# Balcony leaking to the unit below in Singapore: what to check first, what it costs, who to call Source: https://honestfix.cf-migrate-pulse-web.workers.dev/guides/balcony-leaking-to-the-unit-below · checked 15 Sep 2026 the Honestfix team · checked 15 Sep 2026 A balcony or terrace leaking to the unit below means water is soaking through your balcony's floor slab and dripping into the ceiling of the flat directly underneath, rather than draining away on the surface. Sika, a [waterproofing](/waterproofing) systems manufacturer, notes that water infiltration into a structure "can cause expensive and irreversible damage" once it gets past the surface finish. ## What to check first Stand on the balcony after rain, or run a bucket of water across it, and watch where it goes. Water that pools instead of running to the drain, or takes an obviously long time to clear, is your first clue. Check the drain outlet itself for leaves, sand or renovation debris — this is the one check that costs nothing and rules out the simplest cause before you call anyone. Look at the finish for hairline cracks in the tile grout, screed or sealant where the balcony meets the wall, especially near planters or where furniture legs have sat for years. Photograph anything you find with a date, for whoever quotes the job. Tell your downstairs neighbour before you start any check that involves water on the floor — a bucket test on your side shows up as a fresh drip on theirs within minutes, and an unannounced one reads as a new leak, not a diagnosis. ## The likely causes, in order **A failed waterproofing membrane (most common).** The most common cause is a failed waterproofing membrane under the balcony's tiles or screed, which lets water that should evaporate or drain instead travel down through the slab. Waterproofing is its own licensed category of building work under BCA's Contractors Registration System, which groups building work into about 50 workheads under five main registration groups. A balcony membrane sees more direct rain and sun than an internal bathroom's, so it tends to fail earlier. **A blocked or poorly sloped drain.** The second cause is a blocked or poorly sloped floor drain, so water pools on the balcony instead of running off, and standing water finds any weak point in the finish far faster than moving water does. Clearing the drain is a first check that costs nothing before assuming the membrane has failed, and it is worth doing before calling in a contractor from HDB's Directory of Renovation Contractors. **A crack in the parapet or a failed sealant joint.** The third cause is a crack in the parapet wall or a failed sealant joint where the balcony meets the main wall, which lets driving rain in sideways rather than through the floor. This points to the building envelope rather than the floor membrane, and changes what a contractor needs to open up. It is often a smaller, cheaper fix than re-waterp[roofing](/roofing) the whole floor. **Renovation damage below the surface.** If the leak started soon after any renovation work on the balcony — new tiles, a new planter box, drilled fixings — the membrane may have been punctured during that work rather than having failed on its own. Mention any recent renovation to whoever inspects it. ## When to call, and who Call a waterproofing contractor once you have ruled out a simple blocked drain and confirmed the leak is coming from your balcony and not somewhere else in the building envelope. Bring your photos and the date the leak was first noticed. If you are in an HDB flat and the drip is affecting the unit below, your Town Council can help coordinate a joint inspection so both floors are checked in the same visit. In a condo, loop in the MCST or managing agent, especially if the balcony sits above common property or a shared facade. Stop and call your Town Council, MCST or a BCA-registered contractor, not a general [handyman](/handyman), if the ceiling below is bulging, sagging or dropping plaster, or if the leak reaches a light fitting or power point. That is a structural or electrical safety question, not a routine waterproofing job. ## What it costs Ask two or three for a written quote against the same scope. Describe the balcony's size, whether it is fully open or covered, and whether the leak is confirmed as the membrane or still unconfirmed, so each quote is priced against the same job. A quote for "reseal balcony" with no inspection behind it is a guess. Ask whether hacking and removing the old finish, the membrane itself, the flood test, and re-tiling are priced as separate lines. Bundled quotes are hard to compare against a second one. ## Who to call, and how to judge them Waterproofing work in Singapore, including balcony and terrace jobs, is registered under BCA's Contractors Registration System, which groups building work into about 50 workheads under five main registration groups. Ask which workhead a contractor holds before booking. An ACRA registration confirms the business exists, nothing more. Pair it with the BCA workhead check and a written flood-test guarantee. Prefer a contractor who inspects the drain and the fall of the floor before quoting, not just the visible cracks. A balcony that drains badly will fail again even with a brand-new membrane. A waterproofing contractor checks your balcony floor and drain first, not the ceiling below: they test the fall to the drain, look for the membrane failure point, then hack, re-lay and flood-test before any new tile or screed goes down. ## Frequently asked questions **Why is my balcony leaking into the flat below?** A balcony or terrace leaking to the unit below means water is soaking through your balcony's floor slab and dripping into the ceiling of the flat directly underneath, rather than draining away on the surface. **What's the most likely reason a balcony leaks?** The most common cause is a failed waterproofing membrane under the balcony's tiles or screed, which lets water that should evaporate or drain instead travel down through the slab. **Could it just be a blocked drain and not the membrane?** Yes — the second most common cause is a blocked or poorly sloped floor drain, so water pools on the balcony instead of running off; clearing the drain is a first check that costs nothing before assuming the membrane has failed. ## Sources - [Sika Singapore, "Waterproofing"](https://sgp.sika.com/en/construction/waterproofing.html) (fetched 15 Sep 2026) - [BCA, "Contractors Registration System (CRS)"](https://www1.bca.gov.sg/growth-and-transformation/procurement/registration-of-built-environment-firms/contractors-registration-system-crs/) (fetched 15 Sep 2026) - [HDB, "Directory of Renovation Contractors (DRC)"](https://www.hdb.gov.sg/business-partners/renovation-contractors/directory-of-renovation-contractors-drc) (fetched 15 Sep 2026) [Compare waterproofing providers](/waterproofing) and give each the same three answers: what the drain test showed, whether the finish is cracked, and how long the leak has been going on. ## Related - [Water dripping from the ceiling: what to do before help arrives](/guides/ceiling-leak-at-night) — Guide: Water dripping from the ceiling in Singapore: keep clear of a sagging ceiling, stay away from wet electrics, find the source, and who to call tonight. - [Ceiling leak from the unit above in Singapore: what to check first, what it costs, who to call](/guides/ceiling-leak-from-the-unit-above) — Guide: A ceiling stain almost always traces back to a wet area directly above yours. - [Flat roof ponding water in Singapore: what to check first, what it costs, who to call](/guides/flat-roof-ponding-water) — Guide: Standing water on a flat roof is also a mosquito breeding risk, not just a leak risk. - [Waterproofing in Singapore — compare providers](/waterproofing) — Waterproofing - [Damp wall in Singapore: what to check first, what it costs, who to call](/guides/damp-wall) — Guide: A damp wall usually traces back to a pipe, a shared stack, or rain penetration — find which before booking waterproofing. - [Water seepage in the ceiling in Singapore: what to check first, what it costs, who to call](/guides/water-seepage-in-the-ceiling) — Guide: A stain that grows slowly is not the same fault as a drip at night.