Boardwalks

These include sleeper walkways, duckboards, and fixed boardwalks with handrails. The first two types may be movable. All boardwalks are expensive and time consuming to build, and need some degree of maintenance. Because of this, they should not necessarily be the first solution tried at any particular site. Consider the following points.

1. A boardwalk should not be sited where it will either be undercut or buried as sand levels change. Slight movements of up to 150mm (6″) loss or gain can be coped with by using a design which can be lowered or raised. However, this requires frequent supervision as it may need moving several times a year. Boardwalks are not usually suitable for going up and over dunes, nor along the back, where levels can change rapidly. Those along the top of fixed dunes, such as at Holkham, Norfolk, can work extremely well. Other successful boardwalks, through extensive areas of fixed dunes, include those at Ynyslas, Dyfed and Braunton Burrows, Devon.
2. All boardwalks need some degree of maintenance, according to the level and type of use, the incidence of vandalism, the degree of sand movement, and the initial design specification and quality of construction. Badly maintained boardwalks which have tilted, or have missing or broken decking, loose wires and so on are not only dangerous, but will not be effective, as people will avoid using them. They also create an eyesore and a large amount of debris which will need clearing up. The time, labour and cost of maintenance must be taken into account at the outset.
3. The boardwalk must be designed with the use in mind. A route that is used by elderly people or those with pushchairs will need closely spaced or butted decking planks, and gentle slopes, preferably without steps. A handrail may be of assistance. Boardwalks for school parties and field study groups can be more adventurous to use, but need platforms and other points where groups can gather for discussion and study. The examples following give more details on design and width for different uses.

Sleeper and log walkways

Old railway sleepers are still available, at a price of around £5 for first quality sleepers, and £3.75 for second quality (1986 prices). They are thoroughly pressure treated and make a durable surface. Roberts and Venner (undated, p8) estimate a lifetim8 of ten years for sleepers placed on sloping ground well above the water table. Sleepers are normally 250mm (10″) wide, 125mm (5″) thick, and from 2.6-3m (8’6″-10′) long. The usual sleeper walkway design is shown below.

Sleepers should normally be used cut in half and laid at right angles to the line of the path as shown. They can also be nailed on top of sleepers which are laid along the line of the path at each side, for extra support and rigidity and for longer life in damp ground. This method uses more materials and is normally not necessary in dry conditions. Where only a narrow path is needed, the sleepers can be laid two or three abreast, in line with the path, and anchored with 600mm (2′) pickets or half-round posts hammered into the ground and nailed to the sleepers.

Whichever method is used, it is important to strain plain wire across the tops of the sleepers before stapling to help bring the timbers tightly together and to secure the sleepers against vandals. Where the sleepers run at right angles to the line of the path (the normal design), you can fix the wires most easily and securely by hammering in posts at each end of the section of path to be strained. Strain the wires between the posts and staple. Then staple them to the individual sleepers without driving these staples fully home. Where this method is impractical due to terrain or path design, just hand tension the wires as you lay each sleeper and staple them home.

On the Suffolk Heritage Coast, the sleeper walkway shown below is employed where lightly used footpaths cross marshy ground:

The wires are secured by stapling around one peg, which is driven in, and then fixing the free end of the wire to a second peg before driving this in to tighten the wire.

Half-round logs may be cheaper than sleepers and may be readily available as thinnings from nearby forestry work. Softwood should be pressure treated or at least peeled and creosoted. The logs should be buried flat-side up and wired together the same as sleepers. A log walkway at Holywell, North Cornwall, uses half round 2m (6-,”) x 125mm (5″) timbers set in the sand about 40mm (1.5″) apart, with two wires (3.15mm) stapled to each log, 300mm (12″) from the ends. The walkway can be lifted and re-laid as necessary, as sand levels change. The lack of runners underneath allows the walkway to follow contours and curves along the route, so that only minor adjustment and levelling of the sand is needed. Where necessary, steps are made as shown.

Sleeper and log walkways can be angled around corners by cutting wedge-shaped timbers as shown.

In damp ground, sleeper and log walkways tend to rot out quite quickly and also to swell and pop out of alignment. Sleepers can be laid on top of runners as mentioned above, but logs, which are of varying thickness, cannot readily be secured except by burying them in the ground.

Duckboards

Duckboards are slatted wooden walkways made of relatively light, portable sections which can be detached as necessary for adjustment. They are mainly designed for boggy ground but are useful also on soft sand, especially foredune ridges, where they can easily be shifted as the sand surface changes. The seawardmost sections usually should be removed and stored over the winter out of the reach of the high storm tides.

In places where vandalism is a problem, two or more wires should be stapled along the length of the walkway, to discourage removal of sections. Sections can also be wired to buried timber anchors, as shown, so that wire cutters are needed to free them. When the section needs lifting, the wires can be cut and joined so that the anchor can be re-used.

