Dimensions & Thickness of Paving
It is important that the thickness of a chosen paving slab or type is taken into consideration when planning a project, taking every aspect of the job into the equation, especially load bearing and amount of anticipated use. In residential projects, unless occasional heavy vehicles are expected i.e. oil delivery lorry, dustcart etc, 75mm for most types of paving should be sufficient to cope with the site. (See Driveways Depths of Foundations.)
For most domestic patios, paths and seating areas, 20mm paving should be adequate, bearing in mind the anticipated amount of use, and the ground/soil conditions. The most important ingredient in a successful paving project is the bedding mortar base and sub-base. The actual strength of the paving material is secondary to adequate preparations.
Problems may occur when opting for large size slabs – 600mm x 900mm, 900mm x 1200mm etc. @ 20mm thick as these will have a tendency to twist and flex during laying operations, and this may not manifest itself until extremes of temperature may cause them to shift in their bed, even when firmly and properly laid over a strong laying bed and fully slurried backs, due to their lack of integrity as a unit.
Be aware of mixing different thickness materials, unless they are firmly secured within their own beds and bedding mortar. Blending 20mm paving with 100mm granite setts for example, is fine provided that the depth of the project allows for a substantial bed under the setts, which means increasing the laying bed under the 20mm slabs to compensate for the difference.
Similarly, adding a decorative row of different thickness (100mm) setts or paving to form an edging to a 20mm patio will require a method of tying the two materials together, otherwise the outer row will become detached from the main area. In these instances, either include reinforcing mesh under the 20mm paving, extruded out to support the 100mm setts, or alternatively, add stainless-steel brick ties into the laying bed of the paving and ensure they reach out to support the edging setts. (See Edging Restraints.)
