There has been a lot of comment lately regarding materials for projects. Should we, as contractors or designers be expected to nominate or offer to source products, or should this be the responsibility of the client (or Architect/Specifier) ?
I really think that the selection and final decision should rest with the Contractor, who is being asked to use the products. After all, it something goes wrong – and I can certainly think of examples when two natural stones laid side by side on a project reacted chemically in a fairly violent manner, with one contaminating the other within a few weeks of build. (e.g. colours fusing together, or calcium build up between two types of ‘rockery’ stone used in a water feature, creating an unsightly mess and eventual cracking the water proofing of the scheme).
If you are not involved in specifying, or are asked to work with materials outside your current experience, ensure that this fact is noted in your contract documents.
There are so many different Landscape materials available nowadays, with man – made products and natural stones, timber in great variety, plus a host of special ‘new’ materials, usually premiered at Shows by designers and suppliers, – many of which have not stood the test of time on site in the garden – and with clients becoming more aware of these products via television and the internet, a Landscaper almost needs to be an expert in ‘materials’ to keep ahead of the game!
As a contractor, it is most important that you ensure that the clients clearly understand the materials and products that you intend to use in their garden –either selected by themselves, their designer or nominated by yourself.
There should never be any room for doubt, or to allow channels of communication to break down, and find that you have supplied or arranged delivery of products that have not been formally approved by the client or agent acting on their behalf.
This formal approval is best dealt with by what I refer to as The Products Library.
As a main part of your quoting process, you will have nominated, or received instructions from the designer, a number of construction materials, probably, but not exclusively, including top soil, bricks, stone walling and paving, concrete slabs, plants, turf, timber and aggregates.
Whilst many will have been selected from catalogues or magazines, perhaps with samples of actual product, you will need to produce the complete range of materials to show the client, and retain these products on site to be referred to in case of queries.
These samples should be delivered before placing an order and an inventory, including full description, catalogue reference numbers and any other identification to completely remove any doubt, should be made.
As with most hard landscaping materials, especially paving and bricks, the colour variation between wet and dry can be enormous. Always show the product wet and dry to ensure that the client accepts these variations.
On several occasions, I have known the client to reject a delivery of product (usually paving) when it arrives as it was not the colour they chose. The reason for selecting and agreeing a reference number is to avoid any confusion when describing a colour in words. To some people, the description ‘natural colour’ will mean grey, to others it will be the colour buff.
When you have all the main products together on site, they should be kept together as a ‘library’ to be referred to if required. The actual properties of some materials may need to highlighted. For example, I have known cases where sandstone rockery stone has been rejected – even after approval by all parties – once the scheme had been completed (!) because the ‘dust blows into my dog’s eyes’. The whole rockery had to be taken apart and different stone used at the expense of the contractor, because they had not explained the nature of the stone.
Plants will not normally form part of the Product Library, as by their nature, they may not be able to be kept on site during construction works. If, however, you are called upon to provide a sample of a hedging plant (for example) or other plant which will be used in the ‘construction’ e.g. the boundary/fence line, do ensure that you order sufficient plus some extras. A contractor who supplied 120 Laurels to site, 1.2m high in 10 litre pots, was asked to supply an extra run of 20 plants. The second batch were the same height and pot size, but greener and bushier. The client demanded that the original 120 were replaced with the greener, second delivery plants. (ouch!)
I will describe some of the more common materials in landscape construction schemes, majoring on the types of issue that crop up on site. Having worked in most parts of the UK, I appreciate the pretty wide variations in hard landscaping materials and aggregates, and I am mindful of those differences when commenting.
There are two main types of brick for use in a garden – paving and walling. Both disciplines require different types of brick, and manufacturers producing both will give you technical details for their uses, including their limitations.
Generally, bricks are delivered in packs of between 400 and 500 in number. If you require more than one pack of either for the project, you should draw from two or more different packs when barrowing them from pack to site, to ensure that any slight colour variations are ‘mixed’, and will not show as a different colour from other packs.
If you do not mix the packs, you may well find a colour banding – especially when building a wall – will appear as construction progresses. This is not a ‘defect’ as such, but a pigmentation variation within tolerances from the manufacturing process.
