Edge Restraints
In order to keep your work ‘in bounds’, it is essential that the body of paving – small element as well as large – is confined by constructing or installing edging restraints at the time of construction, to ensure they are part of the ‘semi-monolith’ of the work. Some edges may be substantial e.g. a concrete or natural stone kerb as a bold statement and part of the visual design, whilst others may be discrete and invisible. Whichever you choose, the edging must be firmly fixed to prevent lateral movement or ‘washing’ of the material.
Granite setts may be employed as rustic upstands, using 100mm x 100mm x 200mm units laid end on i.e vertically, set into a substantial foundation of concrete, haunched with strong mortar to prevent movement. These may be recommended for use on driveways and car parks over soft clay ground. The cross sectional drawing shown below is intended for such a project, using resin bound gravel, on a clay soil site. Other materials may be block paving, brick paving or any other paver. What may seem overkill may be essential to prevent the edging setts from breaking away from the main body.
One method of creating an invisible edge, suitable for brick paving is to use roofing slates, laid on edge and set into concrete, with the haunching set well below the surface to prevent problems with turf dying off due to the amount of concrete causing issues with dehydration and heat scorch. The cross sectional drawing shows paving, although this method is invaluable for small element products including mosaics (see Mosaics and Tesserae) For extra strength, a double overlapped row of slates will withstand substantial lateral pressure without the need for any mortar in between the sheets.
There are various metal edges available in different strengths and heights, although they also may require inserting into a concrete foundation when trafficked by vehicles. Pathways and patios should not require the additional support of concrete, but as with any aspect of landscaping, it is always preferable to err on the side of caution when it comes to strength.
