A stain right under where a pipe goes through the roof is one of the most common roof leaks. Here is why it happens and how it should be fixed.
Every pipe, vent or cable that passes through a roof needs its own flashing, usually a rubber pipe boot or a metal collar lapped under the roofing above and over it below; when a leak appears under a pipe, the cause is almost always a missing boot, a boot cracked by sun, a tile or sheet cut and left open, or a bead of sealant doing a flashing's job. Leaks that start soon after an aircon, water heater or solar installation usually trace back to the new hole. On ClickBina's guides, roof junction and flashing repairs sit at RM500 – RM3,000 per job, and ClickBina leak detection is RM300 – RM800 per visit, charged separately.
A penetration is any place where something passes through the roof covering: a plumbing vent stack, an aircon refrigerant pipe run to a unit on the roof, the hot and cold pipes of a solar water heater, cables from solar panels, an exhaust duct, or the fixing of an antenna or satellite dish. Each one breaks the continuous surface that sheds rain.
Wikipedia's flashing entry describes flashing as thin pieces of impervious material installed to stop water passing into a structure at a joint, and names vent pipes among the objects it protects. It lists pipe flashing, also called a pipe boot, vent boot or pipe flange, as the product used where pipes penetrate roofs.
Many of these were added years after the house was built, by trades whose main job was not roofing. That is why penetrations are among the most common leak points on older roofs.
| Roof type | Proper detail at a pipe | Common shortcut that leaks |
|---|---|---|
| Clay or concrete tile | Lead or flexible flashing dressed to the tile profile, lapped under the course above | Tile cut around the pipe and the gap filled with mortar or sealant |
| Metal deck | Rubber pipe boot with a flexible base, screwed and sealed to the sheet profile | Hole cut and pipe sealed with silicone only |
| Flat concrete roof | Pipe sleeve cast or sealed in, with membrane taken up the pipe and clamped | Membrane stopped short and the joint painted over |
| Any roof, cables | Proper cable entry gland or conduit boot | Cable pushed through a lifted tile or a drilled hole |
The principle is the same on every roof: water running down the roof must meet a flashing that is lapped under the covering above the pipe and over the covering below it, so the water is carried round and past the hole. Sealant has a role in the detail, but it cannot replace the lap.
Wikipedia's flashing entry notes that flexible flashing products include rubberised asphalt, butyl rubber and acrylic, each with different adhesion and temperature limits, which is why the material has to suit both the roof and the pipe.
If a ceiling stain appears within weeks of new equipment going on the roof, start with the new work. Installers often run pipes through the roof by the shortest route, lift or break tiles to get there, and seal the gap with whatever they have. ClickBina's solar roof leak guide covers the solar side in detail; the same questions apply to aircon and water heater pipes: where did the pipe go through, what was used to seal it, and were any tiles cracked on the way.
Keep the installer's details and ask them to inspect first, but judge the repair on whether it gives the pipe a real flashing, not on whether the stain stops for a week.
If the stain is not directly under a penetration, the cause may be elsewhere, such as a valley, a ridge or a wall junction. ClickBina's roof flashing guide explains the other junctions that fail.
On a tiled roof the pipe usually passes between or through tiles. The proper fix lifts the tiles around it, fits a flashing shaped to the tile profile and laps it correctly, then relays or replaces the tiles. Cracked tiles nearby are replaced at the same time, because installers' feet often break more than one.
On a metal deck the standard part is a flexible rubber pipe boot. Its base is pressed to the sheet profile, screwed and sealed, and the collar is cut to grip the pipe. Boots must suit the pipe size and the heat of the pipe; a boot that is too small tears, and one that is too large leaves a gap. Rusted sheet around an old hole may need a patch or sheet replacement first. ClickBina's metal roof leak guide covers the other failure points on a metal deck.
On an RC flat roof, the waterproofing membrane has to be carried up the pipe and clamped or sealed to it, with a proper upstand, not stopped at the slab. Where several pipes cluster, a raised kerb or a pipe box around them is easier to waterproof than many separate collars.
Indicative Klang Valley figures from ClickBina's published guides (2026).
| Item | Indicative price | Source guide |
|---|---|---|
| ClickBina leak detection and assessment (per visit) | RM300 – RM800 | Roof flashing guide |
| Roof-to-wall junction and flashing repairs (per job) | RM500 – RM3,000 | Roof flashing guide |
| Tiled or metal roof repairs at penetrations (per job) | RM500 – RM3,000 | Solar roof leak guide |
| Replace cracked or broken tiles | RM600 – RM2,500 | Roof repair cost guide |
WhatsApp us your job details for a quote — we reply within the hour.
💬 WhatsApp for a quoteLeak detection is charged separately from the repair. Ceiling repairs and repainting below the leak are quoted with the job.
WhatsApp us your job details for a quote: where the stain is, which pipes or equipment pass through the roof above it, and when the equipment was installed. ClickBina leak detection is RM300 – RM800 per visit, charged separately, and pinpoints the source before any tiles or sheets come off. ClickBina is an experienced KL & Selangor contractor for whole-house refurbishment and trade coordination, so ceiling repairs below the leak can be handled together. 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 on this page is quoted unchanged from the ClickBina guides named above; they are indicative Klang Valley ranges for 2026, not fixed rates or a price for your roof.
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