6. paving and walls · flagstone paving this description may conjure up images of old stone paving,...

PAVING AND WALLS MODULE 6 PAGE 1

6. PAVING AND WALLS OVERVIEW In this module, we cover the following topics: What is hard landscaping? Flagstone paving Block paving Gravel surfaces Decking Walling

WHAT IS HARD LANDSCAPING? Hard landscaping is a term used to describe that part of a garden that involves hard materials like paving and walling, essentially anything made of wood, concrete, metal or stone. Being the designer of the garden it is important that you understand the nature of these materials, so that you can use them to their best advantage. Not only does this help you to choose the right material for the job but also assists you in keeping the budget under control. In this module we will look at the most common hard landscape features found in the garden, the way in which they are constructed and some techniques to cut costs. By the end of this module you will have a better understanding of construction techniques, which will enable you to better instruct a landscaper as to exactly what it is that you are expecting and to avoid costly mistakes. You should also be starting to build up a portfolio of materials and suppliers for your own information and to show clients. USING PAVING IN THE GARDEN There are many different types of paving on the market, but they all fall into one of two categories; they are either flagstone paving or block paving. The following section describes the fundamentals of each one and the way in which they can be used.


FLAGSTONE PAVING This description may conjure up images of old stone paving, the likes of which can still be seen on the street of some of the older English towns and villages. This is a fairly accurate description and in bygone days that was the only choice of flagstone. Although still widely used today, natural stone is an expensive commodity. Over the years market forces have encouraged the production of imitation flagstones made out of concrete or reconstituted stone. This has opened up the landscaping market tremendously, allowing people who previously would not have been able to afford it, to have elegant terraces designed to reflect a whole host of different styles. To effectively bring this vast range of paving to your client means sifting through those available and not necessarily picking out the best, but that which best suits your clients' needs. Cost can be an important factor in this decision. Some of the imitation flagstones are extremely well made and even an expert would have trouble distinguishing it from the real thing; however they have a price to match. It is always worth having 2 or 3 choices that reflect different price bands and letting your client make the final decision. All flagstones, whether they are natural stone or reproduction, are laid in the same manner. Although there are several different methods of doing this, each of which will greatly affect the price of installation. METHOD 1 (FOR LIGHT USE) This method is sometimes regarded as a temporary measure, or for areas of low use. 1. If the finished level of the paving is to be the same height as the

surrounding ground, you must excavate the area to a depth equal to the thickness of the flagstone being used and an additional 50mm for sharp sand.

2. The base of the excavation is then compacted and the flagstones are laid

onto a layer of sharp sand and firmed into place.


FIGURE 6.1: CROSS SECTION OF METHOD 1 This method is ideal for shed bases and compost areas etc, and represents a low cost solution for laying paving. This method will keep the budget down, but if it is used in areas of high tread it won't be long before the flagstones start to subside and become uneven. Sometimes you only need a temporary patio, and it might be worth considering this as an option. However, proceed with caution and if possible use other options. As the firmness of the base relies upon the underlying soil, this method is best used in area with solid subsoil such as chalk. METHOD 2 (FOR MEDIUM USE) This method has two slight variations. But essentially its improvement over the first method is that it provides a base of its own rather than relying on the strength of the underlying ground. It has a slightly higher cost attached to it as more excavation is needed. There are larger amounts of soil to dispose of and more materials are required: in the way of hardcore and cement. 1. Firstly as with the first method, if the finished level of the paving is to

be at ground level then an excavation must be dug to a depth equal to the thickness of the paving slab, plus 50mm to allow for the mortar or sand and a further 50 - 75 mm for the hardcore.

2. Once the base of the excavation has been compacted the hardcore is added to firm up any soft areas and give the base a consistent level of support.

3. The slabs are then laid on either a mixture of soft sand and cement or sharp sand and cement or a mixture of the two.

This second method is suitable for most domestic paving features, whether they are patios or pathways. The flagstones laid in this manor will tolerate a high degree of use such as the pathway to the front door. This will probably be the most common method for laying flagstones that you will be specifying.

Compacted subsoil

50mm Sand

Paving


FIGURE 6.2: CROSS SECTION OF METHOD 2 METHOD 3 This final method is used in areas, which are expected to take a lot of weight. In most cases this will be a driveway or parking bays. Because of the extra weight involved, the base must be much more supportive. To achieve this, the hardcore base is deeper, usually no less than 150mm; and the slabs are laid on practically a complete bed of concrete which is around 100m deep. The extra depth of the excavation will increase the cost of removing the soil and also the amount of hardcore needed to fill it. 1. The method of installation is much the same as for method number 2.

