Business magnate Donald Trump has announced the closure of The Old Post Office building in Washington DC as the property undergoes a US$200m (€144.4m, £119m) redevelopment – from office space into a luxury hotel and spa.

The estimated date for completion of the 270ft tall (85m) post office’s transformation is late 2015. The Trump International Hotel, The Old Post Office will be a 270-bedroom hotel.

The hotel will feature a 4,000sq ft (372sq m) Mar-a-Lago Spa by Ivanka Trump, Donald Trump’s daughter. The Mar-a-Lago boutique spa brand is named after the company’s 1927 Palm Beach property – The Mar-a-Lago Club – located within 20 acres of landscaped gardens with ocean views.

The 114-year-old building’s pavilion and clock tower attract tourists because there is a 360-degree perspective of the city from the observation deck – but the attraction will close for approximately two years for construction, beginning on 1 May.

“The building itself, which is totally irreplaceable, is going to be brought back to far beyond its original grandeur,” said Donald Trump in a statement.

Colony Capital LLC, a private international investment firm, partnered with the Trump Hotel Collection to preserve the landmark building. The co-investors’ plan was selected by the US General Services Administration (GSA) in 2012 as the preferred project. Congress directed GSA to enter into a long-term lease for private-sector development and restoration when, in 2008, the building was found to have outlived its usefulness as a federal office space.

“Deciding to move forward with the redevelopment of this iconic property potentially will save millions in taxpayer dollars,” said Robert Peck, GSA’s commissioner of the Public Buildings Service.

Architects Beyer Blinder Belle, interior design consultants Hirsch Bedner Associates and historic advisor and preservation specialists John Cullinane & Associates will retain Romanesque elements of the property’s current structure. The hotel will also pursue LEED green building certification, which provides the framework for building and operating sustainable hotels.

In addition to guestrooms whose floorspace will average more than 600sq ft (56sq m), there will be two presidential suites located in the historic former offices of the postmaster general – spanning more than 3,000sq ft (279sq m) each.

Meeting space at the luxury facility will add up to 39,000sq ft (3,623sq m) and will include a 13,000sq ft (1,207sq m) grand ballroom.

The historic library, with its 25ft (7.6m) coffered ceiling will serve as a 3,500sq ft (325sq m) junior ballroom and the clocktower attraction – which draws as many as 1,500 visitors a day – will have its own dedicated entrance and an Old Post Office museum, exhibition centre and retail outlets. The clock tower houses the official US Bells of Congress – a bicentennial gift from England to celebrate the end of the Revolutionary War. Under an agreement with the Trump Organisation, the clock tower will remain publicly accessible when the hotel opens.

The post office was originally approved by Congress in 1880 and completed in 1899.