How to build a sleeper retaining wall

Retaining walls are never cheap or easy but building one from timber railway sleepers is probably as cheap and easy as you are likely to find. As the sleepers are simply screwed together their construction is well within the abilities of most people without any specialist building experience.New sleeper retaining wall

Equipment:

 

  • Spade
  • Sledge hammer
  • Tape measure
  • Pick axe
  • Shovel
  • Drill driver
  • 190mm circular saw
  • 200mm landscaping screws
  • Sub-base
    X

    Subbase

    This is a layer of crushed stone used under paving to form, in effect, a stable foundation for it and is found between the bedding course and the subgrade. It is made of stone which has been crushed and sieved stone to end up with a mixture of sizes from  normally about 40 mm down to dust. The proportions of the different sizes should be such that the smaller stones bind the larger ones together to stop them moving and these are bound together by the smaller onesl. The source of the stone varies widely according to what is the cheapest local supply and includes limestone, dolomite, and waste concrete and waste tarmac. It goes by various names; dolly, dolomite, crusher run, type 1, MOT type 1, road plannings, 40mm down  and many others. Ministry of transport type 1 is a type of subbase produced to stringent standards which while making it perfectly suitable for garden use it is a degree of over engineering. There is also type 2 and when I asked a technician at a quarry the difference compared to type 1 he just said “very little”!

     Dolomite has the disadvantage that it becomes saturated with water when you attempt to compact it there is a tendency for it to turn to something resembling plasticine in texture, although it hardens on drying out and road planning tend to become greasy when wet. Only hard stone should be used as even the hardest sandstone, for example, will rapidly breakdown to sand in use. Once spread subbase should be compacted with either a vibrating roller or plate BUT do not attempt to compact more than a 150mm deep layer at any one time.

  • Spirit level
  • String line
  • Square
  • pencil

In Summary:

  1. Plan out your wall.
  2. Dig down to firm ground.
  3. Lay the first course of sleepers, levelling them with sub-base and leaving gaps for drainage.
  4. Install a drain behind the wall.
  5. Lay the next course, butting them together and staggering the joints.
  6. Screw the courses together.
  7. Repeat with subsequent courses until you reach the required height.
  1. Plan out you wall.

When deciding on the line of you wall think carefully about the space you need, always allowing for the thickness of the wall. For example if it’s along the edge of a path how wide does the path need to be? Not just to walk down but will you need to take wheelbarrows and lawnmowers? Also do you need to consider drainage, if all you are creating is a level area of soil on free draining land this is not going to be much of a problem but if on the other hand you are paving the area the water needs somewhere to go. Lastly what happens at the ends of the wall? If the end of the wall is near a fence or wall you are going to have to support that and you may need specialist advice.

  1. Dig down to firm ground.

Once you have marked out the line of the wall you need to excavate the excess soil, keeping the topsoil separate. Moving even small qualities of soil is hard heavy work and you are at the very least going to have to spread the work out. If there is much to move there are a large range of excavators available for hire and some will go through a standard doorway. (While excavators can save a great deal of work without care they can also do a great deal of damage!)

Once the area is cleared you can prepare the foundation for the sleepers. Make sure you are down to good solid ground and you can simply build up from that.

  1. Lay the first course of sleepers, levelling them with sub-base and leaving gaps for drainage.

First set up a string line along what will be the front edge of the bottom course of sleepers and lay sufficient subbase over the ground the sleepers are to be laid on to level them. Use no more subbase than is necessary, not thicker than 150mm, and lay the sleeper widest face down onto it. Bed the sleepers down onto the subbase with a sledge hammer to get them level. It is important to get the sleepers as level as possible as you will not be able to correct this later on. Make sure they are level not just along there length but also front to back or the wall will end up leaning either out or in.

