How deep should the laying course be beneath patio slabs?
The laying course beneath patio slabs is generally about 4 cm deep. Under DIN 18318, the permitted thickness is 3 to 5 cm, measured once the laying course has been fully compacted. The allowance for embedment or compaction must therefore be included during screeding; its precise extent depends on the bedding material and the laying method.
The sub-base beneath the laying course must be properly compacted and must not settle subsequently. At less than 3 cm, the laying course can no longer reliably accommodate dimensional deviations in the patio slabs or minor unevenness. It should not exceed 5 cm: an excessively thick or unevenly formed laying course may compact further in use, allowing the surface to sink in places.
The terrace is supported by a properly compacted crushed-stone sub-base. Larger irregularities must be removed before the laying course is screeded and must not be levelled out with a thicker grit layer.
Different aggregate gradings may be used as bedding material, depending on the paving slabs, loading and construction. In addition to graded crushed sand and grit mixes, certain crushed aggregates without fines may be used under the applicable paving standard. Suitability for the particular surface, grain shape, grain strength, water permeability and filter stability are decisive. Rounded aggregate is generally less suitable because it provides less interlock.
Because patio tiles made from rubber granules are elastic, their supporting surface must be particularly even and stable. For WARCO, the thinner the grit bedding, the better: it serves only for fine height adjustment and, depending on the tile type, should be about 0.5 to a maximum of 2 cm deep. A laying course of 3 to 5 cm, as commonly used for rigid patio slabs, is not suitable for WARCO tiles. Loose grit can move under loading, and elastic tiles follow depressions in the grit bedding.
In addition to graded crushed sand and grit mixes such as 0/4, 0/5 or 0/8, DIN 18318 also permits certain crushed aggregates without fines, such as 1/3 or 2/5.