Paving bricks (BS 4729)
These are usually manufactured without a ‘frog’ or recess for mortar, and vary in thickness between 50 and 100mm. They are especially manufactured to be denser than walling bricks and to a greater crushing strength, to enable them to be used in driveways. Providing the sub – base and base are solid enough, brick paviers will cope with lorries – including oil delivery lorries which sit in one place for several minutes with the engine running, the whole machine acting as a vibrating plate – without any damage.
Some paviers are manufactured with a small ridge on their edges, to enable close fitting whilst at the same time permitting silica or jointing sand to be brushed into the resultant intercises. Others are smooth edged to a high standard of uniformity, to permit highly complex and technically difficult patterns to be formed. Some are irregular, with slight curves and a rough surface to be used in less formal designs.
All bricks manufactured for use as paviers will be fit for purpose, but it is worth obtaining all technical information for use both in your quotation, and for future reference. There are some excellent publications available, without charge, from manufacturers such as Ibstock and Freshfield Lane Brickworks, showing a wide range of products, their uses and full specification.
These are usually manufactured with a ‘frog’ to allow the mortar bed to be thicker in the centre of the unit. They come in many different colours and styles, from Blended Farmhouse (old fashioned and traditional) to modern, clinically perfect units. As with paviers, manufacturers will supply you with full technical information, including their uses i.e. below ground – frost proof – porosity and density – tolerances – heat tolerance etc, to enable you to make an informed decision when specifying.
When constructing a wall, colour batching of the mortar is critical, as even the slightest variation in colour will show as a defect. I use pots or buckets as a measuring gauge, filling a certain number of sand to cement for each mix.
Pre – cast Paving BS EN1339
There is an extremely wide selection of manufactured paving on the market.
The variety of shapes and sizes will prove more than a match for any designer.
Most slabs will be made of wet concrete, although some may be manufactured using compressed sand/aggregate.
Thickness will vary between 37mm and 75mm, with dimensions between 15cm x 15cm to 90cm x 120cm. Once again, crushing strength will need to be considered if it is proposed to use a paving slab in a driveway. You may consider using a small element precast slab – block paving – as an alternative.
I suggest a Brindle or charcoal shade for car parks and drives, as they will not show oil stains and drips as much as a uniform lighter colour.
Cement BS EN 197 – 1
We usually use ordinary Portland cement in landscaping works, although some works may require specialist cements. In such cases, you should expect the designer or specifier to nominate and if necessary, arrange for delivery.
Ensure that whichever cement to choose to work with, do not change manufacturer or brand name. Stick with the same cement throughout, as there are distinct colour variations to some products. Perversely, I find that the darker the dry cement powder, the lighter the dried mortar colour becomes.
(One small aside here, if you are using premix mortar or bulk delivery concrete, and it starts to be become unworkable due to time or hot weather factors, by adding water – the logical thing to do – you actually speed up the hardening process, water being the accelerant in the hardening of concrete!)
Top soil BS 3882 (2007)
Topsoil must be ordered to conform to BS 3882. This is very important, as some of the material cited as ‘top soil’ – even shown as such on the one tonne big bags at the merchants – may in fact be green waste. This is not top soil!
You may be required to supply screened sterilised top soil, in which case you will need to see a certificate stating its pedigree. Such soils are relatively expensive, and will add considerably to the project costs.
If you are working on an organic site, you will need to see a Soil Association certificate for each load that is delivered to site.
There are three main topsoil types, the first being referred to ‘as dug’ which implies that it is literally, straight from another site, with natural humus and small tree roots etc, but substantially free from pernicious weeds etc.
Type two is called screened topsoil, which is a mixture of topsoil, small stones, some sand, with variable organic matter.
Type three is known as manufactured, which is a mix of good quality topsoil mixed with some green waste compost and organic matter.
Nursery Stock BS 3936
Nursery stock should be to BS 3936 as a matter of course. Each plant, or batch of plants should have a Plant Passport number, which should be noted for future reference in case of problems e.g. vine weevil or disease.
Check the quality of the stock for stem and root damage, removing some pots if necessary. All pots with pot bound roots or weedy compost (and couch grass in the pots/roots) should be rejected outright.
Turf BS 3969
There are a wide range of grass turf varieties available. It is not always wise to buy the very finest quality turf, unless the client is prepared to spend a lot of money on aftercare treatment.
On some sites, you may have to match existing grass/lawns. It should be possible to arrange a site visit by your local supplier who will advise you of the nearest option. Such specialist advice should be acceptable to the clients and their agent.