  1. Install a drain behind the wall.

New sleeper retaining wall end viewThe new wall is going to block the natural drainage down the slope so level 50 mm wide gaps between the sleepers along the bottom course and put a length of perforated drainage pipe behind the sleepers and cover it with gravel to stop it blocking up with soil and roots. This should make sure any water behind the wall is collected up and can drain away.

  1. Lay the next course, butting them together and staggering the joints.

Once the first course and drainage are in place you can lay the second course on top of it, but starting with a short length to ensure the joints are staggered. To cut a sleeper measure off the length needed and make around the sleeper using a set square and pencil. Then simply cut the sleeper from both sides using a circular saw with a cutting depth just over half the sleeper’s thickness. The sleepers can then be laid butted up end to end and screwed into place. Screw the two courses together.

  1. Screw the courses together.

New sleeper retaining wall screw detailUse landscape screws at least 50 mm longer than the thickness of the sleepers with at least two to ever sleeper. These are driven in with a drill/driver.

 

  1. Repeat with subsequent courses until you reach the required height.

Keep adding courses as you did in parts 5 and 6 above until you reach the desired height making sure to stagger the joints between the sleepers.New sleeper retaining wall close up

 

This technique will work well for low walls around the garden, including raised beds, and with a little ingenuity you can also built steps in!New sleeper retaining wallside wall

Liz McNee, Mark McNee, Mark McNee liked this post

Bond, English

This is one of the commonest method of constructing a brick wall which is more than ½ a brick thick and consists of alternating courses of heads and stretchers.

English bond brickwork

English bond brickwork

The minor wall building materials

Metal

Though important in building is garden use is rather limited but can if used carefully can be very effective. The term metal encompasses a vast range of material, many used since ancient times, and the suitability of a particular one will depend on the individual use planned.

Reinforced concrete

This material combines concrete and steel to create a material with excellent compressive and tensile strength. This provides the potential to provide some very graceful and elegant structures but the complex nature of the material means is design and specification requires specialist expert knowledge.

Concrete reinforcing should not be confused with crack control in concrete, by weldmesh or polypropylene fibres, which serves a very different purpose.

Plastic

Traditional plastic has not been used a great deal in garden construction but the vast range of different forms of plastics means it has great potential. It has the advantage that it is very rot resistant, can be moulded (and some can be machined), pre-coloured and even some is made from recycled materials means it is beginning to be used for more than pond liners and roofing sheets.

Glass

Used for hundreds of years, recent developments in glass technology means this is a material with great future potential.

Peat blocks

Traditionally these have been used to make raised peat beds, but have they have fallen out of favour in recent years as a result of the environmental concerns around peat harvesting and use.

Peat block wall

Peat block wall

The main wall building materials

Brick

Reclaimed brick walling

Reclaimed brick walling

One of the oldest and most durable building materials; its variability, flexibility, durability and strength has made a ubiquitous walling material. Traditionally made from dried earth the centuries of use and development has lead to a very sophisticated produce now mass produced in millions each year in the UK alone.

The earliest bricks were probably made of mud and date back at least 5000 years, and probably considerably more. Modern bricks are still normally made from fired clay (a natural extension of sun-baked mud) but they now come in a vast range of colours and surface finishes. It must be remembered that most facing bricks, while very strong are damaged by frost if their exposed surfaces are saturated with water. The only real exception to this is engineering bricks which are not as absorbent as facing bricks, but are only available in plain red or blue.

 Concrete

The use of concrete dates back at least 2000 years; it was used extensively by the Romans and there are Roman writings on its mixing, placing and use. Though its use has waxed and waned with changing fashions is seems every new generation re-discovers it, finding original uses for it.

Years of use and study have meant that what may appear to be a very simple basic material has become a very complex subject. What is frequently not appreciated is concrete, while having excellent compressive strength1, has so little tensile strength2 that is it regarded by engineers as having none.

