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Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

Discovery Center to Join Ancient Heritage Landscape

By Catherine A. Cardno, Ph.D.

The Sill, a landscape discovery center, business hub, youth hostel, and cafe, will be built in Northumberland National Park in England, near Hadrian's Wall.

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A 2,900 m2 building that will host a landscape discovery center, youth hostel, and cafe featuring local produce—among other amenities—will be built amidst the ice-age-formed landscape of the Northumberland National Park. Courtesy of Jane Darbyshire & David Kendall Ltd.

February 24, 2015—In the north of England stands Hadrian's Wall: a stone wall typically measuring 3 m thick and between 5 and 6 m high that extends 117 km from the Solway Coast on the country's western coastline, to Wallsend on its eastern side. When initially built almost 1,900 years ago, turrets located every 0.3 mi provided observation and signal posts, while small "fortlets" every 1 mi and larger forts every 2 mi provided accommodation and defensive posts for groups of soldiers. A great man-made valley-referred to as the Vallum-extended parallel to the wall on its southern side and measured between a few meters to a kilometer wide. With turf mounds running along either side of the Vallum, it effectively acted as an additional defensive measure and limited wall crossings to protected causeways and gates.

It might sound suspiciously similar to the great northern wall of George R.R. Martin's book series Game of Thrones , brought to life in the HBO series of the same name—and it is, points out Stuart Evans, head of corporate services at the Northumberland National Park Authority. Martin spoke in a Rolling Stone interview last year about how his imagination was sparked by a 1981 visit to Hadrian's Wall.

Built in the early second century A.D., the wall traversed a craggy landscape formed in the last ice age and protected the northernmost boundary of one edge of the Roman Empire. Much of the wall still stands, as do swaths of the great Vallum. As part of the frontier of the Roman Empire, Hadrian's Wall has been identified by the United Nation's Educational, Scientific, and Cultural Organization as a World Heritage Site. 

To encourage tourism, a new £14.2-million (U.S.$21.9-million) Landscape Discovery Center—which will include exhibition and education spaces, an attached youth hostel, a business center, a local park ranger base, and a cafe serving local produce—will be constructed within the ice age-formed landscape of Northumberland National Park. To be built at a small village location known as Once Brewed at Hadrian's Wall, the new two-story building received £7.8-million (U.S.$12-million) in Heritage Lottery Funds earlier this month, enabling construction to begin so that the new center can replace a smaller, aging hostel, small visitor's center, and ranger base. (Heritage Lottery Funds are those funds from the United Kingdom's National Lottery that are disbursed to help projects that protect and promote the country's cultural and historic heritage).

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The building is named The Sill after a nearby geologic formation known as the Great Whin Sill. The 117 km long Hadrian’s Wall—built by the Romans almost 1,900 years ago—traverses the top of the Sill. © David Taylor/Northumberland National Park

The 2,900 m 2 building will work with the natural contours of the site and be partially embedded in the landscape to minimize its impact on the scenery. Portions of the structure will extend from the ground's surface to offer panoramic views of the area's natural beauty and Hadrian's Wall itself. Locally sourced materials will be used to reinforce the visual link between the new building and its surroundings.

The idea behind the design of the building is "to really excite people, engage people in the great outdoors," says Alison Thornton-Sykes , a principal architect of the Newcastle upon Tyne-based firm Jane Darbyshire & David Kendall (JDDK) Ltd. 

The building is intended to be "a gateway to the wider national park and national landscapes for discovery," Thornton-Sykes says. "One of the most prominent features [of the area] is the Great Whin Sill geological outcrop, which is a fantastic escarpment, very dramatic; part of Hadrian's Wall sits on top of it," says Thornton-Sykes. This proximity-only a five-minute walk-inspired the building's name, The Sill.

Three main structural solutions have been chosen for the building, according to Thornton-Sykes. These respond to the three sections of the building: a softly curving ramp on the building's southern edge that will provide access from ground level to the rooftop garden; the angular, jutting northern edge of the building that will house the second-story, glazed-wall cafe and rooftop park; and the partially sunken end of the building that will house the youth hostel. 

"Due to the variation in building materials, the separate areas have been treated as independent structures with movement joints between each part of the superstructure," noted Mark Turner, CEng, the project director in the Newcastle upon Tyne office of the international engineering firm Patrick Parson, which is conducting the structural and civil engineering work for the project. Turner wrote in response to questions posed by Civil Engineering online. 

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Gabions filled with medium-sized Whin Sill stones—a hard, local stone—will be used to create a stepped appearance on the northern side of the building, reminiscent of rock outcroppings. Courtesy of Jane Darbyshire & David Kendall Ltd.

