What is commercial window and facade waterproofing?
It's the repair of the parts of an exterior wall that keep rain out: the sealant joints around windows and between panels, the flashings at window heads and sills, the weather-resistive barrier behind the cladding, and the cladding itself. On commercial and multi-family buildings that might be brick veneer, EIFS (synthetic stucco), fiber cement, metal panels, concrete or a mix of them, with punched windows set into each.
Modern walls don't rely on the outer surface being perfect. They're built in layers: cladding sheds most water, a drainage gap and barrier behind it catch what gets through, and flashings send that water back out at every window, floor line and base of wall. Facade leaks happen when one of those layers is missing, blocked or broken. The job is to find which one, then restore it so the wall drains again.
This page covers windows set into a wall and the wall around them. Large framed glass systems, such as storefronts and curtain walls, are a different kind of assembly, covered under curtain wall and storefront leak repair.
How are window and wall leaks found and fixed?
Water testing from the bottom up
The most reliable way to find a facade leak is a controlled water test. A calibrated spray rack or nozzle wets one component at a time, starting low and working up. First the sill, then the jambs, then the head, then the wall above. Someone watches inside for water. Starting at the bottom matters: if you wet the top first, water running down could trigger a leak lower on the wall and confuse the result. On larger projects, field testing follows procedures from industry standards such as ASTM E1105 for windows.
Opening the wall where needed
When the water test points to a hidden flashing, a small exploratory opening is cut in the cladding to see the barrier and flashing directly. It's patched afterward. One look often settles what hours of guessing can't.
Typical repairs
- Sealant joint replacement. Old sealant is cut out completely, the joint is cleaned and primed, then backer rod and new sealant go in with the right joint profile.
- Sill and head flashing. Windows missing sill pans or end dams are removed and reset with proper flashing, or flashed from outside where full removal isn't practical.
- Weep restoration. Blocked weeps in brick veneer and window frames are cleared so water can drain out.
- Cladding repairs. Cracked EIFS, open panel joints and failed siding transitions are repaired and tied back into the barrier behind them.
What are the warning signs of a window or facade leak?
- Damp or stained drywall below the corners of a window.
- Leaks that appear only during wind-driven rain from one direction.
- Cracked, shrunken or pulled-away sealant around window frames and panel joints.
- Swollen, soft or rotting interior window sills and stools.
- Efflorescence, damp patches or moss on brick below windows.
- Cracks or bulges in EIFS, especially at window corners.
- Musty smells or mold on the inside face of exterior walls.
- Peeling paint or bubbling finishes on window returns.
What causes facade and window leaks?
- Sealant at end of life. Joint sealants lose elasticity with sun and movement and start to crack or pull away. Joints installed without backer rod, or bonded on three sides, fail sooner.
- Missing sill flashing. Windows set without a sloped sill pan and end dams have nowhere to drain water that gets past the frame.
- Reverse laps. Barrier or flashing installed so the upper layer tucks behind the lower one channels water into the wall instead of out of it.
- Blocked drainage. Mortar droppings in brick cavities, painted-over weeps and sealant smeared over drainage paths trap water.
- Long wet seasons. Puget Sound rain lasts for days at a time. Walls that would dry between short storms elsewhere stay wet here, so small defects show up as leaks.
- Building movement. Settling, temperature swings and seismic movement crack rigid cladding and stress joints at floor lines.
What can you check safely before calling?
- Write down the wind direction and rain intensity each time the leak appears. One elevation leaking points to that face of the building.
- Check whether the water appears at the window corners, the sill, or above the window head.
- From the ground or a window, look for cracked or missing sealant around frames.
- Look for weep holes at the bottom of window frames and the base of brick walls, and whether they're blocked or painted over.
- Check gutters and roof edges above the area. Overflowing gutters can dump water onto a wall and window below.
Pro tip: test with a garden hose, carefully
If you can safely reach a ground-floor window, run a gentle hose on the sill alone for 10–15 minutes while someone watches inside, then the jambs, then the head. Never blast it with a pressure nozzle. That forces water in where rain wouldn't.
Warning: don't seal the weeps
Caulking every gap you can see, including weep holes and the bottom edge of window frames, traps water inside the wall and can make the leak worse.
What happens during the specialist's visit?
- Interview and interior checkWhere and when it leaks, what the wall is made of, and moisture readings around the wet area.
- Exterior surveySealant joints, flashings, weeps, cladding cracks, and roof edge or gutter conditions above.
- Water testComponent-by-component spray testing from the bottom up until the leak is reproduced.
- Exploratory opening if neededA small cut in the cladding to see the flashing or barrier directly.
- RepairSealant replacement, flashing correction, weep clearing or cladding repair at the confirmed source.
- Re-test and reportThe same water test is repeated to confirm it's dry, with photos and notes on similar windows.
What affects the cost of facade leak repair?
| Factor | Effect on the job |
|---|---|
| Access | Upper floors may need a lift, swing stage or scaffolding. |
| Testing scope | One window versus a full elevation investigation. |
| Cladding type | Matching EIFS, brick or custom panels takes skill and time. |
| Hidden damage | Wet sheathing or framing behind the cladding adds repair work. |
| Repeat conditions | A detail failing at one window often fails at similar ones. |
When is a wall leak urgent?
Most facade leaks are slow, but some can't wait. Call right away when water is running down a wall into electrical outlets or panels, when a window or panel has been damaged and is open to the weather, or when cladding is loose and could fall. A crew can board or tarp the opening and make it safe, then come back for testing and permanent repair. Use emergency commercial leak repair for those calls.
Loose cladding over walkways
Panels, stone or stucco that are bulging or loose above entries and sidewalks need the area below closed off until they're secured.
Window and facade FAQ
How often should exterior sealant joints be replaced?
It depends on the sealant, the sun exposure and the joint movement. Inspect them regularly, and plan replacement when they start cracking, hardening or pulling away, rather than waiting for leaks.
Can you just caulk the outside of the window?
Sometimes that's the right repair, if the perimeter sealant is what failed. But if the window has no sill flashing, or the barrier behind the cladding is lapped wrong, caulk only hides the problem for a while.
Why does only one side of the building leak?
Storms tend to come from a prevailing direction, so the wall facing them takes the most wind-driven rain. Defects on that elevation show up first, while identical defects on the sheltered side may never leak.
Is EIFS more likely to leak?
Older barrier-type EIFS has no drainage plane, so water that gets behind it stays there. Newer drainable systems handle small leaks better. Either way, sealant joints and window flashings are the usual weak points.
Do you need to remove the window to fix the leak?
Not always. Perimeter sealant and some flashing fixes can be done in place. If the window has no sill pan or the barrier is lapped wrong behind it, removing and resetting the window is often the only lasting fix.
Can leaks behind the wall cause mold?
Yes. Water trapped behind cladding and drywall can rot sheathing and grow mold before anything shows inside. That's one reason to investigate stains under windows promptly.
Related services and areas
Window and wall leaks are common in condo and HOA buildings on the Westhill side of town, and in office buildings around North Creek. Leaks right at the top of the wall usually belong to parapet and flashing repair. Not sure where your water comes from? Learn how specialists find and fix commercial leaks.