Interiors: Planasker Old School, Marbhig, Isle of Lewis

It seemed Martin and Heather Malcolm's quest to become owners of a derelict 19th-century school was destined to be a failure. The couple moved to the Outer Hebrides from the mainland 17 years ago when Heather, who is from Lewis, took up a teaching post there. Martin immediately began searching for a renovation project that would provide them with a home.

While being shown around an abandoned croft he spotted a building on the edge of a nearby loch that looked more interesting. The ruined school hadn't been used since 1973, while the adjacent schoolmaster's house had lain empty since the 1950s. Curiously, nobody seemed to know who owned the place.

Martin's investigations alerted local council officials to the fact that money had never changed hands on a previously proposed sale.

"The council still owned the school," says Martin.

The couple endured a year-long wait as their purchase request passed through seemingly endless committees. A huge blow was delivered when the council placed the property on the open market and a buyer who wanted to knock it down to build an outdoor centre beat Heather and Martin's bid.

Dejected, the couple were on the verge of buying another property when they got an unexpected call.

"The buyer dropped out when they realised that the school's listed status would hinder their plans," Martin explains.

The couple signed title deeds the day before their wedding in 1994. Initially, Martin concentrated on turning the schoolmaster's house into a family home; when they took it on it was open to the elements and in a terrible condition.

Their vision for the finished project was in harmony with the school's protected status. A local building company was hired and features such as sash-and-case windows were reinstated in their original style, while the Traditional Rooflight Company supplied iron roof lights rather than modern Veluxes.

After moving in, the couple renewed their energy and funds before transforming the school into guest accommodation. By now Martin felt more confident in his building skills, and rather than hire a contractor, he took on tradesmen only as he needed them.

The job had its entertaining moments. Comments etched into old roof rafters in the 1870s by the original builders from Skye complained about the "dry" nature of the area.

"They weren't talking about the weather," laughs Martin. "This was a very strong Presbyterian community."

The school once accommodated 100 children in two large classrooms. Martin was determined to retain the proportions of one classroom, preserving the feeling of being in a school, and this is now the lounge/dining area. Elevating the ceiling allowed for the insertion of a gallery to its roof space.

"Visitors have this area to themselves," says Martin, explaining that Planasker is somewhere between a B&B and a self-catering arrangement. While there are no cooking facilities (the couple provide breakfast and, when required, dinner) but the accommodation is entirely private.

In the little entrance porch, original coat hooks and sinks remain at children's height, while the other classroom was divided to create a master bedroom, study and shower room. Another bedroom and bathroom are located above this second classroom but, with four children, the couple reclaimed these for family use, with access from their home.

"Planasker appeals to couples but additional guests can sleep in the gallery," Martin explains.

He took the building back to basics and even dealt with electrics, assisted by his father (an electrician to trade).

In the lounge Martin opened up a small hearth and commissioned an Edinburgh-based firm to make the stone fireplace, incorporating carved thistles. "I have a thing for thistles," says Martin, who was inspired to create these by a design he found on some old book spines.

Thistle motifs also appear on an etched panel for the window in the shower room and stained glass door panels, custom- made by a craftsman near Inverness.

The couple wanted wood finishes, including door frames and architraves to complement a Brazilian mahogany staircase. However, there are restrictions on importation of this timber and the arrival of Martin's order was badly delayed – in part by a poisonous snake found on board the cargo ship. A local joiner used the mahogany to create the gallery and panelled ceiling as well as the study's panelled walls. Martin made the hearth in the study, where there's now a cast iron stove, created using slate found in the school's extensive garden.

It took days to remove Formica floor tiles laid during the 1970s – a horrible job as the adhesive was extremely strong. Some old floor timbers were salvaged for use in the bedrooms while the lounge and library were fitted with Meranti, a hardwood that looks a lot like mahogany. For the porch the couple managed to source period-style tiles.

The couple often travelled to the mainland to scour architectural salvage yards. Martin obsessively sourced period details such as Bakelite light switches and was delighted to find The Edina Lock & Key Company, an Edinburgh-based supplier of traditional door fittings.

Period-style radiators are reproductions, their immense weight making for grumpy deliverymen. And after driving to Stirlingshire to collect the staircase from a farmer who had offered to bring it this far north, Martin was glad when it (only just) fitted through the windows in two pieces. Its posts are inspired by cast iron thistle designs Martin admired in Glasgow's Central Station.

During the period of decorating, scaffold was required so Martin could oil every piece of wood. The couple took time sourcing period-inspired wallpapers by Sanderson and Victorian-style tiles for the shower room.

Much of the furniture and pieces such as the piano and spinning wheel came from a croft owned by Heather's uncle, and antique shops revealed treasures such as the school desk in the porch. The sole original item left in the school, a jotter cupboard, is now a linen store. Appropriately, the couple chose traditional Harris tweeds, bought in a since-closed local mill, for curtains and cushions, which guests love. Of course, the tranquil setting is also a huge hit with visitors. What could be nicer than collecting Martin and Heather's picnic hamper, filled with gourmet Scottish products, for a boat trip on the loch, before returning to the haven of Planasker, a perfect lesson in relaxation if ever there was one?

Planasker Old School, Marbhig, Isle of Lewis (01851 880476, www.planasker.co.uk)

• This article was first published in The Scotsman Magazine, April 17, 2010