It's every homeowner's worst nightmare.

Eastern Daily Press: Police and the fire service at Neil Harrison's house on Finkelgate on Christmas Eve, 2010. Photo: Denise BradleyPolice and the fire service at Neil Harrison's house on Finkelgate on Christmas Eve, 2010. Photo: Denise Bradley (Image: ©Archant Photographic 2010)

Subsidence - when ground below a house collapses or sinks, taking the foundations with it - can, to put it mildly, cause a headache, costing thousands of pounds to fix and leaving owners homeless.

For Neil Harrison, 62, it was on a snowy Christmas Eve in 2010 that his nightmare began, with what initially appeared to be an innocent effect of wintry weather at his Finkelgate home.

"That night, or around that time, a water main had burst outside the road," he said, "which started the clock ticking. I had no idea. I went to work, no problem, came home early as it was Christmas Eve, opened the front door and it was sticking.

Eastern Daily Press: Police and the fire service at the end of terrace house in danger of the gable end collapsing at Finkelgate, Norwich, on Christmas Eve, 2010. Picture: Denise BradleyPolice and the fire service at the end of terrace house in danger of the gable end collapsing at Finkelgate, Norwich, on Christmas Eve, 2010. Picture: Denise Bradley (Image: ©Archant Photographic 2010)

MORE: Demolition completed of house that sunk around 30cm in Finkelgate, Norwich

"I didn't panic - sometimes it happens if they get wet, I didn't think anything of it."

He sanded the wood down, but found, later, that the door was still sticking. Then the problem worsened. Fast.

Eastern Daily Press: July 13, 2011 - It’s a saga which has been dragging on now for more than six months. Since Christmas Eve last year, Finkelgate, a vital road leading in and out of Norwich city centre, has been closed to traffic.July 13, 2011 - It’s a saga which has been dragging on now for more than six months. Since Christmas Eve last year, Finkelgate, a vital road leading in and out of Norwich city centre, has been closed to traffic. (Image: Archant)

"I saw a crack all the way to the top of the house," he said. "At this point I was thinking 'this is not good', if it's happening that quick it's something serious. By about 4pm it was much bigger, and a brick came out."

With Christmas fast approaching, his home insurer's office was empty, so he rang the fire service.

"Within minutes a massive team arrived and the whole road was closed off," he said.

He said the location of the house - on a busy thoroughfare, with no garden - and the danger of it collapsing onto pedestrians expedited the response, with firefighters quickly working to shore up the house.

Eastern Daily Press: The end terrace house on Finklegate. Picture: Nick ButcherThe end terrace house on Finklegate. Picture: Nick Butcher (Image: Archant © 2010)

"They decided the house was unsafe to enter, but I had about five minutes to get phone chargers and things," he said. "I'd already arranged to stay with my sister over Christmas."

Despite the high stakes, Mr Harrison, who now lives near Kerrison Road in Norwich, kept calm.

"I only had to worry about myself, and it was only a house at the end of the day," he said. "My friend had recently been diagnosed with cancer, and I thought 'what would I rather have?'"

Eastern Daily Press: Neil Harrison back at Finkelgate at the now empty plot (behind the metal fence) where his end of terrace house collapsed on Christmas Eve nine years ago. Picture: DENISE BRADLEYNeil Harrison back at Finkelgate at the now empty plot (behind the metal fence) where his end of terrace house collapsed on Christmas Eve nine years ago. Picture: DENISE BRADLEY (Image: Archant)

MORE: Damaged Finkelgate house could be demolished

The next three months were spent in the B&B, without cooking or washing facilities, as he tried to look for a property to rent while the claim was sorted.

"I was frustrated at this point," he said. "I needed to find a place because I had possessions back but there's no market at that time of year.

Eastern Daily Press: Neil Harrison back at Finkelgate at the now empty plot (behind the metal fence) where his end of terrace house collapsed on Christmas Eve nine years ago. Picture: DENISE BRADLEYNeil Harrison back at Finkelgate at the now empty plot (behind the metal fence) where his end of terrace house collapsed on Christmas Eve nine years ago. Picture: DENISE BRADLEY (Image: Archant)

"Plenty were too expensive for the insurance company, and I was told I didn't earn enough to rent some, which was crazy [as the insurance provider was paying]."

