EWI stopping at internal corner

Author details

Original Author:Admin Organisation:Retrofit Pattern Book

Detail summary

Detail for woodfibre external wall insulation stopping at an internal against a perpendicular wall. corner.

Technical description

Plan detail. EWI to perpendicular wall, stopping at internal corner. Woodfