Concrete step

The precast step on this 35 year old house finally gave way. I am going to pour its replacement. There are two cantilevered supports from the house foundation on which the old step sat. Can I just build my forms outside these and have them encased in the new concrete? Does there need to be a slight buffer between the step and the foundation, or can the concrete go right up against it?
This is Alberta - cold winters...

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