As winter settles over Gaza and the rains begin, displaced families are struggling to keep their makeshift shelters from collapsing.

As cloudy skies threatened another downpour in Gaza city, Abdel Rahim Halawa, a father of seven children, worked to fasten a tarp over his shelter, made of some pieces of wood, blankets and worn sheets of plastic.

Lines of clothes were hung in the wind near structures surrounded by mounds of debris.

"Tonight, all the mattresses and blankets got drenched, and I bought nylon to protect us from the rain and alleviate our suffering," Halawa said.

"We don't know how we'll survive if winter comes."

Some have taken shelter in what remains of destroyed buildings.

One family has been living inside a section of concrete held up by a single crooked column, its open side covered with a piece of tarp.

"It's on the verge of collapse. Engineering committees came and said it's forbidden to live in this house, but we have no alternative. Where else can we go? Especially in the winter and the bitter cold," Saed Salhi said.

Salhi is living in the structure with four members of his family, who are displaced from Jabaliya in northern Gaza.

After relentless Israeli bombardment, entire neighborhoods have been reduced to rubble, streets are unrecognizable and once-bustling markets are now just twisted metal and concrete.

The U.N. development agency says the amount of debris in Gaza would be enough to build 13 giant pyramids in Giza in Egypt.

The latest joint estimate from the U.N., the European Union and the World Bank is that $70 billion will be required to rebuild Gaza.