Most walkers pay little heed to the paths they rely on, yet without maintenance a busy trail will soon degenerate into a spreading scar. Path work is both hard graft and highly skilled. So what does it take to build an upland trail? Dan Bailey joins a team on the hill to find out.

Walking is big business, not only boosting health and wellbeing for individuals, but bringing wider societal and economic gains too. Yet the essential infrastructure underpinning it is crumbling. The hills have never been more popular; and all that footfall has an impact on the ground. Thanks to the weight of numbers, and the increasingly wild swings of our weather, many of our upland footpaths are an eroded mess, and getting worse. It's not clear when most might ever receive upgrade or repair. Among both walkers and policymakers, path upkeep is a subject that barely seems to register on the radar. Yet this skilled and time consuming labour, from which we all benefit, does not come cheap. The two key questions are, who will do the work; and how will it be paid for?

"Many walkers seem to regard the paths they use as something that's always just been there and needs no thought or care," says Julian Digby of Cairngorm Wilderness Contracts, one of the UK's few firms specialised in designing, building and maintaining upland footpaths.

"But these things need attention. Without maintenance, a well-used path will quickly deteriorate. Once the damage sets in, we've seen whole sections, tens of metres, wash out in a single summer storm."

The impact on the ground here is all too obvious. I've come to An Teallach to see the progress of the path upgrade funded by It's Up to Us, a fundraising campaign run by Mountaineering Scotland and the Outdoor Access Trust for Scotland (OATS), and to watch the team from Cairngorm Wilderness Contracts at work - also joined today by Eva Kupska and Ewan Watson of OATS, and first-time volunteer path crew Heather McNab.

It's hoped that the crowdfunding model pioneered here may eventually serve as a blueprint for financing path upkeep more widely across Scotland.

The need for fresh thinking is obvious. Tourism body VisitScotland estimates the annual economic boost of walking tourism at a cool £1.6 billion. While that figure alone might be thought to make a compelling argument for funding path infrastructure, there is in fact a major shortfall following the post-Brexit withdrawal of millions of pounds of EU money, cash that has not been made up by either the UK or Scottish Governments in budget-challenged times. National Parks and big landowning conservation bodies receive support - after a fashion - but beyond park boundaries, no public investment is currently directed towards mountain path repair on the 83% of Scotland's upland area that is privately owned.

A recent Upland Paths Audit suggested that £30M is required in Scotland alone for building and restoring the 400km of the path network in the worst condition. And to keep on top of that, estimates suggest an annual sum of £400,000 for ongoing maintenance across the network. If money is not made available from the public purse, might individual, charitable and corporate donations cover the gap?

Time flies when you're digging holes. You get totally invested in each tiny bit of path you're working on

That's the intention of It's Up to Us, which has so far raised £241,000 of the £300,000 target for its first project on An Teallach. Most of this has come via charitable donations from big funds such as the Scottish Mountaineering Trust, with bungs from the hill-going public accounting for only around 15% of the total. We walkers will spend hundreds of pounds on a new waterproof jacket, yet never think to put a hand in our pocket to help fund the paths we take for granted. If the user-pays model is ever going to grow legs in Scotland, it's clear that a culture change in hillgoing circles will be required.

Work on An Teallach is in its early stages, but already the contrast between the unmaintained trail and the newly rebuilt stretches is eye-opening - one a mess of deep-cut and widely spread erosion, the other a beautiful winding trail of stone-pitched steps that's a joy to walk on. While the best-made paths blend with their surroundings, taking on an almost organic feel, the construction or upgrade of a route like this is in fact a painstaking and highly considered process. Good paths do not construct themselves.

"First we walk it, up and down, putting ourselves in the minds of the people who'll be using it," says Julian.

"We've got to ensure it's the route that walkers will be most inclined to follow. Does it take on the natural shape and contours of the hillside? Does it follow the desire line, or is it zigzagging too much and inviting a tendency for shortcuts where people take the line of least effort on the descent?"   

Today the Cairngorm Wilderness Contracts team - Julian, along with trusted employees Michael Perry and David Abbott - are giving an object lesson in the hard graft that goes into the paths we take for granted, prizing and rolling rocks from the surrounding slopes to form part of their carefully crafted stone pitching; shovelling trug-loads of finer gravel to use as aggregate; cutting out drainage ditches and constructing neat cross-drains, stone-lined channels that carry water across the path and away.

