A common problem with wooden steps is that the tread compacts with use and water collects behind the riser. Trampling turns the surface to mud, which is carried away on boots or washed away by rain. The steps are abandoned as they become uncomfortable to use, and a path forms alongside.
This problem can be lessened by proper surfacing and drainage:
- The tread should be formed of free-draining material which will not be carried away on boots. Do not use clay or organic soil.
- Prevent ‘waterfall’ flows down the steps by constructing a cross-fall or camber to shed water off to the side. On steep slopes and impermeable ground, install a French drain down the side. Alternatively, lead the water off every five or so steps into a short open drain leading away from the steps.
- The sides of the tread can be protected with suitable stone where available, bedded onto a solid foundation to prevent subsidence, and with the top set level with the top of the riser.
Alternatively, timber can be used, nailed to the risers and secured with stobs.
Treads should always slope from back to front to allow water to drain off. Do not sink the bottom of a riser below the top of the previous riser in an attempt to prevent the tread eroding, as this only worsens the effect illustrated above. To reduce the waterfall effect down the face of the steps, the tread should have a cross-fall or camber to shed water to the side. A camber will not be as durable as a cross- fall , but should be used on steps taking a direct line up a slope.
On steps where the tread mainly comprises ‘fill’ material, the tread can be built up in a similar way to a surfaced path. Local material from borrow pits, scree or stream beds should be suitable. Grade the material as shown, and put in a cross-fall or camber to direct the water away from the step.
Steps where the tread is partly comprised of fill can have a ‘toe’ or French drain of free draining material to take water from the tread.
Steps cut into steep slopes of clay need a surface dressing to prevent the treads becoming muddy and eroded. Crushed stone of about 20mm to dust, well trodden down, is suitable. This will need renewing periodically.
However carefully treads are constructed, maintenance will still be necessary. On some sites it may be decided, probably after much agonizing, to use concrete for the treads. This weathers to an unobtrusive colour, which on chalk or limestone may be not so different from the natural material, but will give a much more durable surface.
Drains
On moderate clay or peat slopes, an open ditch can be dug. Water must be able to flow freely into the ditch, with no possibility of it being diverted back onto the flight of steps. Make the gradient of the ditch as smooth as possible, and where available, line it with stones. On steep slopes or those likely to slump, a French drain with a perforated plastic pipe can be constructed, running parallel to the flight of steps. Run it into a ditch or soakaway, so the water does not merely collect at the bottom.
Revetted steps
Where steps take an oblique line up a slope it may be necessary to build simple revetments to protect the sides of the step. Revetments will be essential where steps have to climb an unstable slope.
Where space is very restricted, for example on steps down to beaches, more complex structures may be needed. Stobs are replaced by 100 x 100mm uprights, braced with steel studding. Oak should be used for durability, drilled on site with a battery-powered electric drill. This type of structure is difficult to specify in advance, and detailed design must be decided as work proceeds.
Revetted steps should only be built where no better line is available, as they require a lot of timber and can look very obtrusive. See also Chapter 11 – Erosion control and vegetation restoration for other types of revetments which can be built in association with steps.
Sunken steps
On gentle slopes of free-draining soils extra long risers can be used, and the ends buried in the spoil dug from the tread. This discourages walkers from going around the side, and looks attractive as the stobs are hidden and the steps appear moulded into the hillside. Any turf cut from the line of the steps can be used to protect the shoulder of the slope. This is not recommended on steep impervious slopes, or where run-off is high, as the unconsolidated material will be simply washed away as the line of the steps acts as a watercourse.
Non-slip treatments
Log steps can get very slippery, especially in woodlands where humid conditions favour algal growth. Although the bark may seem to improve the grip, it should always be removed before the step is built, as it can itself become slippery and speeds the decay of the timber. Creosoting helps to reduce algal growth, and can be repeated at intervals as necessary.
The simplest method of improving the grip is to roughen the top of the step using a billhook. Alternatively, a recess can be cut in the top of the log using an axe or chainsaw. Do this after the step has been fitted, but before it is backfilled or surfaced.
The method shown below has successfully withstood several years’ heavy use at the Birks of Aberfeldy, Tayside. It is not too obtrusive, as the wire soon loses its silvery appearance.
