The main acquired property has 53,000 square meters of rental space in the Midtown Toronto business district.
Afcon's share price fell 20% in the previous five trading days after the company reported a NIS 25 million third quarter loss.
The buyer intends to convert the listed building, in a central Jerusalem location, to a hotel.
As construction company shares peak, current trends indicate steep price rises in 2020.
Although WeWork is laying off thousands of employees worldwide, it seeks to expand in Tel Aviv.
The sale is aimed at increasing liquidity and avoiding a going concern warning for IDB.
CEO Eyal Lapidot unveiled his strategy for the coming years: "Shikun & Binui has a great deal to do, and a great deal of value to create."