A cast-in-place flat-slab concrete framing system with retaining walls will be used for the southern end of the building. "To the south we've got the curved, sinuous wall formation, so we're using a concrete frame in that area," Thornton-Sykes says. The discovery center's centrally located 500 m 2 of exhibition spaces also necessitated wide, free-span bays that the cast-in-place concrete frame could provide. Concrete was the "best solution to achieve the curves, the spans, and the retaining-wall structures," Thornton-Sykes notes. 

To maintain the sleek internal appearance of the open areas, the flat-slab thickness varies to minimize the number of required downstand beams, according to Turner. In this portion of the structure, "waterproof concrete has been specified in order to negate the requirement for waterproof membranes on the accessible, planted roof and the retaining walls," Turner noted.

The angular northern side of the building, which features a large glazed wall, will be built with steel. "It was more viable to work with a steel frame, where we don't have the retaining [wall and] the curve issues," Thornton-Sykes notes.

The youth hostel portion of the building "is more domestic in scale," Thornton-Sykes points out, because it will largely comprise bedrooms and bathrooms. As such, the structure has been designed with more typical load-bearing masonry walls on strip foundations with timber floors and a concrete roof slab, according to Turner.

The building will be supported by a combination of concrete pad and strip foundations bearing on glacial till at a depth of between 1.0 and 1.5 m, according to Turner. This provides an allowable bearing capacity of 100 to 150 kN/m 2 , he noted.

Regionally sourced sandstone will be used to create the appearance of dry stone walls on the site. "We wanted the southern part of the building to respond to [the local sandstone] and to use the sandstone in the dry stone walls, so that the building really feels like its an extension of the boundary wall that you see in the landscape, which melts with the landscape to the north," Thornton-Sykes says. 

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Regionally sourced sandstone will be used to create the appearance of dry stone walls along the southern edge of the building to visually tie the structure to the area’s traditional wall-building techniques. Courtesy of Jane Darbyshire & David Kendall Ltd.

This will be accomplished by tying the sandstones back into the concrete block infill panels, Turner explained. "Partially dressed stone will allow a height of 3 meters to be constructed whilst giving the appearance of a dry stone wall," he said.

Gabions that will be filled with medium-sized Whin Sill stones will be used to create a stepped appearance on the northern side of the building. This side of the building "will feel very much like an outcrop in the landscape," Thornton-Sykes notes.

Locally sourced Larch timber will also be used to provide such cladding elements as raked canopies and siding.

Local Whin Sill vegetation includes rare plants and grasses for which the area is renowned. Examples of this vegetation will be grown atop the roof and ramp area "to give people the opportunity to engage with the wider views, but also to explore the habitat with really close viewing, and study its growth over time," Thornton-Sykes says. "People who might not be able to fully access the trails and walks, …can fully access the roofs," she adds. The ramp and rooftop have been designed to be wheelchair accessible and offer multiple stopping points.

The building's engagement with the area's fauna is also fundamental to its practical design. "We're also trying to encourage some wildlife onto the building," Thornton-Sykes says. "For example, there are bats on the site at the moment, so we're actively creating little bat roosts and crevices in the stonework walling around the building to create habitats within the building. It's all about the detailing, really, and we're trying to create this biodiversity and encourage habitats-as long as they're not detrimental to the building."

The design team is aiming for a Building Research Establishment Environmental Assessment Methodology (BREEAM) rating of excellent, according to Thornton-Sykes. A biomass boiler that will burn locally sourced wood chips will be used to heat the building and its water, and rooftop solar panels will be included as a secondary system to heat water. A south-facing canopy will provide solar shading to the windows and will include photovoltaic panels that will generate electricity for the building.

"The heating and a lot of electricity generation will be from renewables, and that's been tied in with the orientation of the building, natural day light, and natural ventilation whenever possible to really make it as environmentally friendly as possible," says Thornton-Sykes. The goal was to create a contemporary building that was a product of its times, incorporating as many low-carbon elements and other sustainable materials and processes as possible, while at the same time incorporating traditional materials and crafts to marry the new with the traditional, according to Thornton-Sykes.

Still, the structure will not be a net-zero building. Preserving the sight lines and the beauty of the site was of paramount importance. "To achieve full zero, you would have to go down a wind turbine route," Thornton-Sykes explains. "Because of the sensitivities of the site, that wasn't felt to be appropriate," she says. 

The building was designed with significant input from members of the local community, covering everything from materials to design options. "We really developed and designed with the wider community, so that's been a really interesting process, really rewarding," Thornton-Sykes says. "We generated a lot of really good ideas, which have gone into the design."

On-site work will begin in the late spring or early summer with the construction of a barn habitat for the bats to roost in during construction. The demolition of the site's existing buildings will occur shortly thereafter, timed to take place before the bats hibernate for the winter. 

Construction of the new discovery center and youth hostel is anticipated to be complete for a June 2017 opening, although an additional £2.2million (U.S.$3.4 million) still needs to be raised for the project. Once open, the building is expected to see 100,000 visitors annually. 

 

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