Thousands of Toronto's social housing units may soon be boarded up as the buildings age faster than they can be repaired.

The Toronto Community Housing Corporation (TCHC) said several units have been closed down, and entire buildings may be shuttered as a result of lack of funds.

"We have to close them down because we can't let people live here," TCHC CEO Greg Spearn told CTV Toronto during a tour on Thursday.

CTV's Natalie Johnson got an exclusive look at one building, where whole floors have been closed due to disrepair.

The roof of the apartment building at 415 Driftwood Ave., near Jane Street and Finch Avenue, is 50 years old, and water has been seeping in for decades.

The windows leak, and mould and water damage have caused all but three units on the 17th storey to be closed.

"In essence, the 17th floor has become the roof for the 16th floor," Spearn said.

As the water continues to seep down the building, more units will have to be boarded up floor by floor.

Across the TCHC system, approximately 400 units are currently inhabitable, but the TCHC estimates that that number could jump to 7,500 in the next few years without more capital money.

"My worst nightmare is having to come to a family and say, 'Look, the three-bedroom town(house) you're in is no longer habitable,'" Spearn said.

He said the threat of having to board up units has become so real that in many cases, tenants have stopped reporting major issues and damage. The tenants are worried that if the problems can't be fixed, their homes will be boarded up and they'll have nowhere to go.

"Where would I go? I have no idea. I have no family. I would have nowhere," tenant Margaret Cantwell told CTV.

"I don't know what the answer is, and that's why it's my worst nightmare," Spearn said.

The TCHC is hopeful that the province and the federal government will come forward with additional capital funding before it needs to shut down more apartments.

With a report from CTV Toronto's Natalie Johnson