How Many Coats of Polyurethane Do You Really Need? Ghana
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Two coats, every time — that is the honest answer. Polyurethane waterproofing coverage figures are always published per coat, and every roof needs two coats applied in different directions to close pinholes and thin spots. A 5kg pail covers 10-20 m² finished after both coats; a 10kg pail covers 20-40 m² finished. Anyone quoting coverage without saying \"per coat\" or \"finished\" is leaving out the number that determines whether you have enough material.
Why This Confuses So Many Buyers
Product coverage figures in Ghana's waterproofing market are almost always printed per coat, because that's how the manufacturer tested them. But waterproofing systems are designed and warrantied as two-coat systems — the first coat seals the substrate and fills the pores of the concrete or metal, the second coat, applied at 90 degrees to the first, closes any pinholes or thin patches the first coat missed. Quote the per-coat figure as if it were the finished figure, and a customer buys half the material the job actually needs.
The Numbers, Stated Two Ways
| Pail Size | Coverage Per Coat | Finished Coverage (2 Coats) | Price |
|---|---|---|---|
| 5kg | 20-40 m² | 10-20 m² | GHS 500 |
| 10kg | 40-80 m² | 20-40 m² | GHS 1,000 |
The Verified Working Rate
For take-off and budgeting purposes, use approximately 0.4 kg of coating per square metre of roof, across both coats. This isn't a rounded manufacturer estimate — it's drawn from a documented 370 m² roof and wall project at Kpone Katamanso, which used 150 kg of coating in total, working out to 0.41 kg per square metre. If a quote you've received implies a much lower kilogram-per-square-metre figure, ask directly how many coats it assumes.
Why a Second Coat Isn't Optional
A single coat of polyurethane, no matter how thickly applied, cannot be relied on to close every pinhole across an entire roof. Concrete substrates have pores, hairline cracks, and surface irregularities that absorb coating unevenly — the first coat naturally settles thinner in some spots than others. The second coat, rolled or sprayed at 90 degrees to the first, fills exactly the spots the first coat missed. Skipping it doesn't halve your protection; in practice it leaves specific weak points that fail first, usually at low spots where water sits longest.
How to Check a Quote Before You Buy
Ask two questions of any contractor: how many kilograms of material does the quoted price include, and is that for one coat or two? If the answer doesn't add up to roughly 0.4 kg per square metre for your roof area, the quote is either underspecifying material or hoping you won't do the maths. This applies whether you're buying material to self-apply or hiring installation — the kilograms don't change based on who's holding the roller.
Related Work
The 0.41 kg/m² verified rate comes from our Kpone Katamanso case study, a 370 m² roof and wall job using 150 kg of coating across two coats.
Frequently Asked Questions
How many coats of polyurethane waterproofing do I need?
Two, applied in different directions, on every job.
Why do some quotes only mention one coat?
To make the material cost look lower while under-delivering on protection.
How much polyurethane coating do I need for my roof?
Roughly 0.4 kg per square metre across both coats. A 5kg pail finishes 10-20 m²; a 10kg pail finishes 20-40 m².
Does a thicker single coat work as well as two thinner coats?
No — it cures unevenly and still leaves pinholes uncovered. Two coats at 90 degrees is the method that closes gaps.
Related Resources
- How to Apply Polyurethane Waterproof Coating
- Waterproofing Cost per Square Metre in Ghana
- Polyurethane: The Complete Guide
- Waterproofing Mistakes to Avoid
Not sure how much material your roof needs? Book a free site measurement or call 0555 548 001.