A stain along the wall you share with next door? Here is where the water gets in, whose side it is, and how to fix it once.
When a terrace house leaks along the line it shares with the next house, the water is usually getting in at one of four shared details: the top of the party wall, a valley or gutter between the two roofs, the joint where a neighbour's higher roof or extension meets yours, or a neighbour's gutter or downpipe emptying onto your side. Trace it before anyone repairs anything, because the fix may be on the neighbour's half. ClickBina's leak detection is RM300 – RM800 per visit, charged separately from the repair, and roof-to-wall junction and flashing repairs run RM500 – RM3,000 per job on ClickBina's guides (indicative 2026, Klang Valley). For ordinary wear and tear on a shared wall, ClickBina's party wall guide says both owners generally share the cost.
A terrace row is one long building split into separate titles. The roof looks continuous, but underneath it every house has its own tiles, battens, gutters and repairs history, and the joins between houses are where two different owners' work meets. After twenty or thirty years one owner has re-roofed, another has extended at the back, a third has raised a porch roof, and the line between two houses becomes a patchwork of materials that were never detailed to work together.
Water does not respect the title boundary. A defect on your neighbour's half can soak your ceiling, and a defect on yours can show up in their bedroom. That is why this kind of leak often survives several repairs: each owner patches their own side of a problem that sits exactly on the line.
ClickBina's roof flashing guide explains why the higher-roof junction is so often the culprit: a counter flashing let into the wall and lapped over the base flashing lets the two parts move separately, whereas a sealant-only junction cracks in the sun.
Where the stain appears, and when it drips, tells you a lot before anyone climbs up. Use this table as a first guide, not a diagnosis.
| What you see | Likely shared detail | Whose side to check first |
|---|---|---|
| Damp band running down the party wall from the ceiling | Party-wall top: cracked mortar or lifted flashing | Both; the defect may be on either half of the wall top |
| Ceiling stain along the wall only during heavy rain | Shared valley or box gutter overflowing | Both; overflow spills to whichever side is lower |
| Leak started after the neighbour built or raised a roof | Higher-roof junction or new discharge | Neighbour's new work first |
| Drips at the back of the house, near the kitchen extension | Extension roof joint to the party wall | Whoever built the extension |
| Water on the porch ceiling next to the shared wall | Porch roof flashing on the shared wall | Both porches |
| Stain keeps coming back after your own roof was repaired | The source is on the other half | Neighbour's half |
A stain far from the wall is less likely to be a shared detail. ClickBina's heavy-rain roof leak guide covers the leaks that only show in a downpour, and a leak that drips long after the rain has stopped may be something else entirely.
The most expensive mistake in a shared-roof leak is repairing the wrong half. Before paying for work, get the source found and recorded. A proper check looks at both sides of the line from above and from inside the roof space, tests the suspect gutter or valley with water, and records which side the water is coming from.
ClickBina's leak detection is priced separately from any repair, so the visit is paid for finding the leak, not for selling a particular fix. For a shared roof, ask for the findings in writing with the location marked, because that record is what you will show your neighbour.
Many shared-roof leaks start the rainy season after a neighbour's renovation: a raised roof, a new rear extension, a porch roof carried across to the party wall, or tiles disturbed while their contractor worked on the wall top. Signs that point that way are simple: the leak began soon after their works, it sits at the junction with their new roof, and your own roof has not changed.
ClickBina's party wall guide sets out the principle for damage caused by a neighbour's contractor: the owner who engaged the contractor is responsible for it. Keep dated notes of when the works happened and when the leak began.
For a landed terrace, the party wall guide explains that each owner owns the half of the party wall on their side, and that both adjoining owners share a right of support, so neither may weaken the wall. For repair costs it gives a simple rule of thumb:
These are general principles, not legal advice for a particular dispute. Where the amounts are large or the neighbour disputes the cause, the party wall guide is the place to start.
Most shared-roof leaks are settled over the fence, not in a tribunal. It helps to bring facts rather than blame: the date the leak started, where the stain is, and the written findings of the leak check. Propose one joint repair of the whole shared detail, with the cost split agreed before work starts.
Access matters too. Repairing a party-wall top or a shared valley usually means working from both roofs, and sometimes from the neighbour's roof space. Agree the dates, who will be home, and how the roof will be protected. Put the agreement, however short, in writing, a message both of you reply to is better than nothing.
The right repair depends on which detail failed. These are the related prices published on ClickBina's guides (indicative 2026, Klang Valley).
| Work | Indicative price | When it fits |
|---|---|---|
| Leak detection and assessment | RM300 – RM800 per visit | Finding which detail and which side; charged separately from the repair |
| Roof-to-wall junction and flashing repairs | RM500 – RM3,000 per job | Party-wall top or higher-roof junction, from reseal to full re-flash |
| Valley replacement with related tiling | RM800 – RM2,000 per job | Shared valley that has rusted or cracked |
| Gutter or downpipe repair | RM300 – RM1,500 | Clearing, resealing joints, re-falling or replacing a section |
| Replace cracked or broken tiles | RM600 – RM2,500 | Tiles disturbed along the party-wall line |
WhatsApp us your job details for a quote — we reply within the hour.
💬 WhatsApp for a quoteFor a higher-roof junction, the lasting repair is a base flashing turned up the wall with a counter flashing let into the wall above it, not another layer of sealant. For a shared gutter, check that it is sized for the water from both roofs before simply clearing it.
One contractor working on both halves in one visit is usually cheaper and more reliable than two contractors each patching their own side. The joint work is continuous, the flashing laps from one house to the next, and nobody can later blame the other side's workmanship.
Sometimes a neighbour is away, the house is tenanted, or the owner simply refuses. The party wall guide's steps apply: record the damage, write to the neighbour formally setting out the problem and what you want done, and keep copies. For a landed terrace the route for an unresolved claim is a civil claim; in a strata scheme the building's management and the Commissioner of Buildings are involved first.
Meanwhile you can protect your own side. A repair limited to your half, such as re-flashing your side of the junction or fitting a separate gutter, will not always stop a leak that starts on the other half, but it can reduce the water reaching your ceiling while the dispute is settled.
A shared roof needs shared maintenance. Before each rainy season, clear the shared valley or gutter, look along the party-wall top for cracked mortar and lifted flashing, and check any neighbour's downpipe that empties near your roof. ClickBina's monsoon roof checklist explains why blocked gutters cause more monsoon roof leaks than broken tiles do. If you or your neighbour plan an extension, agree how the new roof will meet the other house before the roofer starts.
WhatsApp us your job details for a quote: where the stain is, whether it follows the shared wall or the gutter line, when it drips, and whether the neighbour has done recent works. ClickBina is an experienced KL & Selangor contractor for whole-house refurbishment and trade coordination. Leak detection is RM300 – RM800 per visit, separate from any repair. We reply within the hour, and the price we agree is a flat price with no hidden charges. 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.
WhatsApp us your job details for a quote — we reply within the hour.
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