Ivydene Gardens Case Studies:
Case 3 - Drive Foundations in Clay

Rainwater Drainage

Are you aware of the legislation that came into force on 1st October 2008 which affects the drainage of front drives? www.communities.gov.uk/ publications/planningandbuilding/ pavingfrontgardens gives government advice on driveway planning which you may find useful.

Front drives larger than 5 square metres are no longer allowed to discharge water onto the public road or into the domestic drainage without planning permission.

If you don't want to apply for planning permission at a cost of £150, the drive must be constructed of porous paving or a system such as channel and drain used to catch all surface flow and discharge it to a soak away (See Video from Marshalls on How to Install Driveways - Block Paving Installation) or other SUDS compliant facility on your own site. Point to note on Video from Marshalls, where they constructed a soakaway on site:-

  • If the ground is clay, then that soakaway will fill and never empty. In that case create that soakaway as a continuous one about 2 feet away from the boundary with it starting 3 feet from house and continuing round to meet the entrance of the drive, before planting privet or yew evergreen hedge in that 2 feet gap between it and the boundary to absorb the water from that driveway. The 2 feet depth of existing clay soil between that extended soakaway and the boundary should be replaced by the following mixture of 1 part existing soil and 1 part sand to provide a soil where the soakaway water can move from the soakaway through the soil to the hedge roots. The french drain used to transport the water should be surrounded by 4 inches of coarse pea-shingle inside an envelope of geotextile to stop that pea-shingle from mixing with the mixed soil.

If you construct any paving that directs the rainwater off your site, then this could delay or even stop a house sale - see Interpave for the latest information


The following drive collected all the water and drained it to climbing roses alongside the drive. Even though the subsoil is clay, there has been no complaints of the system getting overloaded during the last 16 years.

Cedagravel® provides an excellent low maintenance SUDS compliant surface suitable for paths, drives, car parks, caravan sites and lorry parks.

Cedagravel® has been through extensive research and development to bring you the very best gravel stabilisation system on the market. The large sheets of 2.15m x 1.14m x 40mm are fitted with a geotextile underside and has been tested to 300 tonne when filled, which makes Cedagravel® extremely tough and very quick and easy to install. Further details at bottom of this page.


I have used this product for paths, driveways and patios. In order to provide a patio without losing a section of lawn, I have laid Plantex with Cedagravel on top, filled it with loose earth, watered it, spread grass seed, filled again with earth and watered it. It then became a lawn that outside chairs and tables could be laid on without deforming this new lawn.


Drive Foundations

If the foundation for a drive is incorrect, then vehicular access can deform it. If there is no foundation under a pedestrian path or patio, the surfacing layer can be raised/lowered by the weather.

Spon's Landscape Handbook provides an overview for those involved in landscape planning, design, construction and management:-

The layers of material that make up a full-scale road are:-

Substrate or Subgrade: natural or engineered ground level.
Sub-base: main structural and levelling layer.
Road Base: secondary structural and levelling layer ( not usually neccessary in domestic drive, pedestrian path or patio work)
Surfacing: the finished surface that carries the traffic.


When dealing with sub-bases, the soil (substrate) can be divided into 6 types and 2 categories depending on the level of the water-table. Each type and category is given a California Bearing Ratio percentage number (CBR). A geotextile (like Plantex) filter membrane should be laid between the substrate and the sub-base.

See below this plan and photos for remainder of this technical note.


drive 1 proposed plan and breakdown of costings incurred

Concrete and rainwater soakaway trench excavated. Weatherboarded fence removed.

drive trench for rain drainage picture

The perforated drainage pipe was surrounded by 8mm peashingle (supplied by Allsand Supplies Ltd), which was enveloped in Plantex (Plantex is a geotextile used to separate materials from combining with each other and is available from Travis Perkins builders merchants). 6 Gully covers with chamber risers filled with planting compost were placed on top of this drainage pipe, so that the climbing roses inserted in that compost would have a water supply from below.

