EWI around meter box with perimeter insulation

Author details

Original Author:Admin Organisation:Retrofit Pattern Book

Detail summary

EWI detail around existing meter box, where perimeter insulation has to be provided around the base of an external wall, due to excavation work around new/existing gas pipes, in order to mitigate cold bridging.

Because of the the need to keep a required distance around gas meters and pipes as part of EWI works, it is recommended that Internal wall insulation be installed at a future date to the internal wall behind the existing meter. A 300mm overlap to the EWI on the external wall combined with insulation works to the existing ground floor is expected to mitigate cold bridging caused by carrying the EWI around the meter box.

Technical description

Section detail. EWI around existing meter. Perimeter insulation provided at foot of external wall around existing pipework. Grouted in place and capped. Base plinth detail to EWI above ground level. Internal wall insulation to be installed in future to reduce cold bridging around meter.

Suggested Insulation Sequence:

  1. Excavate channel to depth of surrounding excavation.
  2. Fix bracket.
  3. Install lightweight glass aggregate granules into channel for insulation.
  4. Lay paving stone.
  5. Attach door frame to box and fix in place and tape.
  6. fix external wall insulation.
  7. Render

Reference Specification:

Refer to Approved Document P: Electrical safety- Dwellings for works involving Meter boxes and electrical inlet.

Drainage below ground guidance can be found in Approved documents C, section 3; and Document H, sections 2 and 3 for rainwater drainage.

Drainage layer: Granular infill free from excessive dust, well graded, all pieces less than 75mm in any direction, minimum 10% fines value of 50 kN when tested in a soaked condition to BS 812-111. In one layer no more than one of the following:

  • Crushed rock (other than argillaceous rock) or quarry waste with not more binding material than is required to help hold the stone together
  • Crushed concrete, crushed brick or tile, free from plaster, timber and metal.
  • Crushed non-expansive slag
  • Gravel or hoggin with not more clay content than is required to bind the material together, and with no large lumps of clay.
  • Well-burned non-plastic colliery shale.
  • Natural gravel./Natural sand.


Care should be taken to ensure air-tightness. Seal all service penetrations through EWI and existing wall. Lap and tape all membranes around edges of EWI system.

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 the form and condition of the structural substrate; institute repairs and/ or additional works necessary to make the substrate suitable to receive EWI system.

Existing gas meters and inlets are to be left in-situ. Insulation to be fitted round them as closely as possible, whilst ensuring they are still properly ventilated. Care should be taken when excavating close to gas mains.

Parts list

  • Lightweight Aggregate Insulation bounding layer [FL03]

    Lightweight recycled glass aggregate.

    • Thermal conductivity: 0.08W/mk
    • Depth: As per detail
    • Width: 200mm.
    • Installation: As technical specification. Taking care not to damage gas pipes and services during installation.
  • Concrete Flag Paving over drainage layer [FL03]

    • Manufacturer: Contractors Choice.
    • Size: to cover drainage layer.
    • Finish: smooth
    • Colour: Natural
    • NBond: Half lip staggered.
    • Jointing: N/A

    Contractor's choice. Use reclaimed paving where possible.

  • EWI (Woodfibre) System,Rendered Finish [EW01]

    Composite woodfibre board for use on solid and hard to treat cavity walls.

    • Insulation back board: 100mm UdiTherm SK.
    • Insulation top board: 100mm Diffutherm NF (T&G, renderable).
    • Thermal conductivity: 0.045W/m2K. GWP 0.
    • Base Coat: levelling on substrate: 90% contact required around edge of boards between board and substrate to prevent thermal bypass. If substrate is very uneven, use base-coat material around edge of board to achieve contact.
    • Fixing: Fixed mechanically to substrate in accordance with manufacturers recommendations.
    • Render/carrier: to manufacturers standard.
    • Render: Udi Perl
    • Decorative finish: tbc
    • System guarantee: 25 years - ECO compliant insurances and guarantees.
    • System Certification : ETAG

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

  • EWI (Woodfibre) accessories [EW01]

    Base plinth to exposed insulation edge.

    As EWI manufacturer

  • Woodfibre Insulation Between Floor Joists [FL01]

    Woodfibre Insulation.

    • Thickness 200mm.
    • Friction fit between joists to ensure air-tightness- cut batts approx 20mm wider than opening between joists.
    • Supported: Polyester webbing drawn underneath insulation at approx 600mm centres, fixed to joists.

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


  1. Admin - 2015-04-29 14:03:34 [Displayed version]

    Reference to "misapor" in technical description removed.

  2. Admin - 2015-04-29 14:01:53

    DWG file uploaded. FL01 and EW01 contact details amended to include Back to Earth contact information. General Formatting amendments.

  3. Admin - 2015-03-30 12:13:23

    Preview image updated.

  4. Admin - 2015-03-27 16:46:45

    Preview image and .pdf file updated.

  5. Admin - 2015-03-24 17:49:10

    General formatting. Approved doc links added in technical description; expanded with additional BS codes and notes. Parts list updated with suppliers links.

  6. Admin - 2015-03-24 17:48:47

    General formatting. Approved doc links added in technical description; expanded with additional BS codes and notes. Parts list updated with suppliers links.

  7. Admin - 2015-03-13 14:27:11

    Version 2. Title updated. Technical description updated and expanded. Parts list added.

  8. Admin - 2015-02-27 17:45:16

    Version 1

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