EWI Service duct within Insulation - flush face

Author details

Original Author:Admin Organisation:Retrofit Pattern Book

Detail summary

A detail demonstrating a recessed, insulated services run for an exterior wall, within an external wall insulation system. Used where service runs such as soil pipes or ventilation ducts are to be contained within the depth of the insulation, meaning an accessible service void should be created.

Prior to work carry out a visual inspection of the services to be enclosed within service void, to ensure in sound condition before constructing service void.

Technical description

Plan detail. EWI. Service duct detail, flush faced. recessed original pipework.

Reference Specification:

Fibreboard specification:

  • Hardboard: To BS EN 622-2.
  • Medium board: To BS EN 622-3.
  • Dry processed boards (Medium density fibre board): To BS EN 622-5.
  • Particleboards: To BS EN 312.


  • Appearance class, hardwood: To BS EN 635-2.
  • Appearance class, softwood: To BS EN 635-3.
  • Bond quality: To BS EN 314-2.

Plastics veneered board: To BS 4965.

  • Laminate grade: VG.

Care should be taken to ensure air-tightness. Seal all service penetrations. Lap and tape all membranes.

All insulation to be continuous to avoid thermal bridging.

Preparation of external wall: Remove any existing loose material and prepare in accordance with manufacturer's requirements.

Any alterations to drainage and other fixtures, or work to prepare the substrate, to be agreed with contract administrator prior to work being undertaken. Prior to start on site inspect: form and condition of the structural substrate; institute repairs and/ or additional works necessary to make the substrate suitable to receive EWI system.

Parts list

  • Treated softwood studding [EW03b]

    • Strength class: C16
    • Species: Contractors choice.
    • Size: as detail/ to suit depth of insulation.
    • Stud centres: As detail/to suit services to be boxed in.
    • Fasteners: Framing anchor.

    Contractor's choice.

  • Flexible woodfibre insulation to service void [EW03b]

    UdiFLEX woodfibre insulation.

    • GWP: 0
    • Thickness: to full depth of insulation.
    • Installation: Friction fit between services to avoid thermal bypass and ensure high thermal performance.

    Unger-Diffutherm. Product Reference:Reference: UdiFLEX
    Supplied by: Back To Earth.
    Tel: 01392 861763
    Web: http://www.backtoearth.co.uk/

  • Render carrier board (to form access panel)

    GTEC render board. Screwed to timber frame

    Siniat. Product Reference: Aqua board

  • Access panel insulation

    External insulation wall board. 50mm nominal thickness (to suit void depth). Adhesive fix.

    Kingspan Insulation Ltd. Product reference: Kooltherm K5 External Wall Board.

  • Hardwood trim to edge of panel

    • Manufacturer: Contractors choice.
    • Type: as drawing
    • Finished size: as drawing.
    • Species: as drawing.
    • Class: Class 1 to BS 1186-3.
    • Preservative treatment: Boron as section Z12 and WPA Commodity Specification C10, service life 30 years.
    • Finish as delivered: Natural
    • Fixing: Countersunk screws and 400mm centres.
    • Certification: all timber to be FSC certified.

    Contractor's choice.


  1. Admin - 2015-04-29 16:39:48 [Displayed version]

    DWG uploaded. Contact details for [EW03b] updated.

  2. Admin - 2015-03-20 16:00:35

    Version 1 - Detail added.

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  1. For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.

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