Stone

The stone mason is one of the oldest trades and stone walls have been found wherever stones can be sourced. The earliest were probably dry stone walls built from stones found laid on or near the surface of the soil.  The durability and effective ness of these can be seen from the miles of dry stone wall which snake over the North Yorkshire Dales, where the shallow topsoil means the stones could be sourced by gradually picking up stones laid about the fields. Once metal tools had been invented stone could be cut, worked and polished allowing the creation of the pyramids and temples of the ancient world.

Wall detail at Dornoch Cathedral

Wall detail at Dornoch Cathedral

Stone comes in a vast range of forms and this determines it suitability for building and what results can be achieved. As one of the main costs of stone is haulage, traditionally it was sourced close to where it was to be used so lending distinctive local styles to walls.

 

Timber

Though not as durable as stone or brick, its easy of working and availability has meant it has long been used as a building material. It has also has other advantages over brick and stone work: it is a lot lighter, possesses tensile strength2, can be readily coloured with stains and paints, and although it does weather it is unaffected by frost.

Timber pole walling

Timber pole walling

Wood is though a very variable materials depending mainly on the tree species it comes from, but also the environment the tree grew in and the part of the tree it is harvested from. When used in construction this can lead to concerns about its structural strength and for this purpose it is “stress graded” but in a garden context the size of the timbers chosen for aesthetic considerations means this is unlikely to be important.

Notes:

1)      Compressive strength is simply the ability of a material to resist being crushed.

2)      Tensile strength is simply the ability of a material to resist being pulled apart, something that brick, concrete and stone walls actually lack. Hence the need for arches or solid lintels over openings in walls.

Parts of a Wall

Garden walls are constructed from 5 distinct elements:

Parts of a wall

Parts of a wall

Subgrade

Foundation

Walling materials

Mortar

Coping

 

The first, the subgrade, is the ground the entire structure stands upon and so its stability and load bearing ability determines on whether the wall is going to remain standing. For these reasons the wall foundation should be onto undisturbed ground that has not been built up from material such as old construction rubble or compacted hard core. For the same reason sufficiently deep so that there is no risk of frost and therefore frost heave.

The foundation of the wall is normally concrete and acts to spread the weight of the wall. Historically wall foundations could vary from nothing at one extreme to quiet complex structures and this depends more on the ground conditions and the builder/architect than the date they were built. A roman building could have a concrete foundation not unlike a modern while a country cottage built in the last few hundred years may be built straight onto the topsoil.

The walling material is the bricks, stones, etc. which forms the walls.

The mortar is the sand based material generally used between the pieces of the walling material and it serves the function of keeping the pieces of walling apart. It does not hold the pieces together, so walls have no tensile strength, but instead keeps them apart; so stopping them wobbling and stabilising the structure. The sand itself is held together by incorporating lime or more normally now cement to prevent it being washed out of the joints.

The coping tops the wall and protects it from becoming saturated with rainwater.

Types of garden walls

Free standing

The simplest walls are free standing and these are normally used when boundaries are walled. In the UK garden walls above 2 metres high, unless they face the public highway when its 1 metre, require planning permission. That said this is only a basic guideline and local rules or covenants can often apply so before you start any work you should make a quick call to you local planning officer. In practice these heights are quiet sufficient and you would need a very good reason before the authorities will allow you to exceed them. When considering the height of the wall you have to remember that if the ground level is lower at one side of the wall than the other the measurement is taken from the lower side and the height includes all parts of the wall including pillars, copings or anything else attached to the wall.

These days most garden walls are either ½ or 1 brick thick; though older gardens will often have 1½ or 2 brick thick ones. The choice of wall thickness will in the first case be determined by what is needed to ensure the wall is stable but then a thicker construction may be chosen for aesthetics. Clearly the thicker the wall the more expensive it will be and all walls are expensive, so a good reason is needed to make a wall thicker then it has to be. An excellent guide to the wall thickness needed for a particular location in the UK can be seen on the Government’s Planning Portal.

