Garden Myths: Number 8

Waterfalls and streams need a mains water supply.

The first time, on discussing creating a garden pond, the customer carefully explained where the mains water supply was “as I would need it” I was taken aback; but it has happened now a number of times. The logic I presume is that as there is water running it must be from the mains. To clear up any confusion the water is circulated by an electric pump. Using the water mains wouldn’t work for a number of reasons. Tap water contains chemicals such as chlorine and fluorine which are added that could harm the plants and fish, if you’re constantly adding more and more water from the mains where will the excess go to, what is your water bill going to be, what happens as the water pressure goes up and down, what’s going to happen to the water pressure in the house and a domestic water supply does have sufficient water pressure or flow rate for all but the smallest water feature.

Garden Myths: Number 3

Garden ponds need a filter.

Properly designed and planted a garden pond does not need a filter. Long ago when I was a child we had a garden pond, along with many other people of course, but no one had a filter on them. This was for a good reason; they didn’t exist for garden ponds. What changed things was when people in this country discovered the hobby of keeping Koi fish. These fish are large, colourful, expensive thugs that dig up any plants growing in the pond. This meant people wanted ponds with just the fish in them but the fish could not survive in these conditions so Koi keepers invented the pond filter. This allowed pond water to be artificially kept very clear so people quickly realised it was easier to fit one of these to the pond to get clear water without the fuss of making sure the pond was properly planted up.

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.

Walling Materials

Brick wall detail at Lartington Hall
Brick wall detail

Historically walls have tended to be built from the nearest suitable materials and this has to very individual regional building styles. Since the advent of modern mass transport this has begun to be broken down; except where local planning restrictions have protected it. That is not to say the local traditional building style has to be followed slavishly, if any is discernible in the first place, as often the use of a contrasting material can be very effective. Making a clear demarcation between the old and new; always fair better than a poor match.

Traditionally walls have been associated with bricks or stone pieces with a mortar between them to stabilise the structure. As a building technology this is a very old one; and was well established by the time the Romans combined this with the arch allowing them to create their major engineering feats. The individual units that create a wall tend to be small, partly from practical considerations and partly from aesthetic ones. The small individual units imparts great flexibility into any design for a wall, allowing the same wall to be both straight and curved at different points. Its appearance can also be uniform if the same material is used throughout or broken up if the sizes and/or colours of the materials are varied.

Walls though don’t have to be brick or stone; the material used for their construction is only limited by the designer’s imagination. Concrete, timber, recycled bottles and wire cages filled with cobbles have all been used to make walls. The choice of materials dramatically alters the effect wall will have within the garden, as will its detailing and height.

When choosing the material to build a wall the range of possibilities is vast, with hundreds of different bricks alone to consider. When deciding on a walling material a number of factors have to be taken into consideration:

What materials have already been used?

How much are you prepared to spend on the wall?

What is the danger of frost damage?

How solid does it need to be visually?

How high does it need to be?

What if anything does it have to support?

How important is it to the appearance of the garden?

What finished appearance is wanted?

What shape is it going to be?

What is the purpose of the wall?

While this list won’t make the selection for you; it will narrow down the search, help focus your mind and hopefully broaden your mind to less obvious possibilities.

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.

Utility areas

Most gardens end up with an area for the bits you would rather not show off; where pots, wheel barrows and the like need to be stored. These areas need to be kept clean and tidy, so the paving needs to be smooth and easy to clean. As this is the working part of the garden, cost is an issue and often the cheapest smooth flags will the best. Where the area is going to be heavily used; or a greenhouse or heavy shed are to be set on them the solid 50mm thick flags are a better bet. Alternatively a plain concrete pad can be laid. In any case, as with all paving, care should be taken to ensure the paving is laid onto a good base capable of supporting the weight of what ever is going to be placed on the flags. Consideration should also be given as to the drainage of the area with a good fall towards an area of the garden any water can safely soak away into.

Sometimes the line between the garden and the utility area can be blurred, particularly where fruit and vegetables are to be grown. Gravel paths look very good running between vegetable beds but the work in them invariably involves stepping between the path and the soil. This will always result in soil ending up on the path and you want to be able to easily clean this off if the path is to remain usable. Clearly this is going to be very difficult with a patterned flags and impossible with a gravel path. Here pragmatism should not be sacrificed for appearance. Grass paths do provide an alternative to paving stage-manage but you have to consider if their appearance outweighs the problems of cutting them and their becoming muddy. While grass paths through provide a softer organic appearance to say a vegetable garden they are not easy to clean, can be difficult and time consuming to mow and can quickly become muddy if used a lot in wet weather.