Upland Pathwork

Construction Standards for Scotland

Contents

• Home
• Preface
• Section 1. Introduction to Upland Pathwork
• 1.1. Principles of Upland Pathwork
• 1.2. Environmental Impact
• 1.3. Path Assessment
• 1.4. Path Survey
• 1.5. Maintenance
• 1.6. Working Practice
• 1.7. Tools and Equipment
• 1.7a. Mechanised Equipment
• 1.8. Health and Safety
• Section 2. Upland Path Drainage
• 2.0. Introduction to Drainage Techniques
• 2.1. Ditching
• 2.2. Stone Lett
• 2.3. Stone Waterbar
• 2.4. Stone Cross-drain
• 2.5. Stone Culvert
• 2.6. Piped Culvert
• 2.7. Stone Ford
• Section 3. Upland Path Surfaces
• 3.0. Introduction to Surface Techniques
• 3.1. Aggregate Path
• 3.2. Geotextiles: Aggregate Path on Peat
• 3.3. Anchor Bars: Aggregate Path on Slopes
• 3.4. Stone Pitched Path
• Section 4. Upland Path Site Restoration
• 4.0. Introduction to Restoration Techniques
• 4.1. Materials and Use
• 4.2. Defining Path Alignment
• 4.3. Containing Path Use
• 4.4. Bank and Slope Stabilisation
• 4.5. Restoring Vegetation
• Glossary of Symbols
• Glossary of Terms
• Further Reference

3.4 Stone Pitched Path

Introduction

Stone pitching evolved from the smooth cobbled surface of ancient tracks and roads, into the traditional rougher cobbling of stalkers paths, suitable to the upland environment. Further adaptation developed the technique for recreational use, and to merge with the landscape. It has gone through many years of experimentation, and this is ongoing.

FUNCTION

Stone pitching provides a hard-wearing surface for steeper paths. It is commonly used where aggregate is impractical or has failed due to the gradient and erosive pressure of feet and water. The pitched surface can withstand these pressures, and, with sensitive construction, blends aesthetically with the surrounding landscape.

The best sites for pitched paths are where they merge naturally with the rocky appearance of the landscape. To enhance the aesthetic appearance they should avoid steep straight lines, and incorporate curves and variations in width, making use of natural features wherever possible.

A pitched path is not always easy to use. It does not absorb impact, and may be steep and rough. If it is too difficult users will cause further erosion by short-cutting or walking on landscaped edges. An alternative of softer grass will invariably be used if it is available. A comfortable walking surface is therefore essential for both ascent and descent, in all conditions. It is also important to ensure that site restoration and landscaping encourages walkers to stay on the path.

CONSTRUCTION

After choosing an alignment that fits the landscape, the main considerations are:

• provide a good surface for walkers, particularly descending; reduce the gradient with angled lines across the slope wherever possible
• produce a structure that is solid and immovable, and will withstand the most extreme pressures of use and water flow
• incorporate drainage features for a path surface that will not be under-mined, will be long-lasting and require the minimum amount of maintenance

Components

Stone pitching comprises various stone shapes and sizes, used in rough courses across the slope, to provide a series of irregular and random low steps and footholds, with a cobbled appearance.

The largest block stones are used as anchor stones at the bottom of pitched lengths, and at regular intervals throughout the length to support the stonework above. Large stones are also used at the path edge for structural stability.

Drainage features are incorporated at regular intervals. For path surface water these will be water bars, although cross drains can also be used. It is good practice to protect the path surface below the pitching with a drain close to the bottom. The top of the pitched length should be similarly protected. The path edges are contained, defined, and softened with turf, spoil and boulders (see Restoration Techniques).

Dimension guidelines

There are varying styles of pitching, attributed predominantly to the stone type available. The basic principles for construction remain the same.

• the overall path gradient should be kept as constant as possible by incorporating curves on short steep sections, and adjusting the pitched depth and surface level
• the path surface should be below the surrounding vegetation to encourage walkers to stay on the path; this may be achieved by path edge turfing and landscaping
• anchor stones at the start of pitched lengths should have the tread flush with the lower path surface; if a step down is created, the surface below will erode, the step will become too high, and the anchor stones will be under-mined; this will cause the pitching above to fail
• path stone should be pitched with at least half the stone depth below the surface of the lower stone, and the longest side into the ground; the deeper the pitched depth the more solid the construction
• the resulting upstand, or riser should ideally be no more than 150mm; if it exceeds 200mm it can be difficult to use

• adjoining stones should form a rough course across the path with variable upstands to avoid a formal step appearance
• stone should be pitched vertically, with the tread surface more or less horizontal; downhill tread angles should not exceed 5°
• it is important that the overall surface is not a sloping ramp without good footholds

Materials

The local stone selected should be in its natural form, and preferably weathered (see Environmental Impact). The quantity of stone required for pitching is high - approximately 1 tonne for 2m², depending on the density and depth. If not enough is available in the vicinity of the path it may be necessary to import material to site by helicopter.

