Ask three contractors to price the same roof and the numbers can differ by a multiple. That is not (usually) dishonesty — it is because waterproofing cost lives in places a per-m² rate cannot see. Here is where the money actually goes, so you can budget realistically and read quotes fairly.
What waterproofing costs in Singapore, September 2026
The ranges below are taken from Singapore renovation and home-services platforms’ published guides, checked on 28 September 2026 and listed under verification sources at the end of this page. The one exception is PU injection, which no platform prices: that line is one waterproofing contractor’s published 2026 price guide, checked on 29 September 2026. Where no published range exists, the table says so instead of guessing. They are market indications, not Rayson quotations: the guides differ in what they include, GST, preparation and access among them, and no quotation is honest until the surface has been seen. They are here because a budget needs a starting number.
Toilets and bathrooms, HDB or condominium, per bathroom
| Job | Published range, S$ | What it usually covers |
|---|---|---|
| Waterproofing membrane line within a renovation | 400 – 1,500 | Budget to premium tier (OneCompare, July 2026); around 10 to 15% of a bathroom renovation |
| Hacking and disposal | 400 – 1,500 | Tiles, tile bed and the old membrane out (OneCompare) |
| Wall and floor tiling | 1,500 – 6,500 | Budget to premium tile and labour (OneCompare) |
| Basic works of one bathroom: hack, waterproof, tile | 3,000 – 5,900 | Before fittings (Qanvast, April 2024) |
| Full overhaul of one HDB bathroom | 4,500 – 9,000 | Typical figure including fittings (OneCompare) |
| No-hacking repair from above | Quoted after a flood test | Only where the membrane beneath is sound |
| PU injection grouting | 300 – 1,200 per job | Slab cracks and joint seepage; seals a crack, does not rebuild a membrane (one waterproofing contractor’s price guide, June 2026) |
| Making good a spalled ceiling below a leak | 300 – 1,200 | A patch the size of a phone to the whole toilet ceiling (Home & Decor, November 2024) |
Bathroom by bathroom, overlay against hacking, per square foot and the minimum charge, from a contractor’s 2026 guide checked on 2 November 2026: see the toilet waterproofing cost page.
Roofs
| System or job | Published range, S$ | Basis |
|---|---|---|
| Roof waterproofing, basic coating to premium membrane | 8 – 50 per m² | Home-services platform guide, updated August 2026 |
| Labour, standard residential roof | 1,000 – 3,000 per roof | Same guide, on top of the material rate |
| Localised patch repair | 200 – 800 | Same guide |
| Detail work at upstands, parapets, outlets and penetrations | Quoted on inspection | The line that separates two quotes for the same roof |
| Full re-membrane of a landed RC flat roof | Quoted on inspection | Removal, preparation and detailing set it, not the area |
| Metal roof coating and re-sealing | Quoted on inspection | Seams, fixings and corrosion decide it |
Balconies, car porches and planters
| Surface | Published range, S$ | Basis |
|---|---|---|
| Balcony or car porch roof | Priced as a small roof | The per-m² rate plus labour and detailing; quoted on inspection |
| Planter | Priced as a small tank | Empty, line, protect; quoted on inspection |
Read the numbers the right way: a S$450 toilet quotation and a S$3,500 one are not the same job. One is a membrane over the existing floor; the other hacks, re-membranes, flood-tests and re-tiles. The contractor guide sets out what the quotation must say for the two to be compared.
If the stain is on your ceiling and the toilet is upstairs, the repair happens in the flat above. The ceiling leak repair page covers who does it, who pays and what it costs.
Detailing beats area
The open field of a roof or deck is the easy part: prepare, prime, apply. The cost — and the risk — concentrates at the details:
- upstands and parapet terminations, where membranes must turn and anchor;
- drainage outlets, the single most common leak point;
- pipe and service penetrations, each one a hand-detailed interruption;
- joints and cracks, which move and must be treated as movement details;
- edges, gutters and thresholds, where systems end and water probes.
A plant roof crowded with services can carry several times the cost of a clean open deck of the same area — legitimately. When a quote is suspiciously cheap, the detailing scope is usually what went missing, and the details are exactly where leaks start. Industrial roofs are priced the same way, with the laps, fasteners and box gutters counted alongside the area; the industrial roof waterproofing page lists what a 1,000 m² roof takes in material.
System class sets the base price
- Cementitious and acrylic coatings are the economical end — cementitious for selected wet areas and protected surfaces, acrylic for exposed roofs and walls that shed water — with shorter recoat cycles. Rayson’s acrylic is SealForce AC10. Waterproof cement, a latex additive in ordinary cement, is not one of these systems; the waterproof cement guide sets out the difference.
