Why Your Waterproof Coating Peeled Off — 7 Real Causes (Ghana 2026)
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When a waterproof coating peels, the coating is rarely what failed. The bond failed. In almost every case we are called to inspect in Ghana, the material was capable and something about the surface, the timing or the number of coats meant it never had a chance to hold. Here are the seven real causes, how to identify yours, and exactly what to order to put it right.
Start by Reading the Flake
Before diagnosing anything, pick up a piece that has lifted and turn it over. The back of it tells you most of the story.
| What is on the back | What it means |
|---|---|
| Dust, chalk, or loose cement | Preparation failure — it bonded to dirt, not concrete |
| Old paint or a previous coating | Applied over a failed layer — the old one let go |
| Sound concrete stuck to it | Adhesion was good; the substrate itself was weak |
| Clean back, flake still flexible | Moisture pushed it off from behind |
| Brittle, cracks when bent | Film too thin, or wrong material for the movement |
| White crystals on the back | Salts — rising damp or a damp substrate |
1. It Was Applied to a Damp Substrate
The most common cause, and the most preventable. Polyurethane will not bond to a wet surface. It needs dry concrete — dry through the surface layer, not dry to a quick touch after an hour of sun.
How it presents: lifts in sheets with a clean back, often bubbling first, usually across a whole area rather than in patches.
2. The Surface Was Never Properly Prepared
Dust, laitance, oil, algae and flaking old paint all prevent adhesion. A membrane rolled onto a dusty roof bonds to the dust, and dust does not bond to anything.
How it presents: peels easily by hand, powder on the back, typically across the whole roof.
This step is invisible once the coating is on, which is exactly why it gets skipped. If you are on site for one hour of your project, be there for the preparation — not the coating.
3. It Was Coated Over a Previous Failed Layer
New coating over old, failing coating inherits the old bond. The new material may be perfectly sound and still come away, because what it is attached to was already letting go.
How it presents: the back of the flake carries the old coating, sometimes in two visible layers.
4. Only One Coat Was Applied
A single coat cures unevenly, retains pinholes where the roller lifted, and leaves thin spots over aggregate. It looks finished on the day and behaves like decoration in the rain.
How it presents: brittle, thin flakes; failure concentrated at high spots and around aggregate; pinholing visible when wet.
Two coats, the second perpendicular to the first, at roughly 1 kg per square metre in total. If a whole roof was done with a fraction of that, the film was never thick enough regardless of who applied it.
5. It Was Applied to the Negative Side
This one is chemistry, not workmanship. On the positive side — a roof, or the outside of a foundation wall before backfill — water pushes the membrane into the concrete. On the negative side — the inside face of a basement wall, or a sump pit — pressure pushes against the back of the film and lifts it off.
How it presents: blistering and peeling on an internal below-grade wall, often with damp or salts behind it, usually within a season.
No polyurethane survives this, at any thickness or price. That job needs a cementitious crystalline system — see positive vs negative side.
6. There Was Rising Damp Underneath It
If a wall is wet at the base with a horizontal tide line and white powdery deposits, water is travelling up through the wall from the ground. Coating the face traps it, and the salts crystallise behind the film and push it off.
How it presents: failure confined to the lower part of a wall with a fairly level upper boundary, salts on the back of the flake.
The coating never had a chance. This needs a chemical damp-proof course — see our rising damp guide.
7. Rain Arrived Inside the Cure Window
Polyurethane needs a dry window to cure. Rain on an uncured film disrupts the surface, causes patchy adhesion, and can leave a permanently weakened layer.
How it presents: patchy failure with no obvious pattern, sometimes a dull or mottled surface where the rain caught it.
The Cause That Is Not on This List
Notice what is missing: "the product was bad". It happens, but it is rare — and be sceptical of it as a diagnosis, particularly from whoever applied it. Genuine material failure shows as uniform degradation across the whole area regardless of substrate, with no pattern relating to low spots, wall bases, or where the crew stopped for the day. Almost every failure that does show a pattern is telling you about application, not chemistry.
What to Order to Fix It
Work out your quantity in one line
Measure the area, then multiply by 1 kg per m². That is our measured consumption across two coats — taken from completed jobs, not a label figure. A 10kg bucket covers about 10 m² finished, a 5kg about 5 m².
| Roof size | Coating needed | Order | Cost |
|---|---|---|---|
| 20 m² | 20 kg | 2 × 10kg | GHS 2,000 |
| 50 m² | 50 kg | 5 × 10kg | GHS 5,000 |
| 100 m² | 100 kg | 10 × 10kg | GHS 10,000 |
Add 15–20% if you measured from a plan and the roof has a parapet, and 10–15% more if the slab is bare or freshly stripped. Ordering 20+ units? Use code FESTCONTRACTOR15 for 15% off.
The three things a proper repair needs:
| Product | Price | When you need it |
|---|---|---|
| Plugging King | GHS 100 | Only if water is actively flowing. Stops it in seconds so the surface can dry. |
| Leak Seal Tape | GHS 250 | Every job. Bridges upstands, penetrations and wall-to-slab junctions before coating. |
| Polyurethane Coating 10kg | GHS 1,000 | The membrane itself. 20-year design life, two coats, 1 kg/m². |
→ Order Polyurethane Coating 10kg — GHS 1,000 | 5kg — GHS 500
Same-day dispatch in Greater Accra. Nationwide delivery. 3-year manufacturer warranty.
The Repair Sequence
- Establish the cause first. Recoating without diagnosing buys the same failure again.
- Remove all failed material back to sound substrate. Anything loose comes off.
- Fix the underlying condition — dry the slab, install the DPC, or change system if the water is on the negative side.
- Prepare properly — clean, dust-free, dry.
- Tape the junctions — upstands, penetrations, wall-to-slab angles.
- Two coats, perpendicular, at about 1 kg/m² total, inside a dry window.
Before You Order Anything — One Free Check
This costs us a sale, so take it as honest: clear your gutters first. A meaningful share of what gets reported to us as coating failure turns out to be a blocked gutter backing water up over the lip and down inside the wall. The ceiling stain looks identical and the coating on the roof is fine. Clear them, wait for the next serious rain, and see what is still wet.
Not Sure? Send Us a Photo
Photograph the failed area, and photograph the back of a lifted flake. Those two images usually tell us the cause without a site visit — and we will work out your exact quantity before you order. WhatsApp 0555 548 001.
Or book a free site assessment. Installed work carries a 3-year workmanship warranty and a 3-year manufacturer material warranty, with a 20-year design life on the membrane.