Application

  • To prevent damp ingress inwardly via stone, concrete and jointed solid sills.
  • Traditional and timber frame construction compatible.
  • New work applications. Retrofit possible with reconstruction.
  • For site-formed tile and brick sills, see Type U Undersill Tray.

Description

Bespoke Undersill Envelopment Trays provide the requisite damp proof course (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.

The tray can finish flush with the exterior face or project forward of it in the form of a small lip as defined in LABC/ Premier Guarantee 7.4.13. State option required.

Where movement provision is required, soft infilling pointing is commonly recommended in a sill bed course and a projecting lip can assist soft pointing location and retention of such pointing.

Forticrete and other cast sill manufacturers sometimes recommend a slip-plane is incorporated with their products to accommodate possible (thermal co-efficient) movement. Where the specialist reconstructed stone sill supplier makes this recommendation, consideration may be given to using a cavitray slip-strip to accompany the Envelopment tray. The slip-strip is laid into the base of the tray and has one textured face and one smooth face to provide the requisite relationship. Consult manufacturer for further details.

Features and benefits:

  • Prevents damp permeating inwardly.
  • Integral end upstands.
  • Integrates with reveal DPC.
  • Satisfies Local Authority Building Control (LABC) 7.4.13.
  • Satisfies National House Builders Council (NHBC) 6.1, table 9.
  • Cavity insulation does not affect tray placement position.
  • Does not extrude or compress under load.

Applications:

  • To prevent damp ingress inwardly via stone, concrete and jointed solid sills.
  • Traditional and timber frame construction compatible.
  • New work applications. Retrofit possible with reconstruction.
  • For site-formed tile and brick sills, see Type U Undersill Tray.

General information

Size

As drawing

Insert drawing number.

Uniclass 2015

Pr_25_57_21_66 Preformed cavity traysPrimary

CAWS

F30/270 Meshwork joint reinforcement

F30/56 Preformed cavity trays

Specification data - Preformed cavity trays

Product Reference

Type U Envelopment Tray

Size

As drawing

Insert drawing number.

Standard product features

Technical characteristics:

  • Material: Sill: Polypropylene. Thermal insulation: Inskorfoan polystyrene to BS 3836. Thermal conductivity (K-Value) 0.033 W/m·K.
  • Colour: Black.
  • Dimensions: Standard 2440 mm in one length (maximum).
  • Cavity width: 50–200 mm.
  • Masonry skin styles: No known limitation – flat finishes.
  • Undulating masonry faces: Compatible.
  • Curved wall on plan applications: Yes (see manufacturer's literature for details).
  • Arrested water evacuation: Integral transient drainage apertures.
  • Thermal transmission of material: Negligible.
  • Jointing method: Glove lap 150 mm if over 2400 mm long.

Literature
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