- Liquid-applied membranes are the exposed-roof workhorse: seamless, cold-applied films that follow every detail. Rayson’s route here is SealForce RC40, a two-component, cold-applied aliphatic polyurea membrane — roller-, brush- or spray-applied, UV-stable, walkable and elastic through Singapore’s daily thermal cycling.
- Hot-spray pure polyurea such as SealForce SP200 is the premium route — fast-curing hot-spray application by specialist crews that returns the area to service quickly, which is often what pays for it on live sites, car park decks and containment work.
Higher class buys thickness, speed, elasticity and service life — the honest question is which duty the surface actually faces. Exposed tropical roofs, trafficked decks and bunds are different problems; the hub page for waterproofing in Singapore separates them.
The existing surface is half the quote
Waterproofing is rarely applied to a new, clean slab. Removing a failed membrane, drying and repairing the substrate, re-establishing falls so water reaches the outlets — this reinstatement work can equal or exceed the new system’s cost, and no serious contractor can price it without seeing the roof. A quote produced without an inspection is a guess with a signature.
Repair, recoat or replace
- Repair when the breach is local and the surrounding membrane is sound.
- Recoat when the membrane is ageing uniformly but still bonded — a liquid-applied overlay buys years at a fraction of replacement cost.
- Replace when adhesion has failed or water is tracking beneath the membrane — patching a floating membrane pays for the same leak twice.
Water travels: the stain on the ceiling is often metres from the breach. Spend on finding the real entry point before spending on coverage.
What Rayson’s material adds up to
The one line a manufacturer can write that a contractor cannot is the material itself, from the published data sheets:
- Toilets and bathrooms. SealForce WB20 is applied in two coats at 0.4 mm wet film, about 0.56 kg/m² per coat. A typical HDB toilet, a 3 m² floor with 300 mm turn-ups and a shower wall to 1.8 m, takes about 8 to 12 kg for two coats: under one 20 kg pail, which covers about 18 m² at two coats.
- Exposed roofs. SealForce RC40 is applied at 1 to 1.2 kg/m² over two layers, so a 21 kg set covers about 17 to 21 m² of cementitious roof, plus primer.
- Pitched and tiled roofs, external walls. SealForce AC10 is applied at about 0.68 kg/m² per coat, so a 20 kg pail covers about 14 m² at two coats as a roof coating, or about 9 m² at three coats with reinforcing fleece. Its primer, SealForce AP05, goes on first at about 0.1 to 0.3 kg/m²: a 20 kg pail primes about 65 to 200 m².
- Decks and heavier-duty wet areas. SealForce RC30 is applied at 1.5 to 1.8 kg/m² in two coats, so a 26.5 kg set covers about 15 to 17 m². The toilet waterproofing page shows the job step by step in a Hougang HDB toilet, from hacking to the flood test.
- Walls, cracks and windows. Seepage through a crack or around a window frame is a repair, not a re-membrane, and is quoted on inspection: see wall crack and seepage repair and window leak repair.
Divide the current pail price, available from Rayson on request, by the coverage and you have the material line to check any quotation against. On a S$3,000 to S$9,000 toilet job the membrane material is a small fraction; what you are paying for is hacking, detailing, the flood test and the tiling, which is why the detailing scope, not the pail, is where quotes should be compared.
Warranty: who gives what
Two warranties sit behind a waterproofing job, and a quotation should name both. Rayson warrants its SealForce membranes against manufacturing defects from the date of supply: three years for SealForce WB20, the membrane beneath tiles in toilets, bathrooms and balconies, and five years for the SealForce roof and deck membranes. Both are conditional on the material being stored and applied in accordance with the technical data sheet and the membrane being flood-tested before it is covered; the remedy is replacement material. The workmanship warranty is separate: its period, what it covers and what it excludes belong on the quotation, which is Rayson’s when Rayson quotes the job. Ask for both in writing before you order, and treat a quotation that names neither as incomplete.
Comparing quotes: the five lines that matter
- System and applied thickness (with the TDS named).
- Preparation and repairs — included or excluded.
- Detailing scope: upstands, outlets, penetrations, terminations, joints.
- Warranty — years, and what it actually covers.
- Programme and weather allowance.
Two quotes stating all five are comparable. Headline rates are not. The contractor guide expands these five into the twelve lines a full quotation should show.
Getting a real number
Send photos of the surface and its details, the approximate area, the history (when it last leaked, what was done), and the access situation — Rayson will recommend a system class honestly, including when a repair rather than a re-waterproof is the right answer: request a quote or WhatsApp the photos.