A nonprofit founded in honor of an FDNY firefighter killed on 9/11 made good on a pledge Tuesday to pay off the mortgage of a fallen Inwood fire chief.

“You’re not going to have to worry about your mortgage payments anymore,” Frank Siller, head of the Stephen Siller Tunnel to Towers Foundation, told the family of Joseph Sanford Jr. at their Davis Avenue home in Inwood.

Sanford, 43, was critically injured in a Dec. 19, 2014, fire at a Woodmere home that was under construction.

He was found facedown in up to 18 inches of water, partially covered by a piece of furniture that had been moved by other firefighters to cover a hole on the first floor caused by the blaze.

State investigators have not said whether Sanford fell through the hole or was hit by falling furniture when he went down into the basement.

He died on Dec. 23, 2014, of complications of a near-drowning, according to a state report issued in the investigation of his death.

Sanford’s widow, Jacqueline Scott-Sanford, who stood arm-in-arm with the couple’s daughter, Janisha, thanked the foundation and Bank of America, which held the mortgage.

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“This is a huge burden that has been lifted off of us, and to know that our family has a home forever,” Scott-Sanford said.

The nonprofit on Tuesday presented Sanford’s widow with a mortgage-free letter. The foundation declined to say what the mortgage balances was, but had said it hoped to raise at least $300,000.

White Christmas lights hung from the top of the beige one-story home, which was renovated after Superstorm Sandy dumped four feet of water inside. Red bows decorated a white fence.

Sanford’s widow said she and her late husband had been married for more than 22 years. They bought the home in 2007 after a two-year search.

“Family meant everything, to have our home with our children,” she said.

Her husband would flop into his favorite white leather chair, in the corner, by the door, and hoist his feet onto an ottoman to watch Yankee games with the lights off, she said.

A former assistant chief, her husband was a 17-year veteran of the department. He was posthumously promoted to chief.

Members of his department attended the ceremony. Two Inwood trucks hoisted a massive U.S. flag at an intersection near the home, and more than four dozen flags lined the street.

“In the season of miracles, maybe this is the biggest miracle,” said the family’s Garden City attorney, Christopher McGrath, who grew up nearby and first reached out to the foundation.

“This has never happened for a volunteer firefighter who passed away in the line of duty.”

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Sanford’s wife said she planned to have friends and family over on Wednesday, the anniversary of her husband’s death.

“We’re going to celebrate life and figure out how we’re going to move forward,” she said.