Lofchik J. in Grayling v Haldimand (County) [2014] O.J. No 239 summarizes that the 3/4 of an inch rule is the starting point for the city being at fault:
43 Even though a state of perfection is not expected, the Ontario Court of Appeal appears to have established some bench marks as to when sidewalk elevations become non-repair. In Ford v. City of Windsor,[1955] OWN 873, the court ruled that a height differential between three-quarters of an inch and one inch constituted a non-repair. Similarly, in Daley v. Toronto, [1960] O.W.N. 480, the court found that a height differential no greater than three-quarters of an inch was not a non-repair. Therefore, as Valin J. noted in his review of these cases in Blaqiere v. Burlington [1999] O.J.No.2558 (Superior Court) at para 16, three-quarters of an inch appears to be “something of a judicial rule of thumb”. (See also Epifano v. Corporation of the City of Hamilton,[2055] O.J.No.1463 (S.C.J.), para 9 and Boyce v. Woodstock [1993] O.J. No. 2532, at para 32.
