Some practitioners use the term 'floating path' though very few paths actually float in the sense that timber or ships float. Most artificial paths on soft ground function by spreading the weight of the walker (and the path materials themselves) over a wide area so that the ground pressure exerted is reduced to such a low level that the underlying material can support it. The most successful of these in the last two decades has been the 'flagged path'.
The problem of deterioration of paths on soft terrain is one which man has been having and finding solutions to for millennia! Going back to 6000 BC prehistoric man built effective trackways in the Somerset Levels using several different constructions.
In 1984, West Yorkshire Metropolitan County Council Countryside team initiated a trial on the Pennine Way above Holmfirth using 1.2 metre slatted wooden paling with polypropylene fastenings - not very different, in principle, to those used by prehistoric man. The prehistoric version worked satisfactorily for their purposes and lasted for millennia. But the modern version sank 4" into the ooze before stabilising at that depth. Walking on a path they couldn't see in 4" of mud was not acceptable to modern walkers!
Later Calderdale Countryside Service studied the stone packhorse tracks of the South Pennines which had withstood constant use over soft ground for centuries and are part of the vernacular scene in those hills. In 1987 they laid a trial length of a modern near-equivalent on the Pennine Way at Walshaw Dean using old stone flags. This proved to be over-engineered but it did work!
In the next two summers further stretches were laid on the same moor with progressively simpler specifications. Adjustments were made to flag type and thickness, drainage arrangements, the amount of site preparation, handling systems, and re-vegetation techniques.
By 1992 large scale programmes on the Pennine Way were being undertaken using the experience gained in Calderdale and from later developmental sections in Northumberland. The system was fully written up by the (then) Pennine Way Co-ordination Project in a 1995 Technical Report entitled 'Flag Paths'.
The Peak Park have laid many kilometres of flag path. See the report below which includes information on how flag paths are laid as well as other surfacing and upland re-vegetation techniques.
- Reclaimed mill flags, preferably of Rossendale sandstone type which has a good colour.
- Lay them smooth side down and the 'rippled' side on top
- Preferred size 3 to 4.5" thick, 2' 6" to 3' 6" wide, any length from 2' to 4' 6"
- The ideal is 4" thick and approx 2' 6" x 3' 6", giving (say) 4.5 yards of path per tonne
- Do NOT use York stone, concrete, oil-stained flags, or flags outside the thicknesses given
Delivery to Site
- Helicopter them in from a roadhead base in special tip-able cage pallets, or on timber pallets
- Three-man teams are always needed as a minimum to handle the flags on site
- Overland delivery tends to do more damage to the moor than you had hoped to repair
Preparing the Path Line
- Take off any protruding tussock heads to get an almost level base. A bit of filling with local material is also useful in places
- Do NOT break up any existing vegetation at, or below, the surface
- On bare surfaces create a lowered bed for the flag so it will sit into the surface
- In slurried, excessively wet, or extra soft patches lay heather bundles, old palings, geo-tex mat or similar to a create a new semi-firm surface and provide more support for the flag
- Where there is any slope consider putting in side drains - but not too close to the path
Laying the Path
- Let the path line wander a little where practicable to get a natural 'feel' and break up long views of a straight path [so much for the Definitive Line! ed]
- Lay the flags butted end-to-end to give mutual support and level them
- Replant any vegetation removed earlier around the edges of the flag
- Start re-vegetation immediately - may need use of 'nurse crop' grasses and feeding initially
- Re-vegetation over three years after laying the path is vital if a first class outcome and a natural appearance is to be obtained.
How It Works
- A man's foot acting directly onto the ground exerts a pressure of around 4 lbs per sq. in., but a man's weight spread over the size of a flag measuring 12 sq. ft (1728 sq. in) represents a pressure of only 0.12 lbs per sq. in.
- The average flag of 3 ft x 4 ft x 4" weighs about 666 lbs. So, when laid, it alone exerts a ground pressure of 0.38 lbs per sq. in. Thus the flag plus man together exert a pressure on the ground of about 0.50 lbs per sq. in.
- So the ground pressure for a man walking on a flag is reduced to about 12.5 % of the figure for that same man walking directly on the ground itself. Even softer moors were found to be capable of supporting loads of 0.50 lb. per sq. in. without sinking or the flag moving.
In the early to mid 1990s when many such paths were laid costs were between £25 and £55 per metre laid (approx 3 feet wide) dependent on the site and local complications. Clearly inflation adjustments need adding to get today's cost. Also, old mill flags are harder to find as many mills are being converted rather than demolished.
Why Choose this Method
The flags are a re-used product, chemically neutral, with a good colour, and a slightly rippled surface to give some grip for boots. The same slabs can also be used on site for steps and mini-bridges. After three years quality re-vegetation work the landscape will be well on the way to recovery and in a further two years should be spreading into the edges and joins of the path to soften the appearance. The completed path then requires virtually nil maintenance (other than drain clearance). A permanent, sympathetic path for generations to come.
Who Uses It
The Peak Park Pennine Way Management project has built thousands of metres of flag paths and explains the background to the project and how restoration techniques were chosen.
Moors for the Future was a project working to restore the moorland in the Peak District National Park. It used a variety of techniques including laying flag paths.
Yorkshire Dales National Park has built several flag paths, including long stretches on the Pennine Way National Trail.
The Cleveland Way National Trail has used stone flag paths and stone pitching to surface sections of the route across peat moor and on the coastal sections.