It has been built to house and service the majority of Toronto Transit Commission's fleet of Flexity Outlook light rail vehicles.

[3] While the existing Roncesvalles Carhouse and Russell Carhouse will house some of the vehicles, these older facilities cannot accommodate the entire fleet of Flexity streetcars, which are considerably longer than the Canadian Light Rail Vehicle/Articulated Light Rail Vehicle fleet.

[1] The TTC has been considering adding 60 more Flexitys to the current 204-car order to handle growth in demand and possible new streetcar lines along the Waterfront.

(A local complaint was that the Ashbridges choice would deny the community future additional parkland, and there were concerns about streetcar traffic on Leslie Street.)

Thus, an alternative was suggested to run the connecting track further east through the Russell Carhouse and via the industrial Knox Street to Lake Shore Boulevard.

TTC workers access the HVAC and propulsion systems, which are built into the roof of the low-floor Flexity Outlook vehicles, via overhead catwalks.

[1] The carhouse building has a north-sloping green roof, and a stormwater management pond at the east end of the yard to irrigate the rooftop plantings, a mix of alliums and sedums.

[23] Outside the facility walls, along Leslie Street and Lakeshore Boulevard, there is a linear park incorporating the Martin Goodman Trail, wide multi-use paths, grass, plants and benches.

[19] In June 2009, the Ashbridges Bay Streetcar Maintenance & Storage Facility (now the Leslie Barns) was projected to cost $345 million CAD,[6] but this did not include provision for soil removal and site remediation, nor for the connection track to Queen Street.

[24] On November 11, 2009, Toronto City Council chose the site for the Ashbridges Bay Streetcar Maintenance & Storage Facility at the southeast corner of Leslie Street and Lake Shore Boulevard.

In November 2012, the TTC decided to change the name of the carhouse from the "Ashbridges Bay Streetcar Maintenance & Storage Facility" to the more colloquial "Leslie Barns" at the request of the local community and councillors.

On January 28, 2015, Natalie Alcoba wrote in the National Post that the facility was expected to be almost empty when it opened later in 2015 because Bombardier had fallen far behind delivery of the new vehicles.

[32] Although the Flexity streetcars started operating out of the facility on November 22, 2015, the barns were still under construction and would not be fully occupied by the TTC until early 2016.