My father’s death from pneumonia on 1 January 2012, aged 81, was almost a relief. He had been diagnosed with vascular dementia two years earlier, but remained reluctant to accept help with personal care, even as he forgot how to fasten his own belt and that you don’t drink whisky with breakfast.

After Dad’s death, I moved into his home to clear it. The mammoth size of this task soon became apparent.

The word “hoarder” is loaded, conjuring images of people trapped by mountains of yellowing newspapers. Dad’s house, while undoubtedly cluttered, still functioned as a home. I have no doubt, however, that he suffered from a hoarding disorder, concealed by the luxury of space.

My father, Andrew Kopec, spent his last 30 years in the same five-bedroom house in Whitchurch Hill, Berkshire. It had an attic, four sheds, two garages and an outhouse. Dad had filled it completely. He had kept 50 years’ worth of water bills, work diaries stretching back to 1962, reports from every bridge, dam and sewer he had worked on as a civil engineer, every payslip.

Wardrobes bulged with 70s suits and battered desert boots. Tea chests of African carvings from periods working abroad sat alongside boxes of Pyrex kitchenware bought when he and my mother, Anne, were newlyweds.

These items held little value and had not been touched in years. Why had he kept them all?

When I was growing up, Dad was strict, with mealtimes particularly fraught, as any suggestion of wasting food made him furious. A grain of rice left on a plate would be enough to spark his temper. “There are people going hungry,” he would bark.

Every berry had to be harvested from our garden, every chestnut collected from local fields. Mum carefully meal-planned to use up leftovers and avoid Dad’s ire. Only when he was working away could we relax, enjoying pizza and oven chips from our laps.

We never questioned the way Dad was. He certainly didn’t talk about his feelings or his own childhood.

When I was 18, Mum told me they had once watched some children running to embrace their father in an airport. Apparently, Dad said: “I wish I could do that.”

I was surprised. I had only ever seen him be tactile with the family dogs.

After Dad retired, Mum hoped to downsize and tried to clear the house. But getting Dad to part with anything was a struggle, every item leading to a two-hour discussion. “We paid good money for that,” he would argue. Or: “This will come in handy one day.”

Dad’s Mercedes, which had once represented him having “made it” professionally, sat rusting on the drive for years after it stopped running.

Mum took to subterfuge. Whenever Dad went sailing, she would offload piles of paperbacks to the charity shop or sneak out old potties and cots from the attic. “We won’t tell your father,” she would say.

Mum never got to complete her mission. In August 2004, doctors found two tumours, each the size of a tangerine, on her brain. Just six weeks later, she was dead. Mum had always acted as a gatekeeper for Dad. Her death meant I got to know him more.

A year after we lost Mum, Dad gave my younger sister, Juliette, and me a folder. He had found the paperwork after Mum’s death an ordeal and wanted to be prepared for his own demise.

Jo Cooke’s father, Andrew Kopec. Photograph: Courtesy Jo Cooke

As well as meticulous financial records and directions for his will, Dad’s “postmortem” plan contained instructions on cancelling the milkman, which coffin to choose and what clothes he would wear to his funeral, as well as which papers should carry his obituary. Dad always wanted things done his way. Micromanaging his own death was unsurprising.

As he handed over the folder, he laid down another rule: no one was to touch his things until he was gone. “Don’t meddle until I’m in the ground,” he insisted.

Any movement of things from the house had stopped with Mum’s death anyhow. “Why are you touching that?” he would snap if you did try to help. “Leave it!”

It was a couple of years before he died, when my daughter, Sasha, interviewed him for a school project, that we found out why Dad was the way he was.

He described the terrible hunger he had endured, first in Germany, where he was born in 1931, and then in Poland. He recalled his parents sacrificing food for him and told how, in 1939, aged just eight, he and his mother had fled the war, seeking refuge in Kenya. Dad’s father, a lawyer, stayed behind to help with the war effort.

Although my grandfather survived the war, the separation marked the end of my grandparents’ marriage, and Dad didn’t see his father again for another 10 years. They met just once more, when Dad moved to England to go to university, aged 18. My grandfather was by then living in Southampton, but the meeting failed to rekindle a relationship and they were not in touch when my grandfather died in his 50s of a heart attack.

Hearing Dad’s story made lots of things fall into place. But, like my mother before me, I simply found ways to avoid provoking him. When Juliette and I cleared out-of-date food from his fridge one Christmas, we drove to the local working men’s club to use their bin, escaping a long lecture had Dad spotted the transgression at home.

It was soon after the revelations to Sasha that Dad’s memory started to go. He became unable to drive and his moods darkened. Concern was growing about his future when he died.

I felt my job as a civil servant made me best placed to manage Dad’s estate. I’m naturally organised and am used to dealing with bureaucracy.

Sasha, then 15, and I moved in and every evening after work I would tackle Dad’s clutter. At weekends, my four siblings, including two from Dad’s first marriage, would come round to make any joint decisions.

Very early on, my half-sister Cynthia questioned why I was binning a packet of unopened denture tablets. “If we debate every item, we will be here a while,” I suggested gently.

Dad’s things provided a timeline of his life, and I dealt with my grief as I dealt with his belongings: the maps of Poland too outdated to be of use, the two complete sets of encyclopedias, the endless bags of computer cables, the two large skips of metal waste from the garages.

Why had he felt that he needed five hole punches and enough pencils and labels to keep a small business going for years?

He had never struck me as sentimental, yet he had kept all his mother’s letters, and even notes from us as children: one a heartfelt plea from Juliette, written during an outbreak of myxomatosis, that Dad not shoot any more rabbits.

Dad was more self-aware than I had realised, too: one computer password was “grumpynet”.

It took almost five months of bonfires and trips to charity shops and the tip before the house was empty. I had done it. Dad’s children were all still speaking, too.

It was a lightbulb moment for me. Sasha and her brother Sam, then 17, needed me less and I wasn’t enjoying my job at the Department for Education. I took voluntary redundancy and set up as a professional declutterer.

My first client was a downsizing retiree, but it wasn’t long before chronic hoarders were getting in touch. I began to recognise common behaviours: the overthinking and distress at the thought of letting go of objects, the paralysis of indecision. I learned how hoarders often use objects as emotional insulation or to fill a void.

Dad’s childhood deprivation and the sudden loss of his home and father at just eight were obvious triggers for him. Had Mum lived and persevered with her downsizing plan, I believe it would have provoked a crisis.

In 2014, I set up Hoarding Disorders UK, a community-interest company, with Amanda Peet, a practitioner of Emotional Freedom Technique, a tapping therapy.

In addition to private clients, we take referrals from social services and I also run two hoarding support groups near my home in Thatcham, Berkshire.

My experience has made me acutely aware of what I will leave for my own children to tackle after my death. With this in mind, I recently shredded paperwork from my divorce in 2004. The kids won’t want to read it and, when it comes down to it, it’s just clutter.

• Understanding Hoarding by Jo Cooke (Sheldon Press, £9.99). To order a copy for £8.49, go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.