EWI to Door Threshold

Author details

Original Author:Admin Organisation:Retrofit Pattern Book

Detail summary

Detail for external insulation below ground, where an existing door with step access is to be retained. Used where the existing internal floor void is inaccessible by usual means, and it is not possible to lift the whole internal floor. Use of a granular insulating infill below an existing concrete stone step increases the thermal efficiency of the building envelope, and reduces cold bridging through the existing door threshold.

Technical description

Section detail. External insulation below ground to wall with retained existing door. New concrete flag step and door step support to existing.

Reference Specification:

Please refer to Approved document M (access) for guidance on door thresholds and step heights from external ground level. Guidance on drainage below ground can be found in Approved documents C, section 3; and Document H, sections 2 and 3.

Perimeter insulation suitable for below ground use and drainage layer. To BS EN 13164

Blockwork: Aggregate concrete bricks and blocks: To BS EN 771-3. Autoclaved aerated concrete (AAC) blocks: To BS EN 771-4.


Granular insulation infill to minimum 300mm below level of internal floor finish to prevent thermal bridging.

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.

Parts list

  • Concrete Flag paving to form threshold step [FL03a]

    • Finish: Smooth.
    • Size: Size to suit step/threshold.
    • Colour: Natural/To suit existing (where present)
    • Jointing/bond: as per detail.

    Contractor's choice. Use reclaimed paving where possible.

  • Recycled plastic threshold support [FAB EW06b]

    Recycled plastic lumber.

    • Thickness: As detail.
    • Depth: as detail.
    • Width: as door threshold.

    British Plastics. Tel: 01422 88 57 61
    Web: http://www.britishrecycledplastic.co.uk/
    Product Reference: Recycled plastic lumber

  • Lightweight Aggregate Insulation bounding layer [FL03]

    Lightweight recycled glass aggregate.

    • Thermal conductivity: 0.08W/mk
    • Depth: As perimeter insulation. (min 200mm)
    • Width: 200mm.
    • Installation: Pour insulation in through the hatches and rake across the floor from above to achieve an even spread with minimum depth 200mm -taking care not to damage underfloor gas pipes and services. 50mm min. air gap to underside of joists. Ensure vents are not covered.
  • Blockwork Step support

    Used as shutter for grouted aggregate insulation, and to support flag step. Size: as required/as drawing. No: as required/as drawing.

    Contractor's choice.


  1. Admin - 2015-04-29 08:51:11 [Displayed version]

    Formatting amendments. DWG file uploaded.

  2. Admin - 2015-04-22 14:24:33

    Pdf detail file updated to include parts list codes.

  3. Admin - 2015-03-23 10:20:09

    Introduction revised to remove errors. Technical description updated with links to approved docs, parts list revised with links.

  4. Admin - 2015-03-13 17:52:00

    Technical description updated. Parts list revised.

  5. Admin - 2015-03-11 17:35:20

    Version 5. Parts listed updated with codes and additional parts information.

  6. Admin - 2015-03-11 16:54:18

    Version 4. Title update. Technical description updated and intro revised with additional detail. Preview image and pdf updated with new line type colours and lineweights.

  7. Admin - 2015-03-03 13:38:35

    Version 2. Parts list, title and description updated.

  8. Admin - 2015-02-27 12:12:05

    Version 2- .dwg file updated

  9. Admin - 2015-02-26 13:35:08

    First Version

Leave a comment


  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.

    User name

Leave a comment


A total of 14 users have left feedback about this detail.

Share your thoughts about this detail with other users:

Feedback summary

  • 80% of users found this detail easy to implement.
  • 50% of users found it easy to source skills for this detail.
  • 60% of users found this detail hard to understand.
  • 100% of users found the overall cost for this detail to be low.
  • 90% of users found materials for this detail easy to source.