Most roof leaks start at a joint, not in the middle of the roof. Here is what each type of flashing does and how to tell when one has failed.
Flashing is the thin strip of metal or other waterproof material that turns water away from a joint on a roof: where the roof meets a wall, a chimney, a skylight or another roof slope. An apron flashing sits across the bottom of a wall or upstand and laps down over the roof; step flashings are short overlapping pieces that follow a sloping roof up the side of a wall; a counter (cap) flashing is tucked into the wall and laps over the base flashing below it; and valley flashing lines the channel where two slopes meet. Flashing works by overlap, not glue, which is why a wall-junction leak sealed only with silicone keeps coming back.
A roof sheds water well across its open surface. It leaks at the interruptions: where it meets a wall, goes round a chimney or a vent pipe, frames a skylight, or where two slopes meet in a valley. Flashing is the detail that bridges those joints. The Wikipedia summary defines it as thin pieces of impervious material installed to prevent water passing into a structure at a joint, and lists the usual materials: lead, aluminium, copper, stainless steel, zinc alloy and coated steels.
The key idea is overlap. A good flashing is lapped so that water running down the roof always lands on the next piece down, never behind it. Our awning joint guide puts it simply: a flashing sheds water by overlap, so sealant only protects its top edge.
| Type | Where it goes | How it works |
|---|---|---|
| Apron flashing | Across the bottom of a wall, chimney or dormer that rises out of the roof slope | One long piece dressed up the wall and down over the roof covering |
| Step flashing (soakers) | Up the side of a wall where a sloping roof runs alongside it | Short pieces that overlap each other in steps, one under each course of tiles or sheets |
| Counter (cap) flashing | Above a base or step flashing | Built into or tucked into the wall and lapped down over the base flashing, which can then be replaced |
| Valley flashing | In the valley where two roof slopes meet | A channel lining that carries the concentrated run-off |
| Kickout flashing | At the very bottom of a roof-to-wall junction | The last step piece, shaped to throw water away from the wall |
| Drip edge and cap flashing | At roof edges, and above windows and doors | Throws water clear of the face below |
The apron is the flashing you see as a band across the base of a wall, a chimney or the front of a dormer. Wikipedia notes the term goes back to strips of lead used to flash an edge, and is still used for the piece below a chimney. On Malaysian houses it is most common where a single-storey roof, such as a kitchen extension or porch, runs up to the face of a two-storey wall. Its top edge must be protected, either tucked into the wall or covered by a counter flashing, otherwise water runs down the wall behind it.
Where a sloping roof runs alongside a wall, one long strip cannot follow the slope and still sit under each tile. Step flashing solves this with short pieces, called soakers in some countries, that overlap each other in steps up the slope, one per course of tiles. Each piece turns up the wall and lies under the tile above. At the very bottom, a kickout piece throws the water out and away from the wall, so it does not run into the wall below the roof line.
Counter flashing is the second layer. The base or step flashing turns up the wall; the counter flashing is let into a groove in the wall, called a reglet, or built into the brickwork, and laps down over the top of the base flashing. The two parts can then move separately, and the base flashing can be replaced without breaking out the wall. Where a wall junction has only one piece, stuck to the plaster with sealant, there is no counter flashing, and the joint depends entirely on the sealant.
A valley carries the water from two slopes, so it is the busiest joint on the roof. Our valley flashing guide explains why a failed valley is a strip-and-rebuild job rather than a clean-and-seal. Chimneys, vent pipes, skylights and solar mounting points all need their own flashing detail; skylight edges are covered in our skylight leak guide.
Flashing can be lead, aluminium, copper, stainless steel, zinc or coated steel, and in repairs you also see bitumen-backed tapes. The Wikipedia article flags two practical rules. First, mixed metals can react: copper and lead should not be used in contact with, or above, aluminium, zinc or coated steel, because of galvanic corrosion. Second, aluminium is damaged by wet mortar and plaster. Long metal runs also need to allow for expansion.
Tape is a temporary patch, not a flashing. Our bitumen flashing tape guide explains when it helps and when it only hides the problem.
Inside, the signs are a stain along the line of an external wall, damp that appears only when rain comes from one direction, or water that shows up below a roof-to-wall junction. Our heavy-rain roof leak guide helps separate these from other causes.
Flashing repairs are priced per job, not per sq ft, and the range depends on length, access and what is found behind the old flashing. These are the ranges published on ClickBina guides:
| Work | Indicative price | Notes |
|---|---|---|
| Leak detection and assessment | RM300 – RM800 per visit | ClickBina price; charged separately from the repair |
| Roof-to-wall junction and flashing repairs | RM500 – RM3,000 per job | Market estimate; from reseal to full re-flash of a long run |
| Valley replacement with related tiling | RM800 – RM2,000 per job | Market estimate; driven by valley length and what is found |
WhatsApp us your job details for a quote — we reply within the hour.
💬 WhatsApp for a quoteWhere the stain and the junction are not obviously connected, the assessment is what stops you paying for the wrong repair. See our leak detection guide.
Roof-to-wall leaks often need several trades at once: the flashing itself, cutting a groove in the wall and making good, and sometimes a coating on the wall above. ClickBina is an experienced KL & Selangor contractor that handles whole-house refurbishment and coordinates the trades on one job. WhatsApp us your job details for a quote: where the roof meets the wall, which room shows the stain and when it leaks. We reply within the hour, the price we agree is a flat price with no hidden charges, and a site visit is RM150, waived if you go ahead.
How we estimated prices: every RM figure is quoted unchanged from the ClickBina guides named above; market ranges are typical Klang Valley figures for 2026, not fixed rates.
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