Siding is not waterproof. It is a rainscreen, designed to shed most water and let the rest drain out behind it. That system works because water always travels downward and outward.
A pressure washer aimed upward under the laps reverses that. It pushes water sideways and up into a cavity that has no way to drain it.
Once water is behind the wall, the clock starts. Wet building materials can begin supporting mould growth within roughly 24 to 48 hours under the right conditions.
Do the following first. Read the explanation afterwards.
Do These Things Now
- Stop the water. If a wash is in progress, stop it. Do not wait for the crew to finish the elevation.
- Treat electrical as a hazard until proven otherwise. If there is water near outlets, switches, exterior fixtures or a panel, or if a GFCI has tripped, do not reset it and do not touch wet fixtures. Turn off the affected circuit at the panel only if you can do so safely and dryly, then call a licensed electrician. Connecticut licenses electrical work and you can verify at eLicense.ct.gov. This is not a DIY item.
- Photograph and video everything before you move or dry anything. Interior and exterior, wide and close, with timestamps. This is the step people skip and regret. Capture the wall, the ceiling below, the window, the exterior elevation directly outside, and the weather that day.
- Move what is at risk. Furniture, rugs, electronics, boxes, anything stored against that wall.
- Get air moving. Open the space, run fans and a dehumidifier if you have one. Do not point a heater at a wet wall. Warm, damp, still air is exactly what mould wants.
- Do not close the wall back up or paint over a stain. Trapping moisture behind a repair is how a small event becomes a large one.
- Notify the contractor in writing immediately. Email or text so it is timestamped. Facts only, no accusations yet.
- Call your insurer’s claims line to ask about the process before you authorise repair work. Ask specifically what documentation they will want and whether an adjuster needs to see it before it is opened up.
- Find the source. Water in a wall came from somewhere specific. The diagnostic walk is below.
- If the wet area is more than a small patch, call a water damage restoration professional. Firms working to IICRC S500 standards have moisture meters and thermal imaging that will find how far the wetting has travelled inside the wall. You cannot determine that by looking.
The two things that cost homeowners most in these situations are resetting a tripped breaker on a wet circuit, and closing a wall back up before it is dry. Do neither.
If you need a second opinion on where the water came in, we will walk the elevation with you. Call Roman at (860) 263-9031.
Why the First 48 Hours Matter
Under favourable conditions, wet porous building materials such as insulation, drywall, OSB sheathing, framing lumber and paper facings can begin supporting mould growth within roughly 24 to 48 hours, according to EPA and IICRC guidance. The water event itself is usually small. The delay in drying is what makes it expensive.
A few material-specific notes worth knowing:
- Fibreglass insulation does not rot, but it holds water against the sheathing and takes a very long time to dry inside a closed cavity.
- Wet OSB swells, loses strength and does not fully recover. This is the material most modern sheathing is made from.
- Cellulose and mineral wool behave differently again, which is one reason a professional with a moisture meter is worth the call.
For guidance on mould specifically, EPA and the Connecticut Department of Public Health are the right sources. This article cannot and does not tell you whether you have a mould problem or what it means for your health.
How Water Gets Behind Siding in the First Place
Now that you have acted, here is the mechanism.
Spraying upward under the laps
This is the overwhelming cause.
Siding laps shed water downward. Water directed up under a lap goes behind the drainage plane, above the weep holes, with nowhere to exit.
Correct technique on any lap siding is down and across, never up. That single rule prevents the large majority of these events.
High pressure at close range
Force pushes water through joints, seams, butt joints, corner posts, J-channel and around penetrations that handle ordinary rainfall perfectly well.
Spraying directly at penetrations and openings
Window and door heads, dryer vents, exhaust hoods, hose bibs, electrical penetrations, cable entries, AC line sets. Every one of these is sealed against rain falling down, not against water driven sideways under pressure.
Pre-existing defects the wash simply found
This one deserves honesty, because it is genuinely common on older Central Connecticut homes.
