TORONTO — An Alphabet company's vision for a "smart city" project in Toronto includes buildings made of timber that are five times the current limit, potentially steering the company into the challenges of timber innovation in Canada.

Sidewalk Labs' proposal includes developing 30-plus story buildings made of timber, close to Toronto's central business district, as part of their commitment to sustainability.

Sustainability is a "key factor" in evaluating the proposal, said Andrew Tumilty, spokesman for Waterfront Toronto, the government-mandated agency in charge of the Quayside development.

The issue typifies the multitude of challenges Sidewalk faces in getting its smart city off the ground - including governmental regulations that are years behind current technology, and a shrunken geography for the project that brings into question the viability of many of their proposals.

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