“We did a tunnelled sewer diversion that was 'back to traditional' [construction]. There's a 600 mm sewer that runs through the middle of the new-build.” He says Yorkshire Water doesn't appreciate contractors putting new-builds on top of sewers, since it needs full access to its utilities.
This meant the sewer needed to be diverted to the perimeter of the front of the new extension where it forms a dogleg about 100 m long, with depths ranging from 3 m to 5 m.
“Because of the nature of the services that are around the perimeter – such as fibre optics and HV cables – we couldn't do a traditional cut and fill from the top, so we had to go 'through', he says. “We had a 1,200 sq mm excavation with timber sleepers and it was traditionally excavated and taken forward.
A tunnelled sewer diversion went ‘back to traditional’ construction
A tunnelled sewer diversion went 'back to traditional' construction
“We put a steel former in place and then shunted the pipework along them. You're restricted; all you've got is the shaft you've dug for a manhole and you're digging from one manhole to the next,” Mr Sutcliffe adds, joking that it was like the tunnel in the film Escape to Victory .
“We were bringing back the material in trolleys with a little railway track going up the excavation. It's all manual work [with the material going] into a little basket on the railway.” These went back to the main shaft where workers could lift them out.
The new-build sits on concrete pad foundations, measuring around 3 sq m, that run in line with the existing structure and bear directly onto the underlying weathered mudstone and then hard rock stratum.
The only occasion that piling was used was for the wall of the original basement excavation. But Mr Sutcliffe says the need for these was negated as the footprint and hence the design of the building evolved.
Designed for inclusion
“There are scooter charging points where people might need to transfer to a wheelchair,” Mr Sutcliffe says. “They come in the building, swipe [for access] and it's all about planning for how staff can get from A to B.”
He says features such as the strategic positioning of automatic doors have been carefully thought through. “There's no reason why disabled people can't open doors manually, but in this scheme the client wants [some] doors to be automatic. I think it's going beyond [the normal consideration for a building of this kind], you don't normally have a route that disabled people can follow and every single door would be automatic.”
He explains that regulations dictate the force required to open a door so that less-able people have easier access. “But here the client's chosen to go down the [route] where it wants automatic doors [or hold-open doors] everywhere,” he says.
Careful consideration has gone into the fire escape routes for less-able workers. “There's a disabled refuge in the centre of the building with an alarm that buzzes down the stairs so that people know where stranded disabled people are,” Mr Sutcliffe says. “We've got evacuation lifts [here] that you don't have on every job.”
Both buildings feature these lifts that only members of the fire brigade can operate. One difference from a standard lift is a 25 mm ramp that rises to the door. This prevents water from fire hoses cascading down the shaft and interfering with the electrical systems, rendering the lift inoperable.
“There are [also] disabled refuges on the outermost escape stairs at the ends of the building where a disabled person, if they were blocked from getting to the lift lobby, would go to an alarm and the fire brigade can retrieve them from there,” he adds.
There are more everyday accommodations, too. A partially sighted council staff member has advised on differential finishes, with varying light reflectance values dictating colour schemes that will be used throughout the project. This extends to those used in the toilets.
These differentials are planned at points of changing geometry such as the intersection of a floor becoming a wall. Both elements should be at least 30 points apart on the 0-100 LRV scale so that depth perception and spatial awareness can be more accurately gauged by a partially sighted person.
This also applies to, say, surfaces in an office kitchen being different from cupboard doors, those doors to the kitchen walls, and so on.
It's especially pertinent to projects where spaces become enlarged (walls are removed to create one large office). “With open plan offices, for instance, it's about being able to assess the volume of the space… to see where the floors finish, where the walls start and where the ceilings are,” Mr Sutcliffe says.
Some of it is easier to implement than it might at first seem. “The long thin parts of the building are glass curtain walling blinds that differentiate themselves anyway, as a certain percentage of windows creates that difference in reflectance. So you've got dark carpets, white walls and glass,” he adds.
“There are white ceilings, but they're differentiated by linear strip lights that change the feel of the ceiling. The end wall of the office will be painted blue to give a difference between the floor and the wall. Partially sighted people can then feel the depth of the room so that it doesn't feel like it's going on forever.
“I've never built an office – an open plan environment – with those sorts of considerations. Within a kitchen space where you're designing for partially sighted people I'd expect there to be that differentiation – but how many offices do you go into that are just white walls and white ceilings?”
The new-build also diverges from the old by featuring a steel frame as opposed to a concrete one. Internally, the three structural cores comprise two for lifts and one for stairs. These provide all the structural stability that the steel frame will require.
'It wants to fall over'
“It's a bit of a strange shape, it's trying to fall over onto the road,” Mr Sutcliffe says, a situation not helped by it cantilevering out by about 1.5 m over the pavement. “So they're doing all the hard work with holding the building up.”
The BREEAM Excellent building will now feature two gas-fired generators in the basement that Leeds City Council, as opposed to the landlord, has decided to install at a cost of about € 2m. These will feed back into the grid at peak times.
The project is notable for the care taken to accommodate the council's staff that have disabilities.
“The council is catering for its staff as much as for the public, so there's been a lot of work done in terms of how people will access the building and all the routes they will take through it,” Mr Sutcliffe says (see box ).
In a sense, the building has been something of a chrysalis for enlightened tenant / client Leeds City Council. Not least because the facility that's emerging is larger than the original, but also because New Merrion House will be set up for those with disabilities in ways that were barely considered when it was built in the early 70s.