- Missing or reversed head flashing above windows and doors
- Missing kick-out flashing where a roof edge meets a wall, which diverts runoff into the gutter instead of behind the siding — an extremely common defect and a classic source of hidden rot
- Failed caulk at trim, corners and penetrations
- No weather-resistive barrier at all behind the siding, which we see regularly where 1970s and 80s aluminum or vinyl went straight over original wood siding
- Weep holes blocked or painted shut
- Deteriorated seals on original window units
On older homes, a wash frequently reveals a defect rather than creating one. That does not make poor technique acceptable. It does change the repair conversation, and it changes who pays.
Open windows and the obvious
Worth stating plainly: confirming that windows are closed and latched is part of a professional pre-wash walkthrough. Storm windows and older double-hungs leak readily, and nobody should be finding that out mid-job.
Find the Source: A Diagnostic Walk
- Map the wet spot to the exterior. Go outside and stand at the exact corresponding point. What is directly above it? A window, a roof-wall junction, a vent, a light fixture?
- Remember that water travels down and sideways. The entry point is almost always above the visible damage, sometimes by several feet.
- Check the window and door heads on that elevation for flashing and caulk condition.
- Check every roof-to-wall junction on that elevation for a kick-out flashing at the bottom of the roof edge. If there is not one, you have very likely found a long-standing defect that predates any wash.
- Check the weep holes at the bottom of the siding courses. Clear, or painted shut?
- Check the soffit and fascia above for dripping.
- Consider what is inside that wall. A bathroom, kitchen or laundry wall complicates the picture, because the source may be plumbing that the wash simply coincided with. It happens.
- Run the hose test. After everything is dry, have someone gently run a garden hose with no pressure on specific areas one at a time, starting low and working upward, while you watch from inside. This is a standard diagnostic method and it isolates the entry point without causing further harm.
Who’s Responsible? The Connecticut Picture
General information about the process in Connecticut, not legal or insurance advice. Coverage varies by policy, so speak to your agent and, for anything substantial, an attorney.
There are three possible answers, and the diagnostic determines which one applies.
| Scenario | Who typically pays |
|---|---|
| The contractor’s technique caused it | Pursued against their general liability policy |
| A pre-existing defect caused it and the wash exposed it | Homeowner’s repair, though technique may be a contributing factor |
| Both | The most common real-world outcome, and where an independent written opinion matters most |
The steps:
- Request the contractor’s certificate of insurance and the carrier’s claim contact
- Verify HIC registration at eLicense.ct.gov. Residential home improvement work in Connecticut requires registration with CT DCP under the Home Improvement Act (CGS Chapter 400), and the HIC number must appear on contracts and advertising
- Get an independent assessment from a home inspector, building envelope consultant or restoration professional, with photos and a written opinion on cause
- Notify in writing, attach the documentation, state what you are seeking, and set a reasonable deadline
- On your own policy: sudden and accidental water discharge is often covered, while gradual leakage, seepage and long-term moisture damage commonly are not. Mould coverage is frequently limited or capped. Call your agent rather than assuming
- If unresolved: complaint to CT DCP, the Home Improvement Guaranty Fund for registered contractors, Small Claims up to $5,000, Superior Court above that
What Proper Repair Looks Like
So nobody talks you into either too little or too much.
- Dry it before you close it. Documented moisture readings, not somebody’s opinion that it looks dry.
- Open the wall where needed. Interior drywall removal is often the fastest and least destructive route to drying a cavity properly.
- Wet fibreglass insulation in a closed cavity generally gets replaced, not dried in place.
- Fix the actual defect. Flashing, kick-out, caulk, weep holes. Not just the stain on the drywall.
- Photograph every stage, for insurance and for resale disclosure later.
- On a pre-1978 home, repair work disturbing painted surfaces falls under the EPA Lead RRP Rule and should go to a lead-safe certified firm.
