Polyurethane vs Cement Waterproofing: Which Is Better for Ghana?
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Polyurethane vs Cement Waterproofing: A Ghana Decision Guide
If you're waterproofing a roof, wall, or water tank in Ghana, you'll come across two main families of waterproofing materials: polyurethane (PU) liquid coatings and cement-based waterproofing. They both work, but they're suited to different jobs. Here's how to choose the right one for your project.
Quick Comparison
| Feature | Polyurethane | Cement-Based |
|---|---|---|
| Application | Liquid — brush, roller, spray | Mixed and applied like plaster |
| Flexibility | Stays flexible — bridges cracks | Rigid — can crack with movement |
| UV / heat resistance | Excellent, stable to +80°C | Poor without a topcoat |
| Which side of the water? | Positive side only | Works on the negative side |
| Design life | 20 years | Varies by system and exposure |
| Best for | Roofs, terraces, balconies, bathrooms, external foundation walls before backfill | Basements and below-grade walls, machine pits, sump pits, water-retaining structures |
| DIY-friendly | Yes | Requires more skill |
Polyurethane: The Strengths
Polyurethane is a flexible liquid coating that cures into a seamless rubber-like membrane. This matters in Ghana for three reasons:
- Roofs and walls expand and contract as the sun heats them and they cool at night. PU stretches with the building. Cement doesn't — which is why rigid cement waterproofing on an exposed roof often cracks after a few seasons.
- Ghana's UV is intense. PU is UV-stable. Cement degrades in direct sun unless covered with a topcoat.
- It's straightforward to apply. Brush, roller, or spray. Two coats, the second perpendicular to the first.
The Distinction That Actually Decides It: Positive vs Negative Side
This is the part most people get wrong, and it is the reason so many basement jobs fail in Ghana.
Positive side means the coating is applied on the face the water arrives at — the top of a roof, or the outside of a foundation wall before it is backfilled. Water pushes the membrane into the concrete. Polyurethane is excellent here.
Negative side means the coating is on the opposite face — the inside of a basement wall, or the inside of a sump pit. Water pressure pushes against the back of the film and lifts it off the concrete. Polyurethane will not survive this. It blisters and peels, usually within a season, and it takes the paint with it.
Negative-side work needs a cementitious crystalline system, which grows into the concrete's pore structure rather than sitting on top of it. If a contractor offers to fix a damp basement by painting PU on the inside face, they are selling you a repeat visit.
When Cement Waterproofing Wins
Cement-based waterproofing isn't inferior — it is the correct choice for specific conditions:
- Basements and below-grade walls that cannot be excavated — negative-side work, as above
- Machine pits, sump pits and effluent tanks — permanently in contact with standing water and under pressure from outside
- Water-retaining structures — the crystalline action seals against constant hydrostatic head
On swimming pools the answer is usually both: a cementitious crystalline base on the shell, then a two-coat polyurethane membrane, then tile adhesive and tiling. The crystalline handles the pressure; the PU handles the movement.
What About Your Roof?
For most Ghanaian homeowners dealing with a leaking concrete roof, polyurethane is the right answer. It seals the leak, survives the heat and rains, and you can apply it yourself with a roller. Our 5kg Polyurethane Coating and 10kg Polyurethane Coating are made for that job.
Size it on about 0.4 kg per square metre across two coats — so roughly one 10kg bucket per 25 m² of roof. Note that coverage figures on the label are quoted per coat, so halve them before you order.
Cost Over Time
Cement waterproofing is often cheaper upfront. On an exposed roof, though, a rigid system in Ghana's thermal cycle typically needs redoing far sooner than a flexible one, so across a twenty-year horizon polyurethane usually costs less. Below grade the comparison doesn't apply — there, cement is not the cheaper option, it is the only one that works.
The Bottom Line
- Roof, terrace, balcony, bathroom, external foundation wall before backfill: Polyurethane
- Basement interior, sump pit, machine pit, negative side generally: Cementitious crystalline — not PU
- Swimming pool: Crystalline base plus PU membrane, then tile
- Damp at the base of a wall with a tide line and salts: Neither — that is rising damp and needs a chemical DPC
- Quick emergency fix on a crack or joint: Neither — use our Waterproof Leakage Spray or Butyl Rubber Tape
Need Advice on Your Specific Project?
Send us a WhatsApp on 0555 548 001 with a photo of the area and we'll recommend the right product — including telling you when the answer isn't one of ours. Free consultation, no pushy sales. All installed work carries a 3-year workmanship warranty and a 3-year manufacturer material warranty.