Any building project has its unique complexities and a project which includes renovation and refurbishment, new-build construction, and the implementation of a variety of sustainable and energy saving techniques, is no exception. But in the case of Harlech Castle in Gwenedd, Wales, the former had to be achieved in a building, next to a scheduled ancient monument, on a UNESCO World Heritage Site, in a conservation area on the edge of a Site of Special Scientific Interest (SSSI), within a National Park. A JCT Standard Building Contract With Quantities 2011 provided the contract solution.
Harlech Castle is regarded as one of the most important medieval castles in Wales and is a textbook example of the concentric castle design. It was built by Edward I as part of his campaign to conquer the Welsh principality of Gwynedd in the Middle Ages. The main structures of the castle were completed between 1283 and 1289.
Harlech belongs to a group of royal castles designed by Edward I’s chief architect and engineer, James of St. George. James of St. George’s designs rank amongst the most highly sophisticated and innovative examples of military engineering in Europe. Harlech boasts two rings of walls and towers, with an immensely strong east gatehouse. Impregnable from almost every angle, its secret weapon was a 200ft (61m) long stairway which still leads from the castle to the cliff base. In 1987, Harlech Castle was designated as a UNESCO World Heritage Site.
Back in 2009, recognising Harlech’s value as a tourist destination, Cadw (the Welsh Government’s Historic Environment Service) wanted to overhaul the visitor experience by developing and improving the surrounding facilities to provide a world class heritage attraction. With funding from the Heritage Tourism and Convergence Funding Project (itself jointly financed by the Welsh Government and European Union Convergence Funds) Cadw appointed RL Davies & Son Ltd to carry out the works.
The project consisted of refurbishing the existing Harlech Castle Hotel (a former 3-storey Victorian hotel) and converting it to accommodate 5 luxury apartments, a new visitor area, a new retail shop and offices. There was also the new-build construction of an electrical substation, plant room, tea room and toilet block. Completing the project was a 47m new-build bridge, linking the visitor centre to the castle gatehouse.
The original Harlech Castle Hotel was built in 1876 by Samuel Holland, a local quarry owner and entrepreneur. Following the construction of the railway in 1867, the hotel helped establish the town of Harlech as a holiday resort. The building has been designed to incorporate the views of the Castle and Snowdonia National Park.
The Victorian building has been sensitively restored and adapted for modern use. The building has been re-roofed with recycled Welsh slate. The old cement-based mortar pointing has been replaced with lime mortar, allowing the building to breathe again. Internally, walls have been stripped of cement and thistle plaster and replaced with lime plaster. New interior works have been deliberately, yet sensitively, designed and constructed to provide contrast.
The new-build extension replaces a poor quality 1980s construction. Exposed laminate timber frame with expansive glass infill panels command spectacular views across the Snowdonia mountain range and provides a link with the landscape.
Whilst the hotel provided excellent access and control for daily visitors, the building had two upper floors that were surplus to Cadw’s requirements. Discussions with Visit Wales identified a shortage of 4-5 star accommodation in the area. These floors were converted into luxury self-catered accommodation with concession opportunities offered to local businesses.
During the pre-construction surveys, it was discovered that the hotel threshold level was less than one metre different from the level of the castle gatehouse. This provided an opportunity, through the building of the new extension, to create a level access between the two points.
Any bridge works between the visitor centre and the castle gatehouse would be subject to demonstrable design criteria, if approval from the Snowdonia National Park Authority (SNPA) and UNESCO were to be secured.
One of the big challenges for the project, both in terms of the nature of the works and the location, was working within the confines of a UNESCO World Heritage Site. The project required the delivery of a careful blend of conservation, refurbishment, re-build and new-build. For the bridge works, an 18 month period of modelling and consultation was required with the Design Commission for Wales, SNPA, UNESCO and the local community, in order to gain the necessary planning and design approval.
The solution for the bridge was to create a 47m ‘S’-shaped steel under-slung truss structure with minimal visual connections between the spans and the ground. The lightweight, slender structure sympathetically and sensitively connects the new visitor facilities with the ancient fabric of the 13th Century castle. For the first time in 600 years, visitors of all abilities are able to access the castle as originally intended.
Another challenge for the project team, discovered during the excavation for the foundations of the new-build extension, was unearthed human burials, including 13 bodies dating back to the 15th Century, as well as the remains of two buildings, medieval street frontage and associated features. At one time, the project employed six full-time archaeologists.
One of the significant drivers of this project is, within the confines of sensitively restoring a Victorian hotel, a commitment to sustainability in the construction and running of the building, along with a number of innovative, low-impact building techniques and features:
The solid stone walls of the old building are not waterproof – when it rains some water is absorbed by the stone and mortar. The outside walls have been repointed using a breathable lime mortar and the inside walls are covered with a breathable lime plaster and special paint. The materials allow water to escape and help walls dry out if they get wet.
The building has been well insulated to reduce heat loss to the outside. The large glass windows overlooking the castle are also double-glazed.
Green roof and storm water attenuation tank
Plants on the roof of the new build extension absorb C02 and release Oxygen. The green roof also provides some extra insulation keeping the building warm in winter and cool in the summer. Plant varieties for the green roof are specially locally selected in order to encourage indigenous insect species. The green roof has the additional function of collecting rainwater into a large attenuation tank and subsequently into a stream that runs under the carpark. In the event of a storm, the tank slows the flow of water into the stream and reduces the potential for flooding further downstream.
Bat roosting boxes and bird boxes
Bat roosting boxes have been fitted to the eaves of the building, which are heated and made of material specifically designed with the right humidity and climate to encourage bats. Bird boxes have also been installed to encourage smaller bird species to breed in and around the building. The project itself is on the boundary of a ‘site of special scientific interest (SSSI)’ so close links to the natural environment are important.
The building uses LED lighting combined with a unique scene control system – combining energy efficiency with a selection of aesthetically pleasing light arrays. The system is quicker, more accurate and more easily changeable to suit the environment that conventional manual switching.
Nearly 30m² of Photovoltaic panels generate electricity for the building, providing a long-term sustainable energy resource. The use of an Air Source Heat Pump instead of the existing propane tanked gas supply has improved efficiency and reduced costs. The combination of the ASHP with an underfloor heating system further reduces the building’s carbon footprint.
A large proportion of the manufacture of the lighting is carbon neutral, achieved by the the planting of trees locally to offset the carbon produced during the manufacturing process.
The project was awarded a ‘very good’ BREEAM rating at design stage, and is on course to achieve the same post-stage rating. The goal is to achieve ‘excellent’ for the operational energy use.
Delivery of the project has provided a significantly increased offer to visitors, has the potential to increase visitor numbers, provides facilities representative of a World Heritage Site and introduces new economic opportunities to local businesses through the provision of catering and holiday accommodation within the new facilities. Getting all the details of this project right, from planning, excavation, building and sensitively managing the new-build and restoration elements requires a contract that the project team can trust. The JCT Standard Building Contract With
Quantities provides a framework to capture the requirements of complex and detailed projects to ensure that all parties have confidence in delivering world-class projects.
Main Contractor: RL Davies & Son Ltd
Architect and CA: EPT Partnership
Civil and Structural Engineer: Mott MacDonald
M&E Consultant: Jacobs
BREEAM Consultant: Mott MacDonald
CDM Advisor: Opus International
Bridge Technical compliance officer: Mott MacDonald
Bridge Sub-Contractor and superstructure designer: SH Structures, David Dexter Associates
Bridge Foundation Designer: Opus International
PQS: Rigby Thorpe
Landscape Architect: Lingard Styles
All images: ©Crown copyright (2016) Cadw