Type U Undersill Envelopment Tray Cavity Trays - Cavity TraysType U Undersill Envelopment Tray Cavity Trays - Cavity Trays

Type U Undersill Envelopment Tray

  • Prevents damp permeating inwardly.
  • Integral end upstands.
  • Integrates with reveal DPC.
  • Satisfies LABC 7.4.13.
  • Satisfies NHBC 6.1, table 9.


Undersill Envelopment Trays provide the requisite DPC presence in and around stone, concrete and jointed solid sills when incorporated within cavity wall construction. Manufactured from solid polypropylene, trays extend up the back and ends of the sill, and pending the construction detail, return either immediately under or a course below the sill base.

Envelopment ensures DPC interruption to block damp permeation as defined within NHBC 6.1-s4 d: ‘Where a jointed or permeable sill is used (all sills in Northern Ireland and the Isle of Man), a DPC should be placed between the sill and the outer leaf, turned up at the back and ends of the sill.’ LABC / Premier Guarantee 7.4.13.

Misplacement and DPC distortion can be eliminated using preformed Envelopment Sills that ensure the protective inclusion is consistent in shape and functionality. The tray end upstands cannot sag like flexible material and permit the reveal closing arrangement to positively integrate.

Envelopment Sills can be supplied incorporating a thermal break bonded to the rear of the cavity upstand. This option can be appropriate where there is no cavity wall insulation present. Envelopment Undersill Trays are supplied to customers dimensions.

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