Four of Nonthaburi's six districts were inundated: Bang Bua Thong, Bang Yai, Bang Kruai and Sai Noi.
"Bang Bua Thong and Bang Yai had the largest amount of low-rise damage," said Samma Kitsin, director-general of the Real Estate Information Center.
Of 19,166 complete units in the province, 5,425 were in Bang Bua Thong and 5,053 were in Bang Yai, more than half the total.
The absorption rate of low-rise units in Nonthaburi in the second half of last year dropped to 1.6% from 5% in the first half.
"If this rate continues, then it means the total supply will take up to three to four years to sell, up from the usual 20 months," said Mr Samma.
However, Kree Dejchai, the chief operating officer at SC Asset Corporation Plc, said the company's housing sales in Nonthaburi during the first half were 70-80% of their usual rate and are expected to return to normal in the second half.
"Positive factors include the Purple Line mass transit, which should start operating by 2015, a new bridge across the Chao Phraya River, universities relocating to the province, and Bangkok's new city plan that will drive people to seek a house in Bangkok's outskirts," said Mr Kree.
During the first six months of the year, 15 low-rise projects launched in Nonthaburi with 2,355 units, mainly in Muang and Bang Kruai districts. But only 368 units were booked, or 16%, below the usual 20-25%, said Mr Samma.
The absorption rate of condos in the second half of 2011 was better than that of low-rise units. Most condos are located in Pak Kret and Muang districts and thus spared some the flood's fury.
During the first half of the year, eight condo projects were launched with 6,230 units, mainly in Pak Kret and Muang districts. Some 56% of units were booked.
Research showed 45,900 residential units in Nonthaburi at the end of 2011. Some 34,300 units were low rise from 160 projects worth a combined 126.3 billion baht, while 11,600 units were condos from 21 projects worth a combined 21.1 billion.
Of the low-rise units, 19,500 worth 68.08 billion baht were sold. Some 14,800 units worth 58.2 billion remain.
Of 11,600 total condo units, 6,800 units worth 11.6 billion were sold, leaving 4,800 units worth 9.5 billion on the market.