A glacier collapse on August 26 sent a deluge of ice, rock and mud sweeping through the impoverished country's border region with China, wiping out settlements and villages and leaving few houses standing and undamaged.
"Our preliminary estimates are that 7500 houses have been completely destroyed, either washed away or buried under debris and mud," Dharma Raj Upreti, chief of the National Disaster Risk Reduction and Management Authority, told Reuters.
Even houses still standing were not habitable, Upreti said, with authorities estimating that about 20,000 would have to be rebuilt in different, safer locations.
"We anticipate that the resources required for rebuilding will be substantial," Foreign Minister Shisir Khanal told foreign ambassadors in Kathmandu.
At least 1252 people were killed in Nepal last week as houses, streets and schools in towns and villages near the border with China's Tibet were swept away.
More than 4200 people are still missing and thousands more displaced.
China has put the death toll in Tibet at 21, with 541 others listed as missing.
Prime Minister Balendra Shah's cabinet set Monday, the 13th day after the disaster, as a day of mourning in Nepal, a cabinet spokesperson said.
In Hindu tradition, the 13th day traditionally marks the end of the formal mourning period.
More than 9300 Nepali army troops were on the ground in the affected areas of Timure in Rasuwa, Nuwakot, Dhading, Chitwan and Nawalparasi East, co-ordinating search and rescue of the injured and helping with management of bodies, clearing blocked roads and providing emergency medical treatment, an army statement said.
An Australian medical student whose partner went missing near the Nepal-China border urged tech companies to do more to help find him and others caught up in the disaster by sharing tracking data that could narrow the search areas for rescue teams.
Sarada Viswanathan, 23, has spent the past eight days trying to piece together the last movements of her boyfriend Rishab Iyer and his family.
Viswanathan said obtaining information out of Nepal has been difficult, with Apple and Optus denying her requests for location data that could shed light on their whereabouts.
"We're all just scrambling to try and put the pieces together ourselves," she said.
"Their phones are most likely dead. They have no way of contacting us. We're really just begging for help."
Australia pledged additional support and said it would also share telecommunications data with Nepali authorities.
At least 583 foreigners were missing in the floods, Nepal said on Thursday, many of them pilgrims and trekkers. There are 36 Australians among them.
An army officer, who spoke on condition of anonymity as he is not authorised to speak to the media, said the search was continuing with experts from India, South Korea and China for at least 900 survivors believed to be trapped in the tunnels related to hydropower projects.
Army spokesman Raja Ram Basnet said two bodies had been recovered from the tunnel of Langtang Khola hydropower plant.
China has sent a third batch of aid to Nepal, including tents, blankets, medical protective suits and satellite communication equipment, the foreign ministry said, adding that the weather offices of the two countries were in contact with each other.
Authorities were working to restore regular routines as much as possible, with a focus on getting children into makeshift schools.
More than a week after the flood, at least 22,000 children urgently need safe drinking water, sanitation and hygiene support, UNICEF said in a statement.
"Our priority is to restore normal life. We are considering if children can be taught in the holding centres," said Phanindra Paudel, an official at Nepal's National Emergency Operation Centre.
