8 Best Waterproofing Contractors in Singapore (August 2026)

Before you compare contractors, it helps to know what they are actually selling, because waterproofing is not one product. There are three broad systems, and a good specialist picks the right one for the surface rather than defaulting to whatever they have in the van.

Cementitious waterproofing is a cement-based slurry that bonds to concrete and screed. It is rigid, cheap and the workhorse under bathroom and kitchen tiles, but because it does not flex much it can crack if the structure moves. Liquid PU, or polyurethane, membrane is a seamless coating that stays flexible, so it handles the movement and thermal expansion of exposed surfaces like balconies and flat roofs far better. PU-cement hybrids try to give you both, the bond and rigidity of cement with the flexibility of PU, and they are the go-to for tricky wet areas and planter boxes that see standing water.

Where it goes matters as much as what it is. A bathroom or toilet needs waterproofing laid under the screed and tiles, which is exactly why a real fix often means the membrane, not the grout you can see. A balcony is exposed to sun and rain, so it wants a flexible membrane. An RC flat roof takes the harshest beating and usually gets a torch-on or liquid PU system. And a planter box is a quiet killer, because soil holds water permanently against the structure and needs a tanking-grade treatment.

The single most important habit to look for is leak detection first. Before anyone hacks a single tile, the contractor should trace where the water is actually coming from, using moisture meters, thermal imaging or ponding tests, because the visible damp patch is often nowhere near the real breach. A firm that reaches for the hacking tools before it has diagnosed the source is guessing with your money.

Prices swing with the size of the area, how bad the ingress is, which membrane system is specified, and whether the crew has to hack and reinstate tiles. Non-hacking treatments are cheaper and faster but are not right for every failure, while a full hack-and-retile costs more because you are rebuilding the wet area from the screed up. Always get the leak diagnosed and the scope written down before you accept a number, and treat these figures as a guide rather than a quote.

1. Detection before demolition. The contractor should trace the actual leak source with moisture meters, thermal imaging or ponding tests before hacking anything. Good waterproofing follows the standards and good-industry-practice guidance the Building and Construction Authority (BCA) sets for building envelopes and wet areas, and a serious firm can talk about that rather than just quoting a surface coat.
2. The right system for the surface. Cementitious under bathroom tiles, flexible PU membrane on balconies and exposed roofs, PU-cement hybrids for planters and heavy wet areas. A firm that recommends the same product for everything is selling convenience, not a fix.
3. A real warranty, in writing. Five to ten years on the workmanship, with a clear promise to return free if the leak recurs. The warranty length is the most honest signal of how confident a contractor is in the work.
4. BCA registration and safety certification. A BCA-registered waterproofing contractor and BizSafe certification tell you the firm meets recognised standards, which matters most on roof and rope-access jobs.
5. They understand the HDB inter-floor leak process. For a ceiling leak between HDB floors, the flat owners above and below share the cost of joint investigation and repair by default, and HDB offers a mediation route if the two households cannot agree. A contractor who has done these jobs knows how to document the source so the shared-cost conversation with your neighbour stays civil.

I am not a waterproofing company. I built this list the way I research any building-repair category: reading through Google reviews and local guides, checking each firm's live website for the methods it actually uses and how it diagnoses a leak, and weighing credentials like BCA registration and BizSafe certification against the marketing claims.

Ratings, prices and warranties shift over time, so treat the figures here as a starting point rather than a quote, and confirm the current details with the contractor before you commit. My aim was simple: give you a shortlist I would genuinely call myself, led by the firms that diagnose before they demolish.

Because the tiles and grout you can see are not the waterproof layer. In a properly built bathroom the actual membrane, whether cementitious or a liquid system, sits on the concrete slab and screed, underneath the tiles. Tiles and grout shed most water but they are porous over time, so water that gets through relies on the hidden membrane below to stop it reaching the structure and the ceiling of the unit beneath. That is why a genuine fix for a failed bathroom often means getting down to the membrane, and why simply regrouting the surface rarely stops a real leak for long.

By default the two households share it. Under HDB's inter-floor leak framework, the flat owner below and the flat owner above are each treated as responsible for helping resolve a ceiling leak, so the cost of the joint investigation and the resulting repair is typically split between them rather than pinned entirely on the upstairs unit. If the two sides cannot agree on the cause or the cost, HDB provides a mediation service to help them reach a settlement. You can read the current process on the HDB website, and it is worth engaging a contractor who can produce a clear written diagnosis, because that evidence is what keeps the shared-cost discussion factual.

A properly installed waterproofing system generally lasts anywhere from around five years for lighter surface treatments to fifteen or twenty years for a full membrane laid under tiles, depending on the system, the surface and the quality of the workmanship. Exposed areas like balconies and flat roofs age faster because of constant sun and rain, while a protected bathroom membrane can last much longer. This is exactly why the warranty length a contractor offers is such a useful signal, and why a diagnosis-led repair beats a quick surface patch that fails again in a year.

Often yes. Non-hacking methods like flood infusion and PU injection seal many toilet and bathroom leaks from the surface, without removing tiles, and can resolve the problem in about a day. They are cheaper, cleaner and ideal for an occupied home. The catch is that they are not right for every failure. If the underlying membrane has broken down badly or the screed is saturated, a proper fix means hacking, re-waterproofing and re-tiling. An honest contractor will tell you which situation you are in rather than promising a surface fix for a structural problem.

The good ones do, and it is the first thing I would ask about. Reputable specialists back their workmanship with a written warranty, commonly five years and up to ten years on certain systems, and the best will return to re-treat free of charge if the leak comes back within that period. Some firms go further with a refund guarantee if a recurring leak is not resolved. Get the warranty terms in writing, including what is covered and for how long, before you accept the quote.