Catalan to English Tech/Engineering Architecture

I'm not looking for a translation of the term "Canon" per se, here as advice as to which sense of the word is being used here.

"Canon" can mean a tax (e.g. the famous unpopular cannon on blank CDs) or it can have the sense of canonical, that which is established or that which is done.

In this sentence, I'm not sure which meaning is being used in the section between the asterisks:

"L’Eixample central tampoc no va restar al marge de les estratègies d’establiment residencial basades en l’habitatge unifamiliar, per bé que a la Barcelona de finals de segle XIX ***ja s’havia generalitzat el cànon de l’habitatge de renda que informava de la construcció de cases de veïns entre mitgeres**"

Does this mean that terraced housing was being influenced by a tax imposed on rented accommodation? Or does it mean that rented accommodation was becoming the norm and this was the impetus behind the building of terraced housing? (I lean towards the latter)..... Or have I been steered off track completely here?

Thanks in advance for your input.