Property Taxes Valleys of Thornhill By MeisterMarch 9, 20170 Back to Home Hi Bram, As you know we have started looking for a house in the Valleys of Thornhill. What is the average property tax for a detached home in the 2500 to 300 sq foot range. Answers By Bram SandowMarch 9, 2017 12:29 PM Detached homes in the Valleys of Thornhill in and around 2500 - 3000 sq ft had property taxes bills of approximately $7,000 in 2016. Back to Home