EWI to existing door with steps- threshold detail

Author details

Original Author:Admin Organisation:Retrofit Pattern Book

Detail summary

Detail of External wall insulation installed below an existing threshold to ground, or minimum 300mm below internal floor level. XPS insulation used to reduce thermal bypass and mitigate heat loss through the existing wall beneath the door threshold.

Where there are existing steps to threshold, these should be carefully removed to allow installation of external wall insulation and/or perimeter floor insulation followed by re-instatement or replacement as required.

Technical description

Section detail. External wall insulation to door threshold with steps. Where existing door to be retained in-situ.

Reference Specification:

For access and step heights: Please refer to Approved document M (access) for guidance.

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

For any new or existing brick/blockwork where not re-used: Aggregate concrete bricks and blocks: To BS EN 771-3. Autoclaved aerated concrete (AAC) blocks: To BS EN 771-4. Calcium silicate bricks: To BS EN 771-2. Clay blocks: To BS EN 771-1.

Cement: To BS EN 197-1 and CE marked.


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

  • External wall insulation for below ground [EW01a]

    Extruded Polystyrene (XPS) suitable for below ground conditions and for application of render.

    • Thickness: as EWI.
    • Depth: Minimum 300mm below internal floor level.
    • Thermal conductivity: 0.033W/m2k. GWP: <5.
    • Installation: Cut to fit around compact foam and steel supports to door threshold.
    • Joints: Tight butt joints

    BASF. Product Reference: Styrodur 2800C.

  • Structural Insulation beneath door threshold [FAB EW06a]

    Structurally improved Polystyrene insulation beneath door threshold

    • Thickness: as per drawing. Depth as per drawing.
    • Width: as per door threshold.
    • Thermal conductivity: 0.04W/m2k. GWP: <5.
    • Joints: tight butt joints

    Compacfoam. Product Reference: CompacFoam- 200

  • Concrete flag step [EW06b]

    Where difference between threshold and external ground level >200mm external intermediate steps of equal level should be provided.

    New steps should be constructed in masonry, using existing materials on site where possible. Steps should be even, with risers of 150mm minimum to 200mm maximum.

    Contractors choice.


  1. Admin - 2015-04-29 11:18:12 [Displayed version]

    DWG file uploaded.

  2. Admin - 2015-03-27 16:10:20

    Preview image and .pdf file updated.

  3. Admin - 2015-03-27 11:00:46

    Codes updated to match drawing.

  4. Admin - 2015-03-23 15:26:08

    Technical description reformatting.

  5. Admin - 2015-03-18 13:08:06

    Version 2- Introduction revised and expanded. Technical description re-written to include additonal detail, BS standards and code, Approved documents added. Parts list updated with codes and suppliers/manufacturers links.

  6. Admin - 2015-02-27 12:43:33

    Version 1

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