Design and dimensions vary, but it is important in all cases to space the slats close enough so that people with fairly narrow-heeled shoes find them comfortable to walk on. A 25mm (1″) gap is about the maximum. Even so, people may prefer to walk beside rather than on the duckboards, especially if they are pushing prams, and fencing may be necessary to discourage this.

One design, used at Braunton Burrows National Nature Reserve, Devon, is shown below. Each section takes 45 minutes to an hour to build.

The 3m (10′) sections are made on a template with a 50mm (2″) offset to one side so that the sections, when laid alternately, slot together and hold each other in place. Slats with knots may soon break but are easily replaced as necessary. The overall life of the duckboards is five to ten years (Roberts and Venner, undated, p9).

On slopes the sections can be cut as shown below, so that their ends continue to interlock neatly. Staking at the joints is necessary on slopes to hold them steady.

A slightly different design is used at Holkham NNR, Norfolk. Only three runners are used per section. These are of pressure treated pine, 50 x 100mm x 2.7m (2″ x 4″ x 9′) while slats are 25 x 125mm x 1.2m (1″ x 5″ x 4′) untreated pine. Slats are nailed up to each end of the runners, and sections are bolted together with coach bolts and anchor plates instead of interlocking as in the Braunton Burrows design.

At Braunton Burrows, a narrower duckboard design is used on a path over mobile sand which is relatively lightly used. Each section slots into the next one as shown by the diagram. Sections take less than half an hour to construct, but because there are only two runners the slats must be free of large knots to prevent breakage.

All timber walkways, particularly duckboards, require regular maintenance as the sand builds up or blows out from around them where they transect the foredunes and abut on the beach. Several methods have been tried to reduce the frequency with which they have to be adjusted:

1. Where sand tends to blow out from under the walkway, you can lay brushwood across the path beneath it, extending beyond it to either side, to help trap sand. Stake the walkway sections firmly to reduce tipping if sand drifts away. Sideboards have been used at Ynyslas NNR, Dyfed, nailed along the lower edges of the runners, but these may actually increase scouring because they are hard and clean edged.
2. Where the sand is trapped by the slats, so that the surface tends to build up beneath the walkway, you can occasionally lift the affected sections a few inches and dig out hollows 150-200mm (6-8″) deep below them to act as sumps to contain blown sand. Leave the ends of the sections resting on packed sand. This approach has been used at Holkham NNR, Norfolk. At Braunton Burrows NNR, Devon, by contrast, the aim has been to trap as much sand as possible. Here the duckboards have simply been lifted and repositioned as sand accumulates. Lifting and repositioning may be required several times a season for the first few years, but should be needed much less often as adjacent dune-stabilisation efforts such as fencing and planting begin to take effect.

Murlough track

This is a timber trackway, first designed and used at Murlough NNR, Co Down, with similar designs now used at other sand dune sites. The pressure treated timbers are joined by 4.00mm mild steel wire, spaced with 25mm (1″) pieces of alkathene water pipe. The track is built in 3.6m (12′) sections, so it can be lifted and relaid if necessary. The timbers can be of any size to suit the intended use. At Murlough the timbers are 1.8m (6′) x 100mm (4″) x 75mm (3″), to take upwards of 250,000 people per year, as well as estate and emergency vehicles. Over a mile length has been in use for 15 years, with minimal maintenance.

At Formby, Merseyside, a ‘rolling walkway’ of similar design uses plastic-covered steel cable, threaded through 900mm (3′) x 75mm (3″) x 50mm (2″) timbers, spaced 25mm (1″) apart. The walkway is made in 6m roll lengths, the ends being finished as shown. A disadvantage, along with other movable walkways. is that sections can be removed by vandals. The weight of these rolls does act as a deterrent.

Boardwalks

Boardwalks built with a permanent, rigid construction can withstand heavy use and provide a comfortable surface to walk on. They are raised above ground level to protect dune. marsh and other easily disturbed surfaces and to reduce the effects of drifting sand. Boardwalks may cost no more than sleeper walkways in terms of materials but they are relatively laborious and painstaking to assemble.

Boardwalks need little maintenance but you should check them each season and tighten bolts, replace occasional slats and treat the timbers as necessary. Very occasionally you may have to dismantle a section and raise or lower it according to sand movements.

The design shown below is in use at Ynyslas National Nature Reserve, Dyfed, where it runs through fixed dunes for about 470m (560yds) from a caravan site to the beach. The timber is tanalised softwood.

Both the design and route of the boardwalk have been very successful, with few problems over many years of use. Sections have been replaced, as time and wear have caused deterioration of the timbers. One design weakness which has emerged is that the posts have tended to rot at the point where they are cut to take the handrail. Rotting could be reduced by screwing the handrails direct to the posts, without cutting a rebate in the post, and by weathering the top of the post to a slope so that water runs off quickly.

On the Suffolk Heritage Coast, a simple design is used to take footpaths across marshy areas where the boardwalks may occasionally be covered by tides.