- Permits. Depending on scope, repairs may require a permit through the Town of Newington Building Department.
- Keep everything for the file. Connecticut sellers of one-to-four-unit residential property are generally required to provide a Residential Property Condition Disclosure Report, and documented, properly repaired water damage is a far better disclosure than an unexplained stain. Confirm current requirements with CT DCP.
To be clear about our role: Mr-Suds does not perform water damage restoration, mould remediation, electrical work or flashing repair. Those are separate trades and we refer them out.
How a House Should Be Washed So This Never Happens
This is the checklist to hold any contractor to, including us.
- Cold water, low pressure, chemistry doing the work
- Down and across the laps. Never up
- Windows and doors checked closed and latched during the pre-wash walkthrough
- Vents, fixtures, outlets, AC units and penetrations covered or avoided
- Distance and angle maintained, with no close-range blasting at seams or trim
- Older homes and unknown wall assemblies treated more conservatively, not less
- A pre-wash walkthrough that identifies existing defects such as missing kick-outs, failed caulk and deteriorated trim, and flags them in writing before work starts
- A post-wash walkthrough with the homeowner before anyone packs up
- Owner-supervised work, so pressure and technique decisions are not being made by whoever happens to be holding the wand
That pre-wash walkthrough protects both parties, and I want to be straight about that. It tells you what was already wrong with your house. It also tells me, in writing, what I did not cause. On older homes in Newington and Wethersfield, we have flagged missing kick-out flashings and rotted window trim on more than a few walkthroughs and declined to wash that elevation until it was addressed. Nobody enjoys that conversation. Everybody prefers it to the alternative.
One practical note on paperwork. A registered, insured contractor invoicing with the 6.35% Connecticut sales tax on residential maintenance services, per CT DRS, is also the contractor who actually carries liability if something goes wrong. A cash job with no paperwork has no recourse behind it at all.
FAQs
Can pressure washing force water inside a wall? Yes, particularly when spray is directed upward under the siding laps or at close range into seams and penetrations.
How long before mould grows in a wet wall? EPA guidance indicates wet materials can begin supporting growth within roughly 24 to 48 hours under favourable conditions. Drying quickly is what matters.
How do I know if water is still in the wall? A moisture meter and thermal imaging, used by a professional. Visual inspection is unreliable and a dry-looking surface tells you very little.
Does homeowners insurance cover water damage from a pressure washer? Damage caused by a contractor is usually pursued against their liability policy. Coverage on your own policy varies, so call your agent.
Should I open the wall up? Often it is necessary to dry the cavity properly. Document everything first, and check with your insurer before you start.
What is a kick-out flashing and why does it matter? It is a small piece of flashing at the bottom of a roof edge where it meets a wall, which diverts runoff into the gutter instead of behind the siding. Missing kick-outs are a very common source of hidden wall rot.
How can I tell if the washer caused it or it was already a defect? Run the diagnostic walk above, then get an independent written assessment. Both scenarios are common and the answer is often some of each.
How should a house be washed to prevent this? Cold water, low pressure, sprayed down and across, windows closed and checked, penetrations protected, and a pre-wash walkthrough before anyone starts.
Get a Pre-Wash Walkthrough That Finds Problems First
The Walkthrough Happens Before the Wash, Not After
Every Mr-Suds job starts with a walkthrough that identifies existing flashing, caulk and trim defects, and finishes with a walkthrough together before we leave. Cold water, low pressure, downward only, on every siding job.
If your house has a problem we should not wash over, you will hear it at the estimate.
See our house washing service, what soft washing actually is, pressure washing services in Hartford for the surfaces where high pressure is correct, real before and after results, and what homeowners say in our reviews.
Get a Free Quote or call (860) 263-9031
Veteran owned. Licensed, bonded and insured. HIC registered. Owner-supervised on every job. Serving Newington, Hartford, Wethersfield, Rocky Hill, Glastonbury and Central Connecticut.