PNB Housing Finance today said it proposes to raise USD 1 billion (about Rs 6,500 crore) through external commercial borrowing window to fund business expansion. The board in its meeting held today has approved to raise the funds by way of external commercial borrowings for not exceeding USD 1 billion, PNB Housing Finance said in a regulatory filing to the stock exchanges. The fund would be raised in one or more trenches to augment its medium-term resources, it said. The company claims to be the fifth largest housing finance company with the asset under management of Rs 62,252 crore as on March 31, 2018. It offers housing and non-housing loans to retail customers. It also offers construction finance loans to real estate developers for residential housing.