EWI Recessed Plinth to just below ground

Author details

Original Author:Admin Organisation:Retrofit Pattern Book

Detail summary

Detail for external wall insulation plinth to ground, where the internal floor of the building to be retrofitted is solid beneath the internal finished floor level. EWI is carried down to 300mm minimum below internal floor level to prevent cold bridging, but stopped short of external ground level.

Technical description

Section detail. EWI Perimeter insulation to below internal floor level. Stopping before external ground level.


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 Services/openings

Gas Meters and Inlets: Gas meters and inlets 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.

Soil Pipes: An assessment of the condition of soil pipes should be undertaken prior to external wall insulation being undertaken. Assume soil pipes will remain in situ unless agreed in by contract administrator. However in some cases pipes may need to be replaced/ moved. Any changes to existing pipework to be agreed in writing by the contract administrator before work starts.

Rainwater Pipes and Waste Water Drainage: Rainwater pipes and waste water pipes will be moved to the outer face of insulation as standard, and swan-necked back into gulleys where possible. Any work additional to this should be agreed in writing with the contract administrator.

Windows and doors: Where windows and doors are to be replaced in insulation please refer to contract/window schedules for details. Where windows and doors are to be retained in insulation please refer to relevant detail drawings to show reveal insulation and cills.

Parts list

  • EWI(Woodfibre), with rendered finish [EW01]

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

    • Insulation back board: UdiTherm SK.
    • Insulation top board: 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 accessories [EW01]

    Base plinth for render edging over.

    As per EWI manufacturer.


  1. Admin - 2015-05-01 08:52:22 [Displayed version]

    DWG and PDF file drawing file title updated to match title on site, and to avoid duplicate information.

  2. Admin - 2015-04-29 11:40:10

    EW01 parts list updated. DWG uploaded.

  3. Admin - 2015-03-27 16:27:53

    Preview image and .pdf file updated.

  4. Admin - 2015-03-27 12:57:40

    Base plinth added to parts list

  5. Admin - 2015-03-23 16:58:09

    General re-formatting. Parts list updated to latest revision.

  6. Admin - 2015-03-23 16:56:35

    General re-formatting. Parts list updated to latest revision.

  7. Admin - 2015-03-12 17:09:27

    Version 2- Parts list updated. Technical description expanded.

  8. Admin - 2015-02-27 15:29:27

    Version 1

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