Civil and structural engineering firm Will Rudd has reached a topping out benchmark on a nine-storey extension at the Category A-listed Caledonian Hotel in Edinburgh.

The development for client Klarent Hospitality and principal contractor Edgewater will add 96 guest rooms to the property. The project increases the hotel capacity by 30% alongside upgrading servicing and back-of-house infrastructure.

Built over the former Princes Street Railway Station footprint, the constrained site required complex engineering. The team installed deep piled foundations and reinforced concrete ground beams to support the extension around an active brick sewer.

Above ground, the engineers used light gauge steel framing over a steel brace frame and concrete basement structure. A double-span beam design reduced structural steel requirements, lowering construction costs and cutting the carbon footprint.

The project forms part of three city-centre hospitality developments delivered by the firm in Edinburgh. Between Princes Street and Rose Street, the business is providing design services for RIGH Properties on a new 60-bedroom luxury apart-hotel.

The Princes Street project involves partial demolition and re-framing of three buildings, including internal strip-out work within the Category B-listed 71 Princes Street. The firm is also providing structural engineering services for a 24-bed extension to RIGH Residences at 71 George Street.

Stuart Fleming, director at Will Rudd Edinburgh, said: “Edinburgh’s hotel sector has consistently proven to be one of the UK’s most resilient and dynamic markets. As demand for quality accommodation grows, unlocking potential in the city centre increasingly relies on smart engineering that can navigate complex, heavily constrained gap sites and adapt historic building stock.

“Reaching the topping out stage at The Caledonian Hotel is a testament to the collaborative effort of the entire project team. From navigating legacy railway foundations and active utility networks at Princes Street to threading modern steel frameworks through heritage buildings on Rose Street and George Street, our focus remains on lean, precise engineering that safeguards Edinburgh’s built heritage while delivering commercial value for our clients.”

Speaking to Hotel Owner regarding Will Rudd’s approach to the project, a spokesperson said: that the “defining challenge” was to design foundations and substructure that were “efficient and buildable, within an extremely tight, heavily constrained site, and to protect and preserve historical structural elements of the hotel, and archaic remains of the old Princes Street Station”.

They added: “Further, a main historic brick sewer runs very close to the footprint of the extension and this key piece of public infrastructure needed significant exploration, precision of surveying, and a refined foundation proposal to protect this, without compromising the layout and additional capacity that the extension delivered.”

Regarding their wider work in the Edinburgh hotel sector, and this project’s impact on this, they said: “This project presents the latest in a long line of hotel projects that Will Rudd has delivered in Edinburgh, and the accumulation of expertise, experience and creativity built up over years. This has been brought to bear, to deliver additional hotel capacity, to one of Edinburgh’s Heritage gems. This showcases Will Rudd’s understanding of the engineering parameters associated with the Edinburgh New Town and the properties and considerations of building in extremely close proximity to historic structures and infrastructure.”