Updated 2026-10-10 · by Seepwise
Short answer: Check that the contractor finds the source before quoting, gives an itemised quote that names the membrane system and coats, includes a ponding or water test, handles the HDB permit if hacking is involved, and puts warranty terms in writing. For larger jobs, BCA's Contractors Registration System lists firms under workhead CR13, Waterproofing Installation.
Seepwise writes these guides from HDB, MND and BCA sources and published Singapore price data; each claim links to where it comes from.
Eight checks before you sign
- They find the source first. A moisture map, a dye or ponding test, a look at the unit above or the roof. A quote without a finding is a guess.
- The quote is itemised. Preparation, the membrane system by name, number of coats, screed, tiles, disposal, GST.
- A water test is included. A ponding test of at least 24 hours before tiling on wet areas (guide); a water test of outlets on roofs.
- Permits are handled. In HDB flats, hacking bathroom floors generally needs a permit applied for by the renovation contractor (Hometrust).
- Warranty terms are written. What is covered, for how long, and what voids it.
- Photos of each layer. The membrane is buried under screed and tiles; photos are your only evidence of what went in.
- Registration for larger jobs. BCA’s Contractors Registration System has a waterproofing installation workhead, CR13, with firms listed by grade (BCA directory).
- They tell you when not to do the job. A new BTO under warranty, a roof that is the Town Council’s, a leak that is really the aircon drain.
Red flags
| Red flag | Why it matters |
|---|---|
| “We can fix it from your ceiling” | The source is usually in the slab above |
| Price given before anyone looks | The substrate drives the price |
| No ponding or water test | Nothing proves the membrane holds |
| Paint-on sealer called “waterproofing” | Not a membrane system |
| No written warranty terms | Nothing to hold them to |
Bottom line
A good contractor diagnoses before quoting, names the system, tests the result and writes down the warranty. Request an inspection and we match you with a specialist who works this way.
Want this checked at your home?
A specialist calls you back to book an inspection.
Request received.
A specialist will contact you on the number you gave. If water is near electrics, switch off that circuit at the distribution board and keep clear until then.
More questions
What is BCA workhead CR13?
The Contractors Registration System workhead for waterproofing installation. BCA's directory lists registered firms by grade.
Should I accept a quote given over the phone?
For roofs and leaks, no. The substrate and the source decide the price; a firm price without an inspection is a guess.
How many quotes should I get?
Three is common advice, compared line by line on the same scope.