Firstly the area is excavated then compacted and filled with the hardcore to the appropriate depth.

2. The flagstones are then laid on a bed of concrete instead of sand and

cement.

FIGURE 6.3: CROSS SECTION OF METHOD 3

Compacted subsoil

Paving

Hardcore

Sand/cement

Paving

Concrete

Hardcore

Compacted subsoil


EXERCISE 6.1 1. What is the advantage and disadvantage of laying paving on just a bed

of sand? 2. Under what circumstances would you lay paving over concrete and

hardcore.

BLOCK PAVING Block paving has evolved from the cobbled sets, which used to line our streets. As with flagstone paving block paving is offered today in both natural stone and concrete and in addition clay pavers are also available. The rules for laying block paving are simpler than for flagstones, and can be generalised as follows: 1. An area of blocks must always have an edge restraint. This could be an

existing wall or a new kerb. 2. Blocks are always laid on a 50mm layer of sharp sand. 3. The depth of hard core is dependent upon the weight that the blocks are

expected to carry. As a general rule this would range from none at all for really light use; 75mm for everyday pedestrian use; and 150mm for light vehicles such as a family car.

FIGURE 6.4: CROSS-SECTION OF BLOCK PAVING CONSTRUCTION Blocks are offered in a variety of different shapes and can be laid in many different patterns. The choice of pattern however does not rest solely with which looks best.

Hardcore

Compacted subsoil

Blocks

Sand Kerb and haunch


EXERCISE 6.2 Take a look at the two sets of pattern below and see if you can spot the common features of each set. The answer follows the illustrations.

FIGURE 6. 5: SET 1

FIGURE 6.5: SET 2

If you study the two sets, you’ll notice that in Set 2 the lines of joints between the blocks run in long straight lines in either one or two directions.


But in Set 1 these lines run no further than a block and a half. The consequence of this feature is that in set 1 the blocks will be much stronger and be able to withstand a far greater weight than those in set 2 because the bond is much stronger. One classic example of an error, which can be made because of this phenomenon, is that of a drive laid using a stretcher bond (shown below) running in the same direction as that of the car tyres. As you might imagine, if the car always uses the same tracks as it would on a narrow driveway, it won't be long before ruts start to appear. Whereas if the pattern were turned through 90 degrees the bond would be much stronger.

Joint in line with tyre tracks Joints at 90 degrees to tyre tracks

FIGURE 6.6 CUTTING STONE Cutting flagstones and block paving is all very possible now with the use of hydraulic block cutters and diamond tipped cut-off saws. However this can be a time consuming exercise and can increase the cost of a job considerably. If the budget on a job is looking stretched, you could easily save some money here by having a random edge to your paving instead of a precisely cut arc, or fill in any odd shapes with gravel or planting. It is nice to see precisely cut stone, and it can sometimes go a long way to finishing a job off, but it will come at a price.


OTHER SURFACES IN THE GARDEN

GRAVEL SURFACES The main alternative to paving in the garden is gravel. This is often used for informal pathways, in Japanese gardens or as mulch around planting. The quick and easy way to use this material is to just rake the soil level and put the gravel straight down. Regardless of what you are intending, the gravel to be used for this method has two major drawbacks: 1. The gravel will inevitably get mixed up with the soil beneath. Either

through foot traffic or from pulling up weeds. 2. Perennial weeds will grow though the gravel and start to make the

surface look untidy. If the gravel surface is to be used as a pathway, you should put down a layer of hardcore first. This will separate the soil from the gravel as well as suppressing the growth of the perennial weeds. If weeds are a problem in the garden, a geotextile membrane should be laid under the hardcore. This is available in a few different forms, but essentially is a woven plastic fibre sheet that will allow water and air to penetrate it but stops weed from growing through it. The main advantage of using gravel as a surface instead of paving, apart from it being less expensive, is that you don’t have to worry so much about where any surface water will drain to as it tends to soak straight down into the ground. Retaining the edges of gravel areas is also a good idea to help keep it tidy, as it does tend to kick around. The edge restraint can be anything from timber to brick, depending upon you design.

FIGURE 6.7 CROSS-SECTION OF A GRAVEL PATHWAY

WITH A BRICK RETAINING EDGE

Geotextile membrane

Gravel

Hardcore

Brick edge set on concrete


DECKING Once the principles of building decking are understood, its uses and advantages and disadvantage over other surface become much clearer. So let’s start with a quick lesson on how to construct a deck, and then we will look at its pros and cons. BUILDING A DECK There are three main stages to this process: 1. Create a supporting structure for the substructure of the deck. 2. Build the substructure using rafters. 3. Add the decking planks. 1. Create a supporting structure for the substructure of the deck.

