Window leaking when it rains? The five entry paths, why silicone-over-silicone fails, sliding-door track fixes and who pays in a condo — with Klang Valley prices.
“My window leaks when it rains” is one of the most common WhatsApp messages we receive during monsoon months — and the glass is almost never the problem. A window is a hole cut in a waterproof wall, and everything depends on the joints around it: the perimeter sealant between frame and wall, the flashing under the sill, the drainage inside the frame, and the condition of the wall above. Each of those was installed once, years ago, and has been baking and flexing in Malaysian sun and storms ever since. When one gives way, water follows gravity and hidden cavities, often emerging far from where it entered — a wet carpet at the window, a stain at the ceiling corner, or paint bubbling half a metre below the sill. That is why window leaks resist DIY guesswork: the exit point you can see is rarely the entry point that needs fixing.
Nearly every rain-triggered window leak comes down to one of five paths — and correctly naming the path is most of the repair.
| Entry path | How the water gets in | Typical fix |
|---|---|---|
| Perimeter sealant failure | The frame–wall sealant cracks, peels or debonds, opening a slot straight into the wall | Cut out old sealant fully and re-seal (RM150–RM600/window) |
| Blocked weep holes | Frame drainage slots clog with dirt or paint, so the frame fills and overflows inward | Clear and test the weep holes; re-form if sealed over |
| Sill flashing failure | Missing or corroded flashing lets water under the frame at the sill line | Re-flash the sill; re-form the drip groove |
| Wall crack above the window | Hairline cracks feed water into the cavity, which drains onto the frame head | Crack repair plus elastomeric re-coating of the wall zone |
| Aluminium frame joints | Mitred corner and mullion joints open with age, leaking inside the frame itself | Seal frame joints internally; renew gaskets |
Klang Valley thunderstorms do not drop rain vertically — squall winds drive it horizontally against facades, and the pressure difference across the wall physically pushes water through gaps it would never enter in calm drizzle. Wind pressure can force water uphill over a sill, past a lazy sealant joint and through weep holes that normally drain outward. That is why a window can stay bone-dry through a week of light rain and then flood during one evening storm, and why hose-testing a suspect window on a calm day can miss the fault entirely unless the test mimics pressure from the right direction. Upper floors and corner units take the worst of it: wind speed and exposure rise with height, which is one reason high-rise window leaks are so persistent.
A proper diagnosis runs top-down in the wall but bottom-up in the test. Start with inspection: sealant condition around the full perimeter, weep holes clear or clogged, sill flashing and drip groove present, cracks in the wall above, and the state of the frame’s corner joints. Then hose-test in stages, lowest element first — sill zone, then frame, then the wall above — waiting between stages, because testing everything at once tells you nothing about which path leaked. Indoors, note exactly where water first appears and when: within minutes of rain suggests sealant or weep holes; an hour later and spreading from above suggests the wall is feeding the frame from a crack you have not found yet. We photograph each stage so the repair quote maps to evidence, not guesswork — the discipline that separates a lasting fix from the third re-silicone this year.
Here is the uncomfortable truth about the most common “fix”: smearing new silicone over old silicone almost always fails. New sealant cannot bond to a degraded, chalky, dirt-filmed surface; the old bead underneath keeps debonding at its original failure line; and doubling the thickness robs the joint of the movement capacity it needs as the frame expands and contracts. Done properly, re-sealing means cutting the old bead out completely, grinding and cleaning the joint faces, priming where the substrate demands it, installing backer rod so the new bead has the right depth-to-width shape, and gunning a neutral-cure silicone or polyurethane sealant rated for facade movement. At RM150–RM600 per window (indicative 2026, Klang Valley), a properly re-built joint lasts years; a cosmetic over-smear typically fails at the next monsoon and adds a layer that makes the eventual proper job harder.
