When laying Bradstone Infilta concrete block permeable paving, conventional MOT Type 1 is not used in the sub-base as it is not free draining, the Bradstone 20mm open graded drainage is used. In free draining applications, a suitable geotextile should be placed at formation level (overlapping joints by 300mm), below the Drainage Aggregate sub-base. When the sub-base is designed to hold water an impermeable memebrane lining should be used. The depth of the sub-base will be governed by the strength & type of the underlying ground, but typically you will need to be around 200mm deep on soils of good strength & 500mm in areas of poor soil strength. It is best to prevent vehicles running on the sub-base during construction if possible, as they will cause rutting in the loose surface. The blocks are restrained in the conventional way with a kerb or edging & provide more than adequate support to traffic. Laid to a depth of 200mm, 1 Bulk Bag covers 2.85m 2 Laid to a depth of 500mm, 1 Bulk Bag covers 1.1m 2