EWI corner detail - change of material around corner [Version ID #187]

Author details

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Detail summary

Detail of corner junction between two types of external wall insulation system. Drawn for the junction of EPS and woodfibre insulation systems and appropriate seal detail at junction.

Technical description

Plan detail. EWI junction at external corner with perpendicular wall, EWI carrying round with change of material over corner. EPS insulation system junction with Woodfibre EWI insulation system. Adhesive to join insulation types with render carried round and over join; mastic seal to edge of join projecting beyond render to fully seal.

SUGGESTED INSTALLATION SEQUENCE: 1.) Fix EWI A to existing wall, edge hard up to corner, apply adhesive to exposed edge on corner. 3.) Fix EWI B to wall around corner, line edge up with face of Insulation A. 4.) Mastic seal to joint of insulation types. 5.) Corner reinforcement and render over.


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.

Expanded polystyrene (EPS): To BS EN 13163. Installed by system manufacturer/ contractor approved by manufacturer to weather-tight installation, to resist dead and live loads inc. impact and wind loads. Do not install in adverse weather conditions.

Parts list

  • Foam EWI System (140mm), rendered finish [FAB EW02a]

    Vapour permeable expanded polystyrene (EPS) external wall insulation: To BS EN 13163. \ Thermal conductivity: 0.031W/m2K. GWP: <5. \ Fixing: Adhesive bedding and mechanical fixing to substrate in accordance with manufacturer's recommendations. Adhesive: Baumit openContact - round perimeter of each board and three dabs within on each board. Fixing anchor: Baumit STR U. \ Reinforcement : Baumit openTex. \ Render system: Bsecoat : Baumit openContact. Primer: Baumit openPrimer. Topcoat: Baumit Nanopor Top. Beads/ Trims: Manufacturer's standard. Finish Colour: See schematic. \ System Guarantee: 25 years - ECO Compliant insurances and guarantees. System Certification: ETAG.

    Baumit \ www.baumitinsulation.co.uk \ Reference: Baumit EWI system: “Baumit open reflect - vapour permeable EPS”

  • External Wall Insulation (Woodfibre), rendered finish [EW01]

    For use on solid and hard to treat cavity walls. Composite woodfibre board. UdiTherm SK back board, Diffutherm NF (T&G, renderable) top board. \ Fixed mechanically to substrate in accordance with manufacturers recommendations. \ 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. \ Thermal conductivity: 0.045W/m2K. GWP 0.

    Unger \ www.unger-diffutherm.de \ Reference: UdiFRONT. \ Render: UDI Perl

  • Woodfibre EWI adhesive [EW01]

    Adhesive for use at joint between perimeter/ plinth insulation and external wall insulation.

    Unger \ www.unger-diffutherm.de \ Reference: Udi Dispersion Adhesive


  1. Admin - 2015-04-29 13:23:03

    Intro summary updated. Parts list contact details amended for EW01. DWG uploaded.

  2. Admin - 2015-03-27 16:36:41

    Preview image and .pdf file updated.

  3. Admin - 2015-03-24 15:17:42

    Errors in parts list removed.

  4. Admin - 2015-03-24 14:43:45

    General reformatting. Technical description updated with additional clauses.

  5. Admin - 2015-03-24 13:26:33

    General reformatting. Introduction revised. Technical description expanded with additional clauses. Parts list updated with suppliers links. EWI accessories added.

  6. Admin - 2015-03-24 13:26:02

    General reformatting. Introduction revised. Technical description expanded with additional clauses. Parts list updated with suppliers links. EWI accessories added.

  7. Admin - 2015-03-13 12:54:15 [Displayed version]

    Title update. Intro and technical description expanded and updated. Parts list added.

  8. Admin - 2015-02-27 16:57:38

    Version 1

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