This may be as simple as using an existing hard surface like an old patio or concrete pad. If the deck is going to be a large one then the sheer weight of the timber will stop the deck from moving around. However if the deck is small or the proposed site has no existing structure to use as a base, then we need to build one. This is simply a matter of concreting sturdy wooden posts into the ground at strategic points.

2. Build the substructure using rafters

If the rafters are to be built directly on top of an existing structure like a concrete pad for instance then they are simply laid out in a suitable fashion to support the decking planks, and packed underneath to level out any minor height discrepancies. If the rafters are to be fixed to posts, they are set level and bolted through the post.

3. Add the decking planks. The planks are fixed using screws. Stainless steel ones are best, but are expensive, otherwise zinc plated ones should be used. Plain steel will soon rust and discolour the wood and should be avoided.


Stage 1 Stage 2

FIGURE 6.8: CONSTRUCTING DECKING

FIGURE 6.8: CONSTRUCTING DECKING - STAGE 3 ADVANTAGES OF USING A DECK 1. If a base exists, the deck is very clean to install.

2. If a deck is to be at ground level, the area must be excavated to accommodate the depth of the rafters and the decking boards, plus a little to ensure the rafters are not in contact with the soil. The real advantage over paving is if the deck is to be above ground. With paving, some sturdy retaining walls need to be built to support the paving and will see the cost jump quite dramatically. To change the level of decking however is just a matter of making the supporting legs longer.

3. If decking is screwed down, it is a very easy operation to lift sections for access to drains and other services. Paving on the other hand would require a more complex solution.

4. Small sections of deck can de used around water to create simple bridges and jetties with no need for foundations inside the pool.


DISADVANTAGES OF USING A DECK 1. The only real disadvantage is its limitations on its position. A deck can

become very slippery if placed in an area which gets little sun and poor airflow. This factor overrides all of the advantages and must be considered first, otherwise the surface will degrade very quickly and become a hazard rather than a haven.

Many people are concerned with wood cracking and warping, and this can be a problem with some of the lower grade timbers. However, some people will sell this as a feature of the product and something to be expected from a natural resource. We will leave you to make your own mind up about that one! The price of timber will vary greatly depending upon the quality; and you should be sure to specify which grade you are expecting to be used. 1. If you are looking for good quality and long life in a deck, go for

hardwood from well-managed sources. 2. Next in quality are the dense softwoods, which are seasoned and kiln

dried before they are finished, to minimise any cracking and warping. 3. Finally there are the treated softwoods, which are generally cut, treated

and put on the shelf, leaving any final warping and cracking to be done in the garden.

As decking becomes more popular, more material will come to the market; making this an area to keep up with developments, so as to offer your clients the best options.

EXERCISE 6.3 Give two reasons why you might use decking instead of paving.

WALLING IN THE GARDEN Walling generally speaking comes in two forms: either clay or concrete. CLAY BRICKS Some of the more decorative bricks are found in this category, and there are


numerous ones to choose from. The big disadvantage with these bricks is that they are not all frost-proof, and will quickly deteriorate and crumble in damp wet weather. The only brick that is 100% weather proof is the engineering brick, which is a very hard clay brick. Because of this, it is often used underground or on the top of a wall as a coping. As for the others, the only way to be sure is to pay a visit to your local brick library or builders merchant and ask for their advice. CONCRETE BRICKS This category ranges from the standard concrete blocks up to some quite superb replicas of hand made clay bricks. The great advantage of this range is that they are all weather-proof, and can therefore be used anywhere in the garden without worry. FOUNDATIONS All walls will need a foundation, and there are several significant factors the garden designer needs to consider when putting one into the design. 1. A foundation is basically a trench filled with concrete. So let us consider

the consequences of erecting a shiny new wall along a boundary to hide the bottom of a conifer hedge, which is looking a bit thin and scruffy.

It sounds like a good idea, until you consider that when the trench is dug for the foundations, all the roots on this side of the hedge will be severed. This causes the hedge to either die or become extremely unstable.

2. As a rule of thumb, a foundation should be approximately one third the

height of the wall. For example, a metre high wall should sit on a foundation around 30 - 35cm deep.

3. Trees can pose a similar problem as a conifer hedge. However this can

be over come with good judgement and a little bit of luck. If a major root is found to be running across a foundation trench, it can be bridged using a lintel. It should never just be concreted around, as the root will eventually grow causing the concrete to crack and the foundation to weaken.

