Christa Liedtke, 75, decided to sell the half-timbered house near Cologne three years ago, after she began to find the steep stairs too much to handle.
She fell in love with the house in 2005 and poured thousands of euros into renovating it. "As soon as I saw it, I knew it was the one," she said. “In 2011 I wanted to sell it, with a heavy heart, and that’s when this all started.”
Local authority officials told her she had to pull it down because there was no planning permission to build the house in the first place.
Irmgard Mertins, widow of a Jewish banker murdered by the Nazis, had built the house in 1939, as a place to wait out the war. In the chaos of war she failed to apply for all the right paperwork.
Legal cases turning on the absence of key permission, and documents lost, falsified or destroyed during the war are quite common in Germany. They sometimes leave homeowners realising with dismay their wartime-built houses do not have valid planning permission.
"In the last eight years we have seen six such cases," Birgit Bär, a spokeswoman for the district authority Rheinisch-Bergischer Kreis told The Local.
She said in the aftermath of the war many small buildings were converted into flats to cope with the sudden housing shortage due to bomb damage - and very few of the new landlords bothered to secure building permission for the new properties.
When Liedtke and her daughter bought the building - paying €250,000 for it in 2005 - they were not made aware of the missing paperwork.
And Bär says the letter of the law must be followed in such cases.
"Entry in the land register is just proof of ownership of the property, not of permission for a building, and for that reason the relevant laws must be exercised," she said.
"We can't just close the book on this one because she's so nice."
Bär agreed the demolition order was a regrettable outcome, saying her office had explored all the legal alternatives, and had even offered Liedtke a special permit to continuing living in the house.
"Of course it's not sensible to demolish it completely; no one wants to do that," Bär told The Local.
"But we have to do it, because German building law is very clear on this point. Houses outside of built-up areas with no planning permission have to go."
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Bär said her office wanted to see a new law requiring an expert notary to be involved in house purchases, to spare people buying buildings they will later be forced to have pulled down.
But she added: "We are grown up people, we are responsible for what we sign our names to. Absence of important documents should always ring alarm bells."
Liedtke's appeal against the demolition order is to go to the region's higher administrative court in Münster, but a date has not yet been set.