How to stop water seeping through a wall in Hong Kong

Water is seeping through one of the cement clad walls of my village house and staining the Internal wall. How do I remedy this?

First, check for any obvious places where water might be getting in. Any large cracks or broken areas. If the cement is damaged where the seeping occurs, use fast-drying cement (HK$20 for a small bag), which dries quickly even in wet conditions. Pay particular attention to areas around window frames.

If there are no obvious areas of damage, water could be penetrating through the surface of the cement itself, especially if it was applied a long time ago.

The best way to get around this is to apply a waterproof sealant such as those produced by French brand Dip (HK$300 for five litres).

If the facade also needs painting, you could kill two birds with one stone by using one of the new latex paints which have waterproofing qualities such as Kangaroo K606 water-based polyurethane waterproofing membrane, available in red, green, white or grey (HK$250 for four litres). All products mentioned are available from Yuen Fat Ho in Central, tel: 2546 8020.

What Causes Water Seepage in Hong Kong Apartments?

Having worked on hundreds of seepage problems across Hong Kong since 1996, I can tell you that the causes fall into a few common categories. Understanding which one you are dealing with is crucial because the fix is different for each:

• Typhoon-driven rain penetration: During typhoon season (June to October), wind-driven rain hits external walls at angles that normal rain never reaches. Hairline cracks that cause no problems for most of the year suddenly become entry points. Buildings on exposed hillsides in areas like Mid-Levels, The Peak, and Discovery Bay are particularly vulnerable.
• Ageing waterproof membranes: Many Hong Kong buildings built in the 1970s-1990s used waterproof membranes on external walls and flat roofs that have a lifespan of 15-25 years. Once these degrade, water finds its way through the concrete substrate. This is extremely common in village houses and low-rise buildings.
• Concealed pipe leaks: Older Hong Kong buildings often have water pipes embedded in walls. Over time, galvanised steel pipes corrode from the inside out, and copper pipes can develop pinhole leaks. The water seeps through the wall long before you notice dripping. If the wet patch on your wall is warm to the touch, it is likely a hot water pipe leak.
• Failed window and AC unit seals: Window frames and air-conditioning unit sleeves are notorious weak points in Hong Kong apartment walls. The sealant around these openings deteriorates with UV exposure and thermal expansion over the years.
• Upstairs neighbour's bathroom: In high-rise apartments, water seepage on a ceiling or upper wall often originates from the flat above. Failed waterproofing under their shower tray or bath is a very common culprit. This can be tricky to resolve as it requires cooperation from your neighbour.

How Much Does Waterproofing Cost in Hong Kong?

Costs vary enormously depending on the source and severity of the problem. Here is a rough guide to give you an idea:

• DIY crack repair with fast-drying cement: HK$20-50 for materials. Suitable for small, visible cracks on external cement-clad walls.
• Waterproof sealant (e.g., Dip brand): HK$300 for 5 litres. Enough to coat approximately 10-15 square metres of external wall surface.
• Waterproofing latex paint (Kangaroo K606): HK$250 for 4 litres. Good for combined waterproofing and repainting jobs.
• Professional external wall waterproofing: HK$3,000-8,000 for a single wall of a village house. For high-rise buildings, this becomes a building management responsibility and costs are shared among owners.
• Concealed pipe repair: HK$2,000-6,000 depending on access difficulty. This typically involves hacking out tiles to reach the pipe, making the repair, then retiling. See our guide on repairing damaged walls for what comes after.
• Full bathroom waterproofing membrane: HK$5,000-15,000 professionally installed, including floor and wall up to shower height.

For village houses and ground-floor units, I always recommend addressing external waterproofing before the wet season begins. The best time to do this work is during the dry months of November to March when surfaces are dry enough for sealants to bond properly.

When Should You Call a Professional?

Small cracks on an external cement wall are a manageable DIY fix. However, water seepage often has hidden causes that require proper investigation. Call a professional if:

• The seepage is persistent or worsening: If water continues to come through after you have patched visible cracks, the source is likely deeper than the surface. There may be failed waterproofing membranes, corroded pipes, or structural issues that need proper diagnosis.
• You are in a multi-storey building: Seepage problems in high-rise apartments often involve common areas, neighbouring flats, or building infrastructure. You may need to contact your building management office. Under the Building Management Ordinance, the incorporated owners are responsible for maintaining common parts of the building.
• Mould is appearing alongside the seepage: Where there is persistent damp, mould is never far behind. If you can see or smell mould, the problem has been going on longer than you think and needs thorough treatment beyond simple patching.
• The seepage is near electrical fittings: Water and electricity are a dangerous combination. If seepage is occurring near light switches, sockets, or wiring conduits, switch off the relevant circuit at the breaker box and get professional help immediately.

For more bathroom-related advice, browse our full range of articles in the bathrooms section.

Last updated: March 2026