Scotland’s Birkwood Castle and its surrounding estate, which was once home to a hospital for mentally disabled children, is to undergo renovations that will cost more than £7m (US$11m, €9m) – making it into a wedding, conference and special events destination with a wellbeing facility.

With an anticipated completion date of April 2016, Envestco – hotel and property developer – has confirmed that once planning is approved, work will begin on the phased mixed residential and commercial development of Birkwood Estate in Lanarkshire.

Once the castle is declared structurally secure, the building will be made wind and waterproof before visible repairs can be carried out to the castle’s roof and windows. Only then will the Grade B-listed building be converted into a high end 48-bedroom boutique hotel, to be operated by Envestco and Birkwood Estate staff.

The spa will be added to the property during the second phase of the redevelopment and will mirror its sister hotel’s Elemis spa at Peckforton Castle in Cheshire, which is owned by Chris Naylor – a director of Envestco. The spa’s installation will cost £2m and is set to be opened by Q2 2019. Architects Tony Naylor, Steve Jones & Ian Arnott are being considered by developers as the design consultants for the project. It is not yet known if the Birkwood spa will be supplied by Elemis too.

Open for members of the public as well as hotel residents, the spa will feature four treatment rooms, two couples’ suites, a swimming pool, steam sauna, experience showers, ice room, relaxation rooms, nail salon, retail boutique, spa café, gym and two fitness studios. Appealing to both men and women, the spa expects to offer anti-ageing and skin-specific facials, a variety of massages, wraps, hand and feet therapy, in addition to beauty treatments and men’s grooming therapies.

The transformation of the castle will be complemented by a residential development to the south east of the existing 86-acre site. Envestco recently added a further 38-acre plot to the estate called Abbey Green, which will host five brand new housing areas to be developed by Envestco’s subsidiary Redwood Homes. The first phase will see the construction of eight luxury four or five-bedroom detached homes. Further secluded plots will be transformed into woodland holiday chalets.

A brand new network of public footpaths are to be installed throughout the grounds, connecting the development to the local village of Lesmahagow.

Originally built in 1887 for the McKirdy family, the castle acted as a family home until 1920 when Lanarkshire Council purchased the property and made it into a certified Institution for Mental Defectives in 1923. After many extensions and the addition of a new wing in 1958, the hospital began to relocate patients in 2002 and officially closed in 2005 – making way for leisure developments.

The development represents a dynamic move for Envestco and Birkwood Estates. Both firms were established by two families and business associates – the award-winning hotel operator Chris Naylor – and Dan and Joanna Lloyd.

Naylor’s Peckforton Castle is a Grade I-listed Victorian hotel in the heart of Cheshire. After a £7m (US$11m, €9m) investment in this property, the hotel hosts 200 weddings a year and has turnover now exceeding £6m (US$9m €7.5m) annually.