Liquid Coatings – Coating Material Coverage and Costs
How to Calculate Liquid Waterproof Coating Coverage and Cost per m²
Understanding how much liquid waterproof coating you need — and what it will cost per square metre — depends on key material properties like solids content and specific gravity.
These determine how thick your coating will be once cured and how much product is required to achieve the desired Dry Film Thickness (DFT).
1️⃣ Understanding Solids Content
When a liquid coating is applied, the resin, pigments, additives, and solvents evaporate during curing — leaving only the solid components behind as a continuous protective film.
The solids content is expressed as a percentage of the total volume in the container.
100% Solids – The Most Efficient Coatings
If a coating is 100% solids, the amount you apply wet will match your final dry thickness.
For example:
Apply 2mm wet → Achieve 2mm dry (DFT)
This means less material waste, more predictable coverage, and reduced labour time.
Example: Coatings with Less Than 100% Solids
If your coating is 50% solids, half the material evaporates.
That means:
Apply 2mm wet → Only 1mm dry
To achieve 2mm DFT, you’d need to apply 4mm wet.
💡 The takeaway: 100% solids coatings give you double the effective coverage and performance consistency.
2️⃣ Specific Gravity and Its Effect on Coverage
The specific gravity (density) of a coating determines how much it weighs per litre — and therefore how much area it can cover.
Example: Based on Water (Specific Gravity = 1)
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10 litres of water covers 10 m² at 1mm thickness (10 kg total weight).
Typical Coating Example (Specific Gravity = 1.3)
Most liquid coatings are denser than water.
If a product has a specific gravity of 1.3:
1.3 kg covers 1m² at 1mm thickness
13 kg covers 10m² at 1mm thickness
To achieve a 2mm dry film, you’d need 26 kg of material for every 10m².
3️⃣ Packaging and Coverage by Weight
Most manufacturers package coatings in 10 kg, 20 kg, or 25 kg tins.
| Coverage | Thickness | Material Required | Notes |
|---|---|---|---|
| 10m² | 1mm | 13 kg | Based on 1.3 specific gravity |
| 10m² | 2mm | 26 kg | Standard thickness for durability |
| 10m² | 2mm (50% solids) | 52 kg | Requires double due to evaporation |
⚠️ If the material is not 100% solids or contains plasticisers, expect higher material usage.
4️⃣ The Hidden Cost of Low-Solid or Plasticised Coatings
Many two-part roof coating systems contain plasticisers to improve flexibility and elongation.
However, prolonged UV exposure causes these plasticisers to migrate and evaporate, making the coating brittle and prone to cracking over time.
Long-Term Problems of Non-Aliphatic Coatings
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UV degradation
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Loss of elasticity
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Splitting or blistering
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Water ingress and premature failure
Choosing 100% aliphatic or UV-stable coatings ensures durability, colour stability, and a long-lasting waterproof barrier.
5️⃣ Additional Material & Application Costs
Most liquid coatings (except SilaCote) require:
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A primer to prepare the surface and ensure adhesion
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A top coat for UV and weather protection
These extra layers add cost and application time — so always factor them into your cost-per-m² calculation.
💡 Key Takeaways
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100% solids coatings deliver full coverage and predictable thickness.
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Specific gravity determines true material usage and cost.
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Plasticized coatings may crack or fail under UV exposure.
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SilaCote and other aliphatic coatings provide UV-stable, long-term protection.
Need Help Calculating Your Project Coverage?
Our technical team can help you determine exactly how much material you need for your project and recommend the most cost-effective, UV-stable solution.
📞 Call 01268 472358 | ✉️ info@clevershield.co.uk