Does the Code set different rules for coloured concrete in Ontario?

We found no separate rules for coloured concrete in the 2024 Ontario Building Code.

For exterior flatwork, the Code requires a minimum compressive strength of 32 MPa at 28 days and a maximum water-to-cementing-materials ratio of 0.45. Those numbers do not change because colour is added. The Code's appendix note to section 9.3.1.7 does say that adding water to concrete on site can reduce strength and increase porosity and the propensity to shrinkage cracking, and that note applies to any exterior concrete pour, coloured or not.

Skilled Trades Ontario lists the Cement (Concrete) Finisher trade's scope as including pigmented, stained and dyed concrete, so the trade recognises colour work as part of the finisher's craft. The certificate is non-compulsory, meaning no one is required to hold it, and individuals practising the trade do not appear on the Skilled Trades Ontario public register.

What does vary with coloured concrete is the contractor's written specification, not the Code. The mix design, the timing of finishing passes, the sealing product and the maintenance instructions are all things to ask for in writing before work begins. A quote for coloured exterior concrete should spell out the specified compressive strength, the base preparation, the finishing method and whether sealing is included. The City of Ottawa's Hardscaping Contractor Licence is required for a business installing concrete patios, walkways, steps and similar hard landscaping features on private property; ask to see the licence and check the City's published list yourself.

Ask each contractor whether they have poured coloured flatwork before, and to show you the colour on a sample.