The castle, which could be more correctly described as a castellated house because it began life as a house, was nothing more than a skeleton when the Everards bought it.
As their son Zane explains, there was stonework and little else to the property.
"There were no floors, no roof, only stonework that was beginning to deteriorate from the top down," Zane recalls. "All the debris from the fire in 1921 was still there -- just rubble piled inside the walls.
"There were even trees growing inside the castle for the past 50 or 60 years," he adds.
Local builder and friend of the Everards, Michael Cleary, asked if they were interested in restoring the castle -- a job he was keen to be involved in.
"I had always wanted to see it restored but it is always very hard to project costings on a restoration project," explains Zane.
However, after consultation with conservation experts, the Everards decided to embark on the monumental task.
The project was slow from the off because the castle had to be restored in line with strict conservation guidelines.
The work kicked off with a massive clean-up operation, which involved clearing out all the debris and stripping back the building to the old plaster.
The painstaking conservation work included re-pointing all of the stonework and replacing the woodwork with local timber and handmade plaster cornicing on site.
A Leader grant of €70,000 and a further €10,000 from the Georgian Society were secured to help with the restoration.
"We had one of the head men from the Department of the Environment advising us, as well as other people," says Zane.
The work was a real labour of love for Michael and Joan, and they endeavoured to use local materials and local craftsmen at every opportunity.
The work took four years to complete and the residence behind the great oak entrance door is a credit to the painstaking efforts of all involved.
The castle consists of an opulent dining room, reception rooms and library, two kitchens and nine bedrooms.
Although the emphasis in Lisheen Castle is on the historical aspect, the facilities in the newly renovated property are modern, with eight ensuite bathrooms, central heating, broadband internet access and a modern, catering-standard kitchen.
Interior decoration was handled exclusively by Joan, who has a background in interior design and "an amazing eye for detail", according to her husband.
Joan's aim was to recreate the classical style of a Palladian house, while at the same time making it a warm and welcoming space.
Most of the furniture was sourced from antique shops and clearance sales from other old houses.
Some pieces were also sourced from Moyglare Manor when it was closed. However, one piece that has special history to it was a bench sold in a clearance sale at Lisheen Castle in 1890.
"My predecessors, some of my mother's family, bought the bench at the time and it has been in the family every since," says Michael.
Today, the castle is rented out to visitors on a self-catering basis. Business is mainly internet-based, with American guests accounting for most of the bookings, although Irish guests are common around the Christmas and New Year holidays.
Recent guests include an American court judge, who must have felt at home as he also farms 10,000 Holstein cows.
The castle caters for around 12-14 people and can command a fee of up to €5,000 a week during peak season, according to Zane, who manages the business.
"That charge would include everything from phone, heating, utility bills, provision of computer and internet access," he said.
Like every type of holiday accommodation, occupancy rates for the castle have been hit by the recession but there are still bookings coming in for next year. Future plans for Lisheen include using the stately home as a wedding venue.
"We get lots of enquiries about weddings but, at the moment, we don't have the facilities for it as there is no function room," says Zane.
"Perhaps we will look at the marquee option."
"There are also some stables and outbuildings that have not been done up yet," he adds.
"There are some opportunities there for maybe a gym/ exercise room, games room or some independent units."
In the meantime, Michael and Joan continue to run a dairy herd of 120 cows from Fortfield House. Michael is coy about the total cost of the works at Lisheen Castle, although he admits that he "could have bought another 100ac for the cost of restoring it".
However, he adds that the castle work did not involve the type of limits, quota, compliance or red tape that buying more land would entail.
The future of Lisheen Castle looks secure in the hands of its latest owners, who saw in the old ruins the opportunity of owning a real gem.