He later moved into a flat at Albion Mill, as surveys continued and later found that a water leak had washed away the foundations to the front and side of his home. Mr Harrison, who works at Sprowston Community Academy, was left in limbo.

"No-one could really make a decision," he said. "By this time it was Christmas 2011, and my landlords decided to rent my property to someone else to make more money."

Finding himself homeless again at Christmas, he raced to find a new property and eventually settled in Morgan House on Rouen Road.

Eastern Daily Press: A bus which fell into a sinkhole on Earlham Road, Norwich in March. Picture: Archant archivesA bus which fell into a sinkhole on Earlham Road, Norwich in March. Picture: Archant archives (Image: Archant)

MORE: Finkelgate land sells for five times guide price in auction

But about two years later - again, in December - he received a confusing message from his estate agents confirming that he had given up his house. His insurance company had decided to close the claim, without telling him.

Eastern Daily Press: Working on a boring at subsidence behind houses on Merton Road, May 1936Working on a boring at subsidence behind houses on Merton Road, May 1936 (Image: Archant)

And a clause in his policy meant Mr Harrison, who had lived at Finkelgate for 25 years, would only be paid a fraction of the total cost of the work.

It limited the cover for costs of debris removal and demolition to just 10pc - and with his house having to be demolished, the bulk of his claim fell into that 10pc. He would have had to insure the house for almost £1m to cover the cost.

But he took action, signing up to consumer website Money Saving Expert over Christmas, posting about his story and gaining enough traction that it stayed on the platform's home page for a week - and sparked a call from senior management.

Weeks later, he received his first bit of good luck since 2010 - confirmation the full claim would be covered, along with his extra costs.

Eastern Daily Press: House subsidence on Gertrude Road, Norwich. Darren and Rachel Mildon, who were neighbours to the subsiding house. Picture: ANTONY KELLYHouse subsidence on Gertrude Road, Norwich. Darren and Rachel Mildon, who were neighbours to the subsiding house. Picture: ANTONY KELLY (Image: Archant Norfolk 2016)

Even today, Mr Harrison remains positive, though admits the treatment of him during the claim was "horrible".

"The key bit is that it's just a house," he said. "I had to keep things in perspective. I would rather my house fall down than being ill or anything serious. It can happen to anyone."

MORE: Finkelgate saga comes to an end in Norwich almost two years after house started subsiding

Eight months wait for couple

After subsidence struck, one couple were forced to wait eight months before they could move back into their home.

In January 2016, houses on Gertrude Road were evacuated after subsidence caused by a burst pipe underground left four terraced homes uninhabitable.

Among the owners were Rachel and Darren Mildon, who, after being evacuated, were forced to stay with family outside Norwich as they tried to find a temporary home - which proved tricky with their pets.

Eventually, it took eight months before the couple were able to move back into their property in August, though repairs were still needed at that point.

It wasn't until the start of September that the work was completed and workmen left the house - just days before their wedding.

They sold their home the following year, to move elsewhere.

When the houses were first evacuated, a neighbour set up an online fundraising page to support the affected families.

Signs of subsidence

Problems with subsidence in Norwich are well-known.

The photograph of a double decker bus in a hole on Earlham Road, taken in 1988, has become iconic, while the city's underground network of tunnels and chalk mines has led to problems.

In 2016, Plantation Gardens was closed for weeks while sink holes were investigated.

And in 1936, an 80-foot sinkhole swallowed three homes on Merton Road, claiming the lives of two people.

But what should you look out for? According to the Homeowners Alliance, the signs include:

- A crack that's wider than 3mm, visible on both the outside or inside of your home, often diagonal and usually wider at the top than the bottom

- It may be located close to a window or door

- Doors and windows that stick

- Signs of rippling in wallpaper at the wall and ceiling joints