Decorative Finishes: Stains, Dyes & Exposed Aggregate

Decorative concrete is where a floor becomes a feature. But it’s also where “I expected it to look like the brochure” complaints come from, because concrete doesn’t behave like paint. This lesson covers the main decorative routes and how to get consistent, honest results.

Acid stains (reactive)

Acid stains don’t add colour — they react with the calcium in the concrete to produce a colour. The result is variegated, organic and unique to that slab.

• Pros: Penetrates the concrete (doesn’t wear off), beautiful natural variation, very durable.
• Cons: Unpredictable — the colour depends on the slab’s chemistry, so it’s not reproducible exactly. Can’t hit a specific brand colour.
• Best for: Commercial and public spaces where a natural, non-repeating look is wanted.

The honest pitch: Always tell the client acid stain is reactive and will look different on their slab than on a sample. Do a test patch and get sign-off before committing the whole floor.

Water-based stains & dyes

• Water-based stains behave more like acid stains but are easier to control and offer a wider, more consistent range.
• Dyes sit on the surface — more consistent colour, easier to match, but less durable and can wear in traffic. Usually sealed on top.

Exposed aggregate

Here the finish is revealed, not applied. You grind or shot-blast the top layer of cement paste away to expose the aggregate beneath.

• The aggregate in the slab is the design — so the slab’s aggregate needs to look good. If the slab has poor, dark or mixed aggregate, exposed aggregate will look bad.
• It’s a profile decision: how deep you cut determines the texture.
• Always sealed to protect the exposed aggregate and control staining.

Flaked (chip) finishes

Epoxy flake is a coating system where coloured vinyl flakes are broadcast into a wet epoxy base. High durability, high slip resistance, and a very commercial look (warehouses, gyms, retail). It’s a coating system — so all the moisture and profile rules from the epoxy course apply.

Getting consistency

The single biggest rule: test patch first. Whatever the method, do a representative patch, let it fully cure, and get the client’s written sign-off. Concrete variation is a feature, but the client needs to agree on the variation before you commit the whole floor.

Checklist: Choose the method for the look and traffic → inspect the slab’s suitability (especially aggregate for exposed finishes) → test patch → written client sign-off → full application → protect/seal.

Key takeaways

• Concrete is a canvas — but it's a reactive, non-uniform one. Plan for variation.
• Acid stains colour from within (reactive); dyes sit on the surface (consistent but less durable).
• Exposed aggregate is a finish you reveal, not apply — the slab's aggregate is the design.