Aluminium window frames are designed to leak — inward capture, outward drain. Water that gets past the outer gasket collects in the frame’s bottom channel and escapes through small weep holes on the outside face. Painters, well-meaning owners and years of grime routinely seal these shut, and a frame that cannot drain fills like a bathtub until it overflows onto your sill. Checking them is genuinely DIY territory: find the slots on the outside bottom of the frame, confirm they are open with a soft wire or a puff from a straw, and pour a small cup of water into the bottom track to watch it drain out. If someone has siliconed the weep holes closed — a mistake we find weekly — they must be cut open again. Never seal a weep hole to “stop a leak”; you are disabling the drainage that prevents one.
Two paths hide outside the frame entirely. Under the frame, the sill flashing — and the drip groove on the concrete sill nose — exists to throw water clear; when the flashing is missing, corroded or bridged by render, water tracks along the underside of the sill and into the wall below the window. Above the frame, hairline cracks in the render feed rainwater into the wall, where it drains down the cavity and appears at the window head as if the window itself failed. The fix above is crack repair — routed and sealed, or pressure-grouted with PU resin for deeper, actively weeping cracks, as covered in our PU injection guide — followed by an elastomeric re-coat of the wall zone so the next hairline crack is bridged before it leaks. Our wall waterproofing guide covers those coatings in detail, and our grouting vs waterproofing guide explains which injection method suits which crack.
Balcony sliding doors are the window leak’s bigger sibling. The track sits at floor level, directly in the path of wind-blown rain and balcony wash-down water, relying on tiny track drains and a thin flashing line under the frame. When storms flood the track faster than it drains — or the flashing under the track has corroded — water sheets over the interior lip and across the floor, sometimes reaching the downstairs unit’s ceiling. Quick wins include clearing the track drains and renewing perished roller seals, but a track that leaks in every major storm usually needs to be lifted and re-flashed: frame out, new flashing and upstand detail formed under the track, frame re-bedded and re-sealed. Expect RM800–RM2,500 per door (indicative 2026, Klang Valley) depending on width and access — and if the balcony floor itself is suspect, address it together with the door.
| Repair | Indicative cost (2026, Klang Valley) | Notes |
|---|---|---|
| Clear & test weep holes, minor track service | RM100 – RM250 | Often bundled into a diagnosis visit |
| Full perimeter re-seal (cut out & re-bed) | RM150 – RM600 / window | Size, floor height & access drive the range |
| Frame joint & gasket resealing | RM200 – RM500 / window | For aged aluminium corner and mullion joints |
| Wall crack repair & elastomeric re-coat above window | RM500 – RM1,800 | Includes PU injection where cracks weep actively |
| Sliding-door track lift & re-flash | RM800 – RM2,500 | Frame out, new flashing & upstand, re-seal |
High external access — gondola, rope access or scaffolding on upper floors — can add meaningfully to any of these figures, which is one more reason condo external repairs usually route through management. For multi-window facades it is often cheaper per window to re-seal a whole elevation in one mobilisation; our waterproofing contractor guide explains how to compare quotes for that kind of scope.
In a stratified building, where the leak enters decides who repairs it. The external facade — outer walls, curtain wall panels, external sealant lines and flashings — is generally common property, which makes it the management’s (JMB/MC’s) responsibility to maintain, while the window unit itself and internal finishes are typically yours. In practice: document the leak with photos and video during rain, report it to management in writing, and push for a joint inspection before commissioning your own external works — paying a contractor to abseil down common property without approval can leave you out of pocket and out of warranty. Curtain-wall buildings are a special case: their gasket-and-drainage systems need specialist facade contractors, not a tube of silicone from level 23. The full ownership and evidence playbook is in our external wall seepage guide.
ClickBina repairs rain-triggered window and sliding-door leaks across the Klang Valley the methodical way: staged inspection and hose testing to name the entry path, then the matching fix — full-perimeter re-sealing, weep-hole restoration, sill re-flashing, wall crack injection and re-coating, or a sliding-door track lift and re-flash — with itemised quotes and photos at every stage. We work with owners, tenants and building management alike, and we will tell you honestly when a leak is the management’s facade problem rather than your window. WhatsApp us a photo — or better, a 10-second video taken during the rain — and we will usually name the likely entry path within the hour.
Tell us what you need — we reply within the hour.