully cured in eight. That's the difference between concrete and wood (where you need three days minimum). You can clean a walkway Tuesday morning and load sandbags that afternoon without worrying about structural problems.
Skip the decorative pavers unless they're genuinely slippery. Skip the entire driveway if only one section near the street is algae-covered. This isn't about curb appeal. It's about not eating it while you're carrying a sheet of plywood in the rain at 11 p.m. because the outer bands just arrived and you realized your workshop window still isn't boarded.
After the Storm: What to Wash First to Prevent Permanent Damage
You've got 72 hours. That's the window before salt spray and pluff mud go from surface film to chemical stain that won't rinse off without an acid wash or paint job.
After Helene last September, we had homeowners calling a week later asking why their vinyl shutters looked bleached. They weren't bleached. The salt had etched the pigment layer. Same thing happens to painted wood trim, aluminum window frames, composite decking. If you wait ten days, you're repainting or replacing, not cleaning.
Here's the triage order we run on Sullivans Island and Folly Beach after every big blow. Windows first (salt spray bonds to glass faster than any other surface and blocks your view of structural damage). Then siding, especially on the windward side where the salt concentration is highest. Then railings and exposed metal (corrosion starts within 48 hours in Charleston's 78% summer humidity). Driveways and walkways can wait a week unless you've got standing saltwater that'll stain the concrete.
One thing most people don't think about: your insurance adjuster wants to see storm damage, not clean surfaces. If a gutter's torn off or a soffit's peeled back, photograph it before you wash. We've had claims denied because the homeowner pressure-washed everything immediately and the adjuster said "we can't verify wind damage versus deferred maintenance." Document first. Rinse second.
The actual wash is straightforward. Low pressure (1,200 PSI max), no soap, just mechanical rinse. You're not deep-cleaning. You're flushing corrosives off before they set. Start high, work down, let gravity pull the salt and mud away from the foundation. This isn't the time for detail work or mildew treatment. That comes later when your roof's patched and your power's back and you're not operating on a generator and three hours of sleep.
The Spring Hurricane Prep Timeline (Not the August One)
Most people wait until a cone shows up on the Weather Channel. By then you're competing with 200,000 other homeowners for plywood, contractors are booked six weeks out, and you can't pressure wash anything because it won't dry before the rain bands arrive. We run storm prep between March and early May when humidity's still under 70% and surfaces actually cure after treatment.
Here's the schedule we follow for our Kiawah and Seabrook clients who don't want to be scrambling in August. Mid-March: full exterior wash (siding, decks, docks) while temperatures are in the 60s and things dry overnight. Early April: mildew treatment on north-facing walls and under eaves, then a week of dry weather to let the surfactant do its work. Late April: deck sealing and any exterior paint touch-ups. By May 15 you're weatherproofed before June 1 when hurricane season officially starts.
The logic's simple. Clean surfaces show you what actually needs fixing (rotted trim, cracked caulk, loose flashing) while you still have time to fix it. Sealed wood sheds water instead of soaking it up when the storm surge recedes. And if you do take a hit like we saw with Hurricane Helene in September 2024 (60-70 mph sustained winds across the Lowcountry), your post-storm cleanup is faster because you're not scrubbing six months of mildew on top of salt spray (National Weather Service Charleston).
One other thing: spring prep means your crew isn't working in 95-degree heat or dodging afternoon thunderstorms. We can take our time, catch details, and not rush because there's a tropical wave forming off the Cape Verde Islands. The houses that came through Helene cleanest were the ones we'd treated in April, not the ones we power-washed three days before landfall because that's when the owner finally called.
Frequently asked questions
Should I pressure wash before boarding up my house?
No. Wet siding won't dry before the storm hits, and you need every hour for actual prep (shutters, supplies, evacuation route). Schedule your wash in April or May instead, before hurricane season even starts.
How long after a hurricane can you pressure wash a house in Charleston?
Wait until power's back and you've photographed damage for insurance (usually 3-7 days). If you see heavy salt spray on siding, rinse it with a garden hose in the meantime so the stains don't set.
Can pressure washing damage storm-soaked wood?
Absolutely. Swollen wood splits and gouges under pressure. Let everything dry at least five days (longer if it was underwater or still feels soft).
What's the one thing I should clean before a Charleston hurricane hits?
Gutters and downspouts. Clogged gutters cause roof leaks and foundation flooding during a storm; dirty siding just sits there looking bad.
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