"With an aggregate surface that easily washes off, directing water flow is vital if you're going to build a path that'll last," explains Julian.

"This is a sponge of a hillside, so we're having to think a lot about drainage. We've always noticed that people hate walking in water, so once the bed of your path has become a runoff channel, that's when they'll gravitate to the sides and spread the erosion further."

In future years it'll be a special feeling to be able to come back and say 'we built that!'

The team try to stop that happening by channelling the flow away from the trail with catchment features to push it off at regular intervals. And by creating subtle natural barriers of rock and turf alongside the route, the hope is that walkers will be gently steered to stick to the rebuilt trail, rather than deviating onto the soft and easily damaged ground alongside.

"Believe it or not, we don't build paths primarily because we want to make it easier for people to walk," says Julian. "The first and main aim is actually to protect the fragile mountain habitat, by giving walkers a natural line that will keep them off the vulnerable peat and vegetation." 

The aesthetic ideal is to create a new trail that looks as if it has always been there. To that end material is sourced from the locality, using a rock type to match the area's geology, with each block oriented so that the already-weathered surfaces are on show to blend with the surrounding rocks. On An Teallach the team have managed to link sections of new stone-built steps with stretches of exposed sandstone bedrock, a natural pavement that makes for a varied and interesting route underfoot, as well as a long-lasting one.

"Running big stones off the hill one at a time takes ages," says Michael, who's busy digging out a pit of aggregate when I catch up with him.

"Lifting them in builder's bags from a local scree slope [agreed with Nature Scot, of course] and transporting them into position by helicopter sounds expensive, but it actually works out to be the cheaper option in terms of manpower. And it's much less wear and tear on us.

"I've been path building for nine years, and I love this job. But maybe it's a career for younger folk; it's definitely got a physical shelf life. You don't see many path builders in their fifties. And yes anyone physically able can work hard, but the big challenges that put folk off are the weather and the midges."

Come rain, wind, freeze or shine, the professionals are out in all weathers year-round, and only snow is a show-stopper. In summer, working in a claustrophobic midge net is often a sanity-preserving necessity.

With the raw material manhandled onto site, the trail takes shape in short stages. On steeper ground the standard method is stone pitching, the construction of steps built mortar-free out of heavier blocks, each carefully selected for size and shape to tessellate jigsaw-like with the rest, and aligned to offer a decent surface underfoot. Flights of steps are anchored with the biggest rocks at the bottom, and once the main stones are in place the gaps are packed with smaller material, hammered in tightly to prevent water ingress. It's a highly skilled process, requiring a practised eye every bit as much as brute strength.

On rough, remote hillsides, mechanised assistance is not generally an option, and the hand tools and techniques on show today have not much changed for centuries. But being an ancient profession makes path building no less skilled, with a learning curve measured in years out on the hill. In the absence of secure funding and a supported route into the profession, a big concern for Julian is how to pay to train the next generation of professional path builders, as well as the question of who will put on the necessary courses.

Learning the ropes today, volunteer Heather is busy wielding a lump hammer on hands and knees in the grime, and seems to be enjoying getting her hands (and face) dirty.

"There's so much to take in," she says.

"It's not a question of picking up random stones and laying them willy-nilly; you're thinking hard all the time about what piece to use where. This is really changing how I think about rocks.

"Time flies when you're digging holes. You get totally invested in each tiny bit of path you're working on, then it's great to look back and think 'that wasn't there two hours ago'. It's hard work, but it's a lot of fun and so satisfying. I love the outdoors and I don't mind getting mud on my face - it's path builder's makeup."

A keen hillwalker, Heather signed up to volunteer with OATS in order to give something back.

"This is a great use of my spare time, and I feel like I'm actually making a difference," she says.

"I'd really like to help see this project to completion. And then in future years it'll be a special feeling to be able to come back and say 'we built that!'"

Beyond the initial £300,000 target of the It's Up to Us campaign, and the sections of new path that it supports, work to fully restore several remaining kilometres of worn-out trail on An Teallach will require a renewed fundraising effort. And this one hill is potentially just the start. With a great many upland paths across the country in dire need of repair, a finite number of volunteers and properly skilled professionals to do it, and a lean public funding environment that looks set to get no better, OATS and the campaign team have a mountain to climb. Perhaps we should all consider helping them with our time or money?

• You can donate on the campaign here