It is often preferable to use a slightly lower grade of harder wearing turf, and feed and nurture that product to become ‘localised’ rather than try to force the garden to acclimatise to the turf!
All timber is expensive due to the high costs of manufacture, shipment and storage. It is also becoming scarcer, with a large volume being used in heating systems (as pellets) and various manufacturing processes involving mass market furniture, especially in the developing ‘Tiger’ countries.
Except for relatively small number of specialised schemes using Iroko, Teak, Quila and other exotic hardwoods, the Landscape industry normally relies on Oak and Cedar for hardwood projects and a range of Pines for other works.
Most timber, certainly new materials, will carry a ‘renewable resource’ label indicating that it is ‘green’ to use such timber. English Oak in good quality is becoming harder to find, but there is still a steady supply of French grown Oak available.
Storage on site is the biggest issue from the landscapers viewpoint, as wet or hot weather will cause splits or ‘shakes’ in the timber, making the planks or sections unworkable. The timber should be stored raised from the ground and heavily sheeted. Place timber battens between the layers of timber if necessary.
Accurate sizing or dimensioning of timbers is becoming an increasing problem. Due to tolerances permitted by the timber industry, the actual sizes of the materials can vary by as much as 5%, which causes many problems if you are using them in restricted situations i.e. as raised beds or retaining walls with upright supports to the rear. When you offer up a timber section (sleeper) to the backing plate, the thickness variations will show up and spoil the whole professional effect of the job. Very annoying, so ensure that, once again, you buy sufficient material to complete the job, plus a bit extra!
Paving – Natural materials
There appears to be an ever increasing range of natural stone products on the market, which, as a natural stone fan, I warmly welcome. There can never be too many for our industry!
A few words of caution only, as there are so many, it would be impossible to even mention the range and possibilities for design.
York stone – reclaimed
Please beware that there is still a large amount of stolen York stone flags on the (black) market. All reputable suppliers know the source of their purchases and actively discourage the sale of unknown origin materials.
Beware too, those flagstones that have been jet washed or sand blasted. They may be presented to you as ‘reclaimed’, but in probability were previously used in factories, manufacturing heavy industry, and are in fact thoroughly soaked with oil or other chemicals. Once laid, and subjected to sunlight and heat, these oils will come out of the slabs, creating an almighty mess!
York stone – new
York stone is available in a wide range of sizes, some sawn six sides to a high degree of accuracy (plus/minus 3%) by diamond blades, and to a lesser extent, shot sawn with lead shot and water.
(Please do not be concerned by minor score marks on sawn slabs. This is all part of the manufacturing process, and occur when the blades are withdrawn.
They are not a ‘defect’ and should not be treated as such).
Flagstones are also available with hand fettled (non – sawn) edges and a riven or split face. Again, these are available in a range of sizes. Do not worry about comb or chisel marks on the surface. These are the marks of the mason as he sets about dressing the stone.
Beware those flagstones that appear to be delaminating, or splitting along the thickness of the slab. These may have been sourced from a shallow quarry, and will not have endured the massive crushing effect of millions of years of being buried in a deep cast quarry. These are often offered at a lower price, but are not good value for money – unless you are using them in situations where splitting is not an issue e.g. stepping stones.
I will include the recently introduced (since 1989) Indian sandstone paving stones here, as they are in many ways similar to riven York stone. Both are quarried in the same manner and have similar properties vis a vis crushing strength, porosity and density.
The wide range of colours, and reasonably uniform thickness of the slabs makes them very attractive to landscapers. Prices are very competitive, some ludicrously low considering they have been transported all the way from India.
A low purchase price may well disguise a much higher laying/labour price however. A good quality product will be carefully gauged to allow for laying to a random pattern (or pre – cut feature e.g. circle) including the pointing joint.
Cheaper slabs will have been cut by guillotine and ‘sheared’ into sizes that are half or a quarter of a larger slab, with without allowance for a pointing joint, requiring each slab (to give a professional finish) to be cut to a smaller size, which is not a saving at all!
With all materials, even those you have had many years of experience in working with, are subject to change, either in dimension or specification, and it worthwhile keeping yourself fully up to date with these changes.
Contact all those manufacturers and suppliers of materials and products that you enjoy using – we all have our personal preferences – and ask to be placed on their mailing list, both for prices and technical information. They are an invaluable source of knowledge, which will certainly stand you in good stead with both designers and clients alike.
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