Clay excavated. Perforated Drainage pipe installed in trench with 1:40 fall from garage to drive entrance.


drive clay removed to depth required for drive foundations picture

Concrete edging and foundation was installed

drive edging and drive foundation installed picture

Concrete edging was installed to stop the sand from migrating. It was haunched with concrete on each side for strength. 6" deep of Type I Roadstone was placed on top of Plantex as foundation. The fence was created and installed by Jacksons Fine Fencing to my specification. I installed the gree plastic coated chainlink fence to provide a climber support system for the Zephirin Druin thornless climbing roses.

Zephirin Druin climbing rose installed in planting compost and mulched with peashingle.

drive rose in pea shingle to use drained rainwater from drive picture

Small Child-proof side gate and path installed by Jacksons Fine Fencing.

drive sidegate and path completed picture

Coarse Sand was laid and compacted before the pavers were installed, kiln dried paving sand was used to fill the gaps between the pavers and these were then vibrated down.

The completed drive.


drive completed looking up to road picture


The completed drive in June of the following year

drive 1 year on picture



The sub-base is the main layer of material that forms the structural foundation for the drive, and establishs the pedestrian paving or drive level. For domestic use, the sub-base material alternatives are: a solid concrete base, a cement bound sub-base, or a granular sub-base.

A granular sub-base as used for this drive (and I use under paths and patios as well) consists of aggregate to the specification of Department of Transport Type I. I use the crushed rock alternative, which must pass a 75mm sieve, and be free from dust or any pollutant such as oil or other chemicals.

The thickness of the sub-base is determined by using the California Bearing Ratio percentage number (CBR) from the table below in the

Estimated sub-base Thickness Table.

Soil Type

Plasticity index

CBR for Water-Table more than 600mm down

CBR for Water-Table less than 600mm down


Heavy Clay





Silty Clay





Sandy Clay















Sandy Gravel





The Plasticity index indicates the difference in the moisture content of a soil when it is neither too liquid nor too dry to be plastic.

Estimated Sub-base Thickness Table


Footways, patios, garden paths, house parking (mm)



















7% and over





I used a 150mm thick sub-base for average clay conditions, then 50mm thick of compacted sharp washed sand complying with Table 2 of BS 6717 Part 2 (BS is British Standard) followed by laying 60mm thick concrete pavers on top. These were then vibrated down with 6 bags of dry paving sand to lock the pavers together.

Construction Notes:-
19 cubic yards of clay, concrete and fence required 6 six cubic yard skips. These are currently £151 each.

These materials had to be excavated by hand and removed by wheelbarrow due to the clay main drain 6" below the concrete surface, with brick manhole walls, lead mains water pipe alongside the house wall and yellow gas pipe across the drive and 1 foot below and no access allowed from next door's drive.

Instead of using 10" wide joists as a skip ramp, I would recomend the use of Load-Eze for safety reasons



CedaGravel Stabilisation System from CED Natural Stonecedagravel6

The Stability of Paving with the Versatility of Gravel for the following benefits:-

  • Low Maintenance
  • Quick and Easy Installation
  • Only 5-6 Cm of Gravel
  • SUDS Friendly, Allows Drainage
  • 100% Porous: Reduces Flooding and Ground Water is Replenished
  • 100% Recycled and 100% Recyclable Polypropylene
  • Geotextile Underside Inhibits Weed Growth: Less Herbicides
  • Easy Driving, No Pits, Ruts or Puddles. Ideal for Driveways
  • Wheelchair and Pushchair Friendly
  • Easy and Effortless to Walk on

and the following properties:-

  • Material Polypropylene
  • Sheet Dimensions 2150 x 1140 x 40mm
  • Honeycomb Diameter 37mm
  • Strength at 20°C 300 tonnes filled
  • Drainage Capacity 100% Porous
  • Biological Resistance Excellent
  • Chemical Resistance Resistant to almost all chemicals
  • Thermal Properties Resistant in temperatures from –40° C to
  • +80° C
  • Weathering UV Resistant



Installation Guide written by CED




As with all other types of paving start with a good foundation. If your application calls for vehicular access lay a sub-base of compacted MOT type 1 (or possibly hardcore) to 100mm-150mm in depth and cover it with a layer of 20-40mm deep layer of sharp sand. This must be compacted and flat before the sheets are laid.