Elm has proved to be durable in these conditions and is used throughout. The chicken wire stapled to the tops of the slats provides a better footing than the boards alone.

Ramps and steps

Ramps

Raised boardwalks should have ramps rather than steps at their ends to make them easier to use by elderly and disabled people and those pushing prams. A simple design of ramp is shown below:

Where possible, ramps should have a slope not greater than 1:12.

Steps

Ramps are not always feasible or necessary, eg where a path ascends the steep slope of a dune face or cliff or where it leads to a view platform off the main route. In these situations steps may be easier to build and more secure.

Step designs must be adjusted to fit the situation. A few points are basic:

1. When possible, position steps a uniform distance apart. Otherwise people may find them difficult to use. Spacing should allow a comfortable descent, and there should be a 100-200mm (4-8″) rise between steps. The steps must be clearly visible when approached from the top end or people may just walk down the slope at the side.
2. Normally it is best to build an interlocking flight of steps, for strength and stability. Where the steps are subject to erosion (eg by tides, or soil slippage on soft cliffs) it is better to secure the steps independently to posts driven into the ground. This way damage to one step does not affect adjacent steps.
3. Where handrails are necessary for safety, make them an integral part of the step construction. The posts which support the steps should form the uprights for the handrails, and the handrails should be bolted to the insides of the posts. Where the steps traverse a cliff or ascend a gulley, it may be better to fix the rails directly into the cliff.

The simple step design below uses logs or sleepers with oak or tanalised softwood stakes.

A problem with sand-filled steps is that people tend to loosen and push the sand downhill. Also the steps are easily undermined by wind, unless the steps are built at a gradual slope. To reduce these problems, it is best to bed the logs in ballast 25-50mm, (1-2″ gravel or ‘crusher run’ stone) with about an inch of coarse sand on top. Drive the stakes in front of each riser and nail them to the risers before placing the fill. If the steps are in a cutting, earth over the ends of the logs. This helps secure the logs and prevents the fill washing out around the ends. Where this is difficult, use edging boards as shown.

The box steps shown below can either be filled with packed sand and topped with 12mm (0.5″) of gravel, or decked with timber slats.

The design below is used at Hayle, Cornwall, to provide access from a car park to the beach through sections of fixed dune. The steps link to sections of boardwalk.

Sand ladders

These originated in Holland, and have recently been used at Crantock, North Cornwall and Giltar Point, Dyfed. The design is similar to a large steel or rope ladder, which is anchored at the top of steep sandy slopes that are otherwise difficult to climb and liable to erode.

At Crantock, a ladder has been placed up a steep narrow dune between a car park and beach, to reduce the amount of sand pushed down as people climb up and down the slope. Such sand movement encroaches on the car park. The angle of slope is very steep, and although most people have no trouble climbing up the ladder, some find it easier to scramble down the bare slope rather than balance on the ladder when going downhill. However, even partial use has made a noticeable decrease in the amount of sand displaced. As sand movement leaves the ladder ‘proud’ of the surface, every few weeks it is necessary to swing it to one side or other, to keep it stable. Two or three times a season the anchoring timber at the top is dug out, and the whole ladder is moved 10 metres or so along the ridge. It is removed for safe storage in the winter.

The design uses a rope rather than a steel cable. The rungs are 75mm (3″) diameter tanalised timbers, 900mm (3′) long, with 25mm (1″) holes drilled as shown. The ropes are threaded through and knotted beneath each rung. The top is anchored by a 3m (10′) by 150mm (6″) timber, buried 600mm (2′) down.

At Giltar Point, Dyfed, a 30m length of sand ladder is used on a busy two-way stretch of the coast path, where it follows an eroded sandy gully. This ladder is of the original ‘Dutch’ design, using an 8mm steel cable threaded through the rungs, which are held in place by cable grips. On flatter sections of the path grips are used both above and below each rung. To keep the ladder in position, the cable is stapled to stakes driven in at 3m intervals. When the ladder becomes buried with sand, it is lifted and replaced along the same route.

In conclusion, sand ladders are useful in particular circumstances, where access is limited to a narrow corridor of unstable sand or sandy soil. They are less suitable for areas where there is general access over a wide area of dunes, as people are unlikely to use the ladder when there are other options. They also need fairly frequent checking and lifting to keep them effective.

View platforms

View platforms should be restricted to backdune areas and other sites where wind erosion around the installation is not too severe. The design should be adapted to the site and should be big enough to accommodate any large groups using the path. Routes to and from the platform must be clearly marked. It may be necessary to provide fencing or thorny barriers around the perimeter, especially to keep children from jumping off the platform and eroding the surrounding slopes.

The design below is from Saltfleetby-Theddlethorpe. The material is untreated softwood, which lasts well in the well-drained soil of the dune top. In wetter soil, joists should be tanalised and stakes should he tanalised or of oak. The stakes do not support the platform but simply anchor the flooring until plants can grow up around the edges.