The latest NHBC Technical Extra (issue 04 – 2011) draws attention to the need to maintain exterior wall dpc levels 150mm above ground level.An exception is made wherever a level threshold entrance necessitates a compromise. <br> <br> The Type LTT is a level threshold preformed dpc tray that removes risk, Cavity Trays says. Bedded in position it envelopes the masonry and wraps around the reveal skins. The arrangement protects and integrates with the adjacent wall dpc that is at a different level. <br> <br> Using a Type LTT promotes an easy standardised and economical way of constructing damp-free level thresholds, Cavity Trays explains. <br> <br> Type LTT ensures designed integration with both wall DPCs and vertical closers for consistent performance and compliance, it adds.