4. If you’re planning to plant against the base of a wall or you are

proposing to have paving going right up to an existing wall, it is a good idea to check that the foundation is well below the surface and not going


to interfere with any of your proposals.

HEIGHT AND THICKNESS

As you might well imagine, the higher a wall gets the wider it needs to be to keep it stable. As a rule, once a wall is higher than 1 metre high, it should be 1 brick thick or a half brick thick with pillars every 3 metres or so. The term half brick and full brick refer to the width and length of a standard house brick respectively (103 * 215mm).

FIGURE 6.9A: PLAN VIEW OF BRICKS LAID IN HEADER BOND

FIGURE 6.9B: PLAN VIEW OF BRICKS LAID IN STRETCHER BOND

FIGURE 6.9C: TOP AND FACE OF A FULL BRICK WALL BUILT USING HEADER (BOTTOM ROW) AND STRETCHER BOND


FIGURE 6.9D: TOP AND FACE OF A HALF BRICK WALL AND PILLAR

USING STRETCHER BOND

As you can see from the diagrams, when building a full brick wall you can create alternating patterns of header and stretcher bond, which can be used to create some attractive patterns.

However this will incur some additional cost, as it’s time consuming and uses more decorative blocks than the following alternative method.

If one side of the wall is not going to be seen, it is common practice to use concrete blocks in place of bricks. This is both quicker and the blocks are cheaper that the bricks. The only way to use header bond in this method is to cut bricks in half, which is OK for small patterns but becomes very expensive over large areas.

FURTHER INFORMATION

New materials and ideas are being developed every year, and a great way to keep in the know is to visit some of the larger shows that are on each year. If you find that your building knowledge is lacking, and you’d like to know how something is constructed, and any pros and cons associated with it, you‘ll find these shows have plenty of keen people glad to share their knowledge.

The Royal Horticultural Society is a good source of information, and should be able to point you in the right direction for shows in your area.


EXERCISE 6.4 To start up a portfolio of materials, collect the following: 5 types of gravel 5 types of flagstone 5 types of block paving 5 types of walling brick suitable for the garden For each of these items get details of: Cost per unit Sizes available Price per square metre, if available* *Some price lists will include a price per square metre for paving and walling. This is a useful figure to know for giving approximate costs to jobs. In your Workbook, you might like to set out your answer as below.

Material Sizes available Cost/unit

(ex.VAT) Cost per m2

Flagstones

Stonemarket 'Old

English'

600 * 600 4.10

600 * 450 3.26

600 * 300 2.70

450 * 450 2.45

450 * 300 2.13

300 * 300 1.94

450 * 225 1.62

12.10

Stonemarket

'Millstone'

30" * 30" 11.63

36" * 24" 11.17

NOW WATCH A VIDEO Choosing paving slabs and gravel http://www.youtube.com/watch?v=1QeABizZUQw


SUMMARY 1. You know how to define hard landscaping.

2. You are familiar with the various types of paving, and you know when it is best to use them.

3. You are familiar with other types of surfaces in the garden, such as decking and gravel: and know when it is best to use them.

4. You know how to use walling in your garden designs.


TODAY’S TASK The plan and elevation on the following pages show a newly built house on a new estate. Apart from a path to the front door, the garden has no paths, walls or decking. Your client is Anna McElvoy, who works for a merchant bank in London. She is out working during weekdays, but she would like to be able to relax in the garden, and entertain. She has no children, spouse or animals. Accepting that you haven’t got much to go on, suggest some ways in which paths and walls etc. could make her garden more interesting. You may draw your additions on to the plan. You might like to make a photocopy of the original plan, in case you don’t like your first efforts. Note that the plan is drawn on a scale of 1:200. Each grid is 1m x 1m in real life. On the plan, each grid is supposed to measure 5mm x 5mm, but the printing process may distort the grid size.


A PLAN OF ANNA MCELVOY’S NEW HOUSE (Scale 1:200)


AN ELEVATION OF ANNA MCELVOY’S NEW HOUSE


ANSWERS TO THE EXERCISES EXERCISE 6.1 Advantage: it is low in cost. Disadvantage: if used in areas of high tread, it will start to subside and become uneven. EXERCISE 6.2 1. If the deck is to be built above ground, you don’t need expensive

retaining walls.

2. You can lift sections, for access to drains and other services. Paving requires a more complex solution.

3. You can use small sections of deck around water to create simple bridges and jetties, with no need for foundations inside the pool.

6. paving and walls · flagstone paving this description may conjure up images of old stone paving,...

Documents