To avoid uniform steps a variety of irregular and random stone size should be selected. Stone varies considerably from thin slatey schists, and large rounded granite, to chunky sandstone blocks. Depending on what is available the following points should be noted:

• each stone should be deep enough to provide the pitched depth required - a general guide is no less than 300mm; anchor and edge stones will be deeper
• tread faces should provide a "grippy" surface; not so rough that protrusions may be tripped over, nor smooth and slippery

The best sources for stone are glacial surface deposits, scree slopes or rock falls on the surrounding open hill. Stream beds are another source but tend to provide rounded smooth stone which has to be used with skill.

Method of Construction

Step 1

Form a path tray

• excavate a path tray along the selected path alignment, to the required variable width
• the depth of the tray should allow for the depth of the stone available, and for a finished path level below the surrounding vegetation
• where the path line is severely eroded, to a variable width and depth, it may require realignment, infilling or narrowing, without any excavation; this can be achieved with careful use of spoil, turf and boulders

Step 2

Set the pitched stone

Depending on the number of workers and the length of the path, pitching may be split into sections. If these are pitched simultaneously pay close attention to the overall gradient. To ensure that the path climbs at a steady rate, and avoid joining either too low or high, the next set of anchor stones should be visible to judge the height gain required.

Always start at the bottom of a section and work uphill.

• the first line of stone will be large anchor stones set flush with the lower path surface; it is essential that they are dug in deep and are immovable; they may also form the lower side wall for a cross drain at the base of the pitched length
• progressing up the slope pitch the stone into the tray in rough courses across the slope, to achieve the required random footholds and risers
• use large, deep stone at the path edges to form a strong edge
• butt adjoining stones tightly together, on all side faces, maintaining good footholds
• wedge all gaps firmly, before subsequent courses are pitched, so that all path stones are solid and immovable
• overlap joins on adjoining courses for a sound structure
• pack remaining gaps with smaller stone and gravel; this is essential to prevent the ingress of water under the pitching, which may cause loosening and wash out, or break up with water freeze and expansion in winter
• incorporate waterbars or cross drains at intervals required, with the bar, or side wall, stones tied in with path stone to maintain footholds

Step 3

Edge finishing

• use turf, boulders and spoil from path tray excavation to landscape path edges, ensuring that edge stone side faces are covered, the line is defined, and the appearance "softened"
• where necessary the edge finishing should raise the path sides to contain path use, particularly to avoid short cutting at corners
• use excess turf and spoil to re-instate eroded or damaged ground (see introduction to restoration techniques)

TROUBLE-SHOOTING

Key points to watch:

• firmly pack all stonework - this is timeconsuming but if neglected or not done thoroughly it will result in water damage and stonework collapse
• make sure joins overlap for a solid, stable structure
• provide secure footing - a rough uncomfortable surface will not be used
• avoid regular courses of stone that create a formal step

• match the pitching gradient to the path alignment - avoid steep sections by re-aligning and incorporating curves.

VARIATIONS

Stone pitched paths throughout Scotland reflect regional variations, the main influence being the geology.

The type and size of stone results in styles such as:

• Granite - large rounded stone - pitching with treads bigger than the average foot size and larger rises
• Schist - thin slate like stone - pitching with small treads of several stones, but dug in deep
• Sandstone - smaller blocky stone - pitching using several stone courses to form a "grippy" foothold

The incorporation of grass-seed in the packing between stones is suitable on some sites. The vegetation softens the visual impactof the hard pitched path. It can also help to stabilise pitching that may be susceptible to loosening.

MAINTENANCE TASKS

Stone-pitching should require minimal maintenance, other than drainage features and edge work. The main tasks are:

• pack and re-set stonework where there is any movement or visible gaps
• turf the edges where trampling and erosion has occurred
• block any shortcuts that develop

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