 Heated walls

 The idea of using a garden wall to provide heating may seem strange and very wasteful to us now, but at one time this was state of the art gardening. The walls were built with fireplaces spaced along their length and the chimneys took the form of brick flues snaking up through the walls. The hot smoke and gases from the fires passed up the wall flues, heating the wall as they went. Many are still seen in old large estates around vegetable gardens where they heated lean-to greenhouses built against them. They are easily spotted by the chimney post along the top and are usually thick and generally two stories high.

Heated Garden Wall from The Book Of Garden Management by S. O. Beeton

Heated Garden Wall from The Book Of Garden Management by S. O. Beeton

 Retaining walls

This is the commonest reason for walls to be used in a garden. Where a garden requires a change in levels, either by design or necessity, a wall is the most efficient method of achieving this. The wall must be sufficiently strong to support the material it is holding back and in the majority of circumstances this is achieved by the weight of the wall.

In most cases in the garden the amount of material being supported by the wall will be relatively small and the potential danger from the wall failing will be small. In practice, the aesthetics of the wall design will mean it will be sufficiently strong, but if the wall is going to need to be higher expert advice should be sought. Because by their nature retaining walls cut across the natural drainage of the ground there is a danger of water building up behind retaining walls. This can weaken the soil around the wall foundation and therefore weaken the wall. To prevent this drainage must be provided behind retaining walls which empties out through small holes in the wall called weep holes.

 Ha-ha

 The 18th century saw the English “leap the garden fence” and develop the English landscape Garden style where countryside became the garden, all be it in a much stylised form. To achieve this, the garden boundary had to be hidden to allow the garden to visually run seamlessly into the surrounding fields. To achieve this; the wall is set into the ground below eye level. In practice this is a very expensive process, generally requiring large amounts of earth to be moved in addition to the cost of the wall.

Sketch of a Ha-ha

Ha-ha

Garden walls

A sketch of a garden gate leading into a further part of the garden.The wall is one of the oldest manmade structures, and its use in gardens is as old as gardens themselves. The word comes from the West Saxon weall which in itself comes from the Latin vallum meaning a rampart and in the garden walls are used as a natural development of earth ramparts. Initially walls in gardens were to divide the gardens private space from the rest of reality, but over the centuries their roll has evolved.

It must have quickly become apparent that walls change the immediate environment around them; providing shade, shelter, warm and support. A wall facing the south will create an area of warmth immediately in front of it both by reflecting the suns warmth and by absorbing this heat and then gradually releasing it after the sun has gone down.  An east facing wall will heat up early in the day and then release its heat when it is in shade in the afternoon, where as a west facing one will heat up later in the day preventing the rapid and damaging thawing of delicate spring blossoms. A north facing wall on the other hand will be cool and shady demanding plants suited to those conditions.

What is often over looked though is the effect walls have on the moisture in soil immediately beside them. The porous nature of brickwork will tend to draw moisture from the soil against it.  A greater effect though will be from the tendency to prevent rain being blown onto the leeward side of the wall; making the side sheltered from the prevailing wind drier. This effect will be further exasperated by any over hanging coping and more so by the eves of a roof.

In addition walls have a psychological effect; changing the way we perceive the space they enclose and its relationship with what is beyond them. Their presence can create a sense of privacy and security to those on both sides of the wall. Even a low wall creates a strong dividing line between the parts it separates; allowing the areas within the garden to be compartmentalised according to their form and/or function. Thereby creating uniformity: stopping different styles and uses clashing; in forcing a sense of order.

A further layer is added to this relationship by the openings placed in walls. Large ornate gates form an imposing status symbol, framing and thereby controlling the view of the area with in. Small openings control both the access to the interior space and what can be seen of it creating a different sense of drama. This can be further manipulated by the choice of how this opening is filled. A solid door will block the view out of the walled area while creating a sense of mystery: while one that you can see through will entice the viewer though into the space beyond.

Each wave of garden design style has found new uses for walls, as the demands we place on gardens change and new materials to construct them from become available. Thus the role of the garden wall continues to develop with each generation of gardeners.