We live in Barrie, Ontario and have two 2-story homes on either side; our neighbours, that are home all day, have a clear view into our backyard. I’m unable to build a privacy screen out of lattice as per our city bylaw. Theres a 
rectangular plant bed that is 10 ft x 5ft on our deck along the lattice fence and I was thinking of raising the plant bed up 3-4 feet and planting some type of privacy hedging ie: cedars, yews. I read that emerald cedars do not thrive and provide a thick top hedge in Ontario as it would out West. Any advice/suggestions on how I can tackle this?
Hello and thank you for contacting Toronto Master Gardeners. You are very right about emerald cedars (Thuja occidentalis ‘Smaragd’) — they do well in the milder, damper climate of British Columbia but not so much here in Ontario, where winters tend to be colder and moisture levels can fluctuate. Due to their requirement for moisture, they are also difficult to maintain particularly in a raised planting bed, which drains faster than an in-ground planting bed.
It sounds like you are interested in something that will provide year-round privacy, so evergreens are indeed a good option. Some alternatives to emerald cedars that you may wish to consider include pyramidal cedar (Thuja occidentalis ‘Pyramidalis’) and black cedar (Thuja occidentalis ‘Nigra’). This factsheet from PennState Extension provides some useful tips for planting a privacy hedge, and offers a range of ideas for plant selection including both evergreen and deciduous trees and shrubs. Keep in mind that you should select trees and/or shrubs that are hardy in your region. Barrie is in Canadian Plant Hardiness Zone 5b, which is around USDA Hardiness Zone 4 (Canada and the United States have slightly different zone criteria). Also, you will need to pay extra attention to moisture levels in your planting bed. Applying a thick layer of mulch around newly planted trees and shrubs will help retain moisture and offset some of the moisture loss from the increased drainage of the planting bed.
You may also find some of these previous posts about privacy hedges on our Ask a Master Gardener page useful.