Their property company, Capital & Centric, began 10 years ago at the height of the recession but defied the economic downturn to develop a roll-call of major projects - other schemes on their books include creating a Â£50m film studio dubbed the 'Hollywood of the North' at the art deco Littlewoods building in Liverpool, and the mixed-use, residential-led Kampus, a Â£250m venture in Manchester city centre.
Now the firm is crossing the Pennines for what its bosses hope will be the first of many assignments here.
"It's a cool city and we've always enjoyed the vibe of the place," says Tim. "We've had some nights out and had a wander round and thought this is the kind of city that would get the kind of thing we do. It went to the top of the list of the cities we want to work with."
Eye Witness Works is a classic Sheffield building with genuine history. Its red-brick facade - broken up by dozens of sash windows - extends along Milton Street near Devonshire Green, its tidy architecture hiding a higgledy-piggledy interior where kitchen knives, scissors and pocket knives were once made.
The former occupier, Taylor’s Eye Witness, was founded by John Taylor in the early 19th century, adopting a name said to have been prompted by the line "No eye hath seen such" from Shakespeare’s Henry IV, Part 1. The manufacturer has moved to a 32,000 sq ft base on the Parkway Industrial Estate, previously owned by Sheffield Council - as part of a deal, the authority took on ownership of the works, which survived two world wars and was constructed in phases between 1852 and 1875.
Capital & Centric won a council-led competition to develop the site on a 299-year lease; the firm's proposals will also encompass Ceylon Works, another building left empty by Taylor's next door, as well as the construction of a new extension at the back.
Ninety-nine homes are envisaged, including townhouses and one, two and three-bedroom flats, but the exact number could change. "It's always subject to what you find in the building by way of structures and walls that you weren't expecting, and beams you can't remove," says Adam, who has form in Sheffield - more than a decade ago, while working for Ask Developments, he helped to turn Leopold Square from a disused school to a popular hub of bars with a boutique hotel.
"He always talks about this," says Tim mischievously.
"I do, because it's one of the developments I'm most proud of," Adam says. "We absolutely kept the essence of what those buildings were."
When finished, Eye Witness will have three courtyards - a central space with a 'pocket garden' on either side - as well as a café on the corner of Thomas Street. This is not intended to be a big money-spinner, but will foster a sense of community among residents.
Inside one of the proposed courtyards sits an enormous, deactivated press, a hulking tribute to the knifemaking industry. "If we can, we'll keep that kind of stuff and sandblast it down," Adam says. "It's absolutely part of Sheffield's history. Plus, trying to move it out... it's probably 20 tons of iron."
Distinctive features like the curved bricks around the windows will also be retained. "Today you just wouldn't get that," Adam remarks. "The cost would be too much."
He and Tim are wearing matching black tops and jeans - they have a brotherly air, and clearly share the same enthusiasms, admitting that antique buildings fire their imaginations.
"Generation after generation has worked here," Tim says. "It's on the wealth that was created here that the rest of Sheffield has gone on to succeed. Here you can buy a piece of that, almost. We feel the burden, and the opportunity, of being custodians of the building. We want our kids to be proud as well, and that's a good test - will your kids walk past and think 'That's a bit embarrassing'."
Adam says: "When you look at this you can immediately see what the potential is. In a way it's harder to design something new. A lot of the best buildings around are often - not always - older."
The pair, who both have families and live in Manchester where their business is based, met at a conference in the city seven years ago. Tim, 38, was training to be a lawyer, but decided to go into property instead - he made rapid progress and launched his own company, Centric. Adam, 48, had also set up a firm, Capital, and for a year they helped each other out before teaming up fully in 2011.
"Really we're a product of the recession," says Tim. "We were disheartened by some of the things we saw by the banks ruling the roost, dictating which things should get developed. Often some of our projects are in areas of high unemployment, and deprivation - you think 'That's not right, for a bank to be in charge of that decision-making process'. They only care about profit. We've been able to do what we've done without bank debt. Now and again, when we do stop for breath, we're both surprised at how far we've come."
Capital & Centric spends Â£2m a week on regeneration projects, and has completed more than one million square feet of space.
But despite the profits at stake, Tim and Adam are unusually principled. Their flats at Crusader Mill, an old textile factory behind Manchester Piccadilly station, were made available exclusively to owner-occupiers last summer, confronting the problem of investors snapping up desirable homes at a premium. "If you want to live in Manchester you have this massive problem that you can't buy it," Tim says. "We ended up with a huge queue."
Adam points out that that six of their hometown schemes are around Piccadilly. "We started off with one, and that opened the door to another. The great thing about Sheffield is it's still got lots to do. That's exciting for us because once we start in a location, we've done multiple things thereafter. It's quite unusual, I think, to get cities where you've still got fairly large-scale development plots within the ring road. And that's what we're moving to. Less and less young people drive cars, so more want to live in the city centre and be within walking distance, or an easy bus ride to work and leisure."
The land around Eye Witness Works - not far from The Moor, Heart of the City II and the bottom of Ecclesall Road - is 'absolutely prime now', he added.
There are separate proposals to build a towering, 850-bed 'co-living' facility - aimed at students and members of the public - nearby to replace Stokes Tiles on Moore Street, and a 26-storey block of flats is planned on a car park opposite Grade II* listed Beehive Works, another cutlery factory next to Eye Witness which is still in use, divided into workspaces to let.
"It's been on its knees for a long time because the new retail quarter was always the big event," says Adam. "I think Sheffield has almost stagnated for quite a long time, waiting for that to happen."
Young professionals in their 20s and 30s, families and retired couples who want to relocate to city centres are their typical demographic for apartments. But they would be keen to bring the company's NowHaus concept - strikingly modern terraced homes on the peripheries of towns and cities - to Sheffield, too. "There's a huge gap in the market for contemporary living in a suburban location," Adam says.
A planning application for Eye Witness is to be submitted in September. It is hoped approval will be granted by the end of the year, with a view to starting construction in 2019. Residents are expected to move in by the end of 2020.
It will be interesting to see what Capital & Centric might deliver in Sheffield next, given its ambitions elsewhere. Twickenham Studios is to open an outpost at the Littlewoods site, which was once home to the football pools and will soon support 2,500 jobs from make-up artists to costume designers and sound engineers.
"The impact on the city region will be huge," predicts Adam. "A lot of Chicago and New York scenes are filmed in Liverpool."