A damp patch under the window after rain? Find out whether the ledge, the window, the pipe hole or the aircon is to blame.
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When water comes into a room from the aircon ledge, it is usually one of four things: a blocked ledge outlet that lets rain pond against the wall, cracked or missing waterproofing on the ledge itself, a failed joint where the ledge meets the wall, window frame or pipe sleeve, or condensate pipes emptying onto the ledge. Watch when it leaks: only in heavy rain points to the ledge, the wall or the window; on dry days while the aircon runs points to condensate. Clearing the outlet is cheap; re-waterproofing a ledge uses membranes at RM6 – RM18 per sq ft supply and apply (indicative 2026, Klang Valley).
An aircon ledge is a small concrete shelf outside the window where the outdoor units sit. It is open to the rain, it collects condensate from any indoor-unit drain pipe that ends there, and it gathers leaves and bird droppings. ClickBina's aircon ledge guide puts it simply: a ledge needs its own outlet that is kept clear, and a blocked outlet ponds water against the wall.
The ledge sits right at the most leak-prone part of a facade: the junction of a slab edge, a wall, a window frame and a hole for the aircon pipes. Water that sits on the ledge for hours finds any crack or gap in that junction and tracks inwards. Inside, it shows up as a damp patch below the window, wet skirting, bubbling paint, or water running down the wall around the pipe hole.
| Cause | What you see inside | When it leaks |
|---|---|---|
| Blocked ledge outlet, water ponding | Damp patch below the window, wet skirting | During and after heavy rain |
| Cracked or failed ledge waterproofing | Damp spreading from the wall base under the ledge | After rain, slow to dry out |
| Ledge-to-window or ledge-to-wall joint | Water at the window corners or along the sill | Wind-driven rain |
| Pipe sleeve through the wall | Water around the aircon pipe hole or trunking | Rain, sometimes condensate |
| Condensate pipe emptying onto the ledge | Damp near the ledge even on dry days | While the aircon is running |
| Indoor unit itself leaking | Drips from the indoor unit or wall below it | While the aircon is running |
The last row is not a ledge problem at all. If water drips from the indoor unit, start with ClickBina's aircon leaking water guide; a blocked condensate line is the most common cause there.
Most ledges have a small outlet or a pipe through the edge to let water off. Leaves, sand, bird droppings and the grime washed off outdoor units block it, and the ledge becomes a shallow tray. Even when the outlet is clear, a ledge laid flat or sloping back towards the wall holds water against the wall base.
Clearing the outlet and keeping the ledge free of stored items costs very little and fixes a surprising number of leaks. If water still sits on the ledge after rain stops, the fall is wrong, and the surface has to be re-screeded to fall towards the outlet before it is waterproofed again.
Many ledges were finished with plain cement render and paint, or with a thin coating that has cracked as the slab edge moves in the sun. Water then soaks into the concrete and comes through at the wall base inside. The repair is the same logic as a small balcony: strip the failed surface, correct the fall, apply a membrane that turns up the wall and over the edge, and detail it around the outlet and the unit brackets.
ClickBina's balcony waterproofing guide compares the membranes used on open decks. On a ledge an exposed-grade liquid membrane is common, because it can be applied around brackets and pipes without joints.
Water also gets in where the ledge meets something else. The sealant along the window frame cracks, weep holes in the frame block, and the gap around the pipe sleeve opens up. These leaks often appear only in wind-driven rain, which is why they come and go.
If the water appears at the window corners, read ClickBina's window leak repair guide. If it appears around the pipe hole, the aircon wall-hole leak guide explains why trunking is not a weather seal and how the sleeve should be sealed from outside.
An indoor unit produces condensate whenever it cools, and its drain pipe has to take that water somewhere. In many condos the pipe simply ends on the ledge. On a ledge with a clear outlet and sound waterproofing that is harmless; on a ledge with a blocked outlet or cracked surface, the aircon feeds the leak every day, even without rain.
The fix is to run the condensate pipe to the outlet or the building's drain point rather than leaving it to spill across the ledge. Check the building's house rules on condensate routing too; water dripping onto another unit is a common complaint.
Testing one area at a time matters. Hosing the whole ledge, window and wall at once proves only that water gets in, not where.
In a strata building the external walls and the facade are generally common property, and ClickBina's common property leak guide lists facade cracks and failed joints as typical common-property sources. Aircon ledges are a grey area: some are within the parcel, others are part of the building's common property, and most buildings have their own rules on ledges and outdoor units.
Before paying for a repair, check the strata plan and the house rules, and report the leak to the management office in writing. A blocked outlet caused by your own stored items or condensate pipe is usually yours to fix; a cracked facade or a ledge that is common property is the management body's to repair.
High-floor ledges are an access question as much as a waterproofing one. If the ledge can only be reached from outside the building, the method and price change, so say which floor you are on when you ask for a quote.
These indicative Klang Valley figures (2026) are ClickBina's published ranges for the work an aircon-ledge leak usually needs:
| Work | Indicative price | Source guide |
|---|---|---|
| Leak detection and assessment (ClickBina, charged separately) | RM300 – RM800 per visit | Aircon wall-hole leak guide |
| Waterproofing membrane, supply and apply | RM6 – RM18 per sq ft | Balcony waterproofing guide |
| Acrylic coating on a wall face | RM4 – RM10 per sq ft | Aircon wall-hole leak guide |
| PU injection where masonry is cracked (market rate) | RM80 – RM250 per point | Aircon wall-hole leak guide |
| Clear and test window weep holes | RM100 – RM250 | Window leak repair guide |
| Full window perimeter re-seal | RM150 – RM600 per window | Window leak repair guide |
| Wall crack repair and re-coat above a window | RM500 – RM1,800 | Window leak repair guide |
WhatsApp us your job details for a quote — we reply within the hour. We serve KL, Selangor & Putrajaya.
💬 WhatsApp for a quoteA ledge is small, so the membrane itself is rarely the big number. Access, hacking a failed screed and making good the wall inside usually decide the final price.
ClickBina is an experienced KL & Selangor contractor for waterproofing and leak repairs. WhatsApp us your job details for a quote and tell us when the leak appears. We reply within the hour, and the price we agree is a flat price with no hidden charges. Where the source is not obvious, leak detection and assessment is a separate paid service.
How we estimated prices: every RM figure on this page is quoted unchanged from the ClickBina guide named beside it, where it is an indicative 2026 range for the Klang Valley. Responsibility depends on your building's strata plan and house rules; this is general information, not legal advice.
WhatsApp us your job details for a quote — we reply within the hour. We serve KL, Selangor & Putrajaya.
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