Whilst Permadeck20 is bonded to its own plywood deck, making it one of the most reliable waterproofing systems available, some roof designs require a ‘loose-laid’ system. This is PermadeckSL. SL stands for sub-layer. As can be seen below, sub-layer systems are used with concrete and inverted balasted roofs. At ground floor level this can be a tanking system and at roof level for heavy duty screeded walkways or inverted insulation designs etc. The main advantages of PermadeckSL is that it is completely seamless and, lying on a slip membrane, immunised from slab movement and cracking.
The beam and block structure should be nib-free and any dips and hollows >10mm should be screeded out.