Paths and pedestrian areas can be laid on top of compacted sharp sand without a sub-base, again approximately 20mm-40mm in depth, again compacted and flat.


Place the honeycomb sheets over the prepared ground. cedagravel3The geotextile underside helps inhibit weed growth, and should be over-lapped at sheet joints. When two sheets meet up tuck one of the flaps under the sheet and place the sheets close together over the whole area. The honeycomb can be easily cut with a power or hand saw to meet the outer shape required. A larger number of sheets can be laid in minutes due to their light weight and ease of handling. The sheets do not require clipping together or fixing down.


The edge of the honeycomb area needs to be retained. This can be done using existing walls and buildings, stone setts, kerbs, timber, metal edging systems etc. The edging needs to be laid so that it is proud of the finished gravel level by at least 20mm.


cedagravel4Lastly, the honeycomb is then filled with gravel to the top, with a further 10-20mm to conceal it. No rolling is required. cedagravel5

Important note: Avoid heavy loads on the unfilled honeycomb during installation.

CED LTD, 728 London Road, West Thurrock, Grays, Essex. RM20 3LU


Tel: 01708 867237, Fax: 01708 867230, CED Natural Stone

My brother used the system on his new front drive, building it himself in February 2015:-





When it rains, then the water drains through the cedargravel into the sand/hardcore underneath instead of draining onto the pavement and thence to the road. That extra water would if allowed to drain onto that public road possibly cause flooding of that road or other people's property further down the road.

Because the pea-shingle fills separate containers, it is possible with careful placement to create either a Hopscotch playing area or a layout for Snakes and Ladders. The Hopscotch can also be used by us geriatrics for excercise periods and the Snakes and Ladders for slower walking excercise, instead of only children playing the respective game!!


Site design and content copyright ©December 2006. Page structure amended October 2012. Chris Garnons-Williams.

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Case Studies *

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Topic - Wildlife on Plant Photo Gallery


Case Studies Pages
Site Map

1 - Prepare for Sale
2 - Structural Design
2a - New Garage
3 - Drive Foundations *
4a - Garden Uses
4b - Garden Plant Plan
5 - Wildlife Garden
6 - Vegetable Garden
7 - Repair of Concrete Pond
8 - Creation of Pond

Design Cases

When designing a garden, it is vital to know who and for how long the resulting designed and landscaped garden is going to be maintained by. The book 'The One Hour Garden' describes what maintenance work can be done in the time that you have allotted; and therefore what besides a lawn, you can have in your garden. My redesign and construction work to be done on my 3 gardens - as shown by Case 2 - must be to reduce the maintenance time required to the time I have available. If the gardens are first weeded, pruned, mulched, mown and bare earth converted to lawns using grass seed, then construction can take place in the future - as free time allows during a week or fortnight after the maintenance has been done.

In Case 4, the combination of the Structural and Planting Designs would create a garden that I would be able to maintain in one day a fortnight. I would install a 3" deep mulch in the spring on the beds, so that I can prune the shrubs/trees and hoe the odd weed; whilst the father mows the lawns, the mother tends the vegetable garden and their teenage daughters play football!!

The children in Case 5 loved to look at creepy-crawlies and wildlife, so that together with low-cost the design for different areas in a terrace house garden was created.


Construction Cases

Case 3 is building a drive on clay and it is important to get the part you will not see - the foundations - done correctly.

Case 8 is creating a pond with its pitfalls for foundations.


Maintenance Cases

If you are asking someone to maintain your garden, then do provide the complete picture. If as in Case 1, you intend to sell the property, then look at this - as not a maintenance but as a selling job - and get that job done instead.

Case 6 is creating a vegetable garden in a back garden during the maintenance program of one day a fortnight to maintain it and the remainder of the back and front gardens. This was done over 7 years using a crop rotation system

Concrete ponds are likely to crack open due to movement in the ground levels due to being in clay or vibration caused by road traffic if it is fairly close. Case 7 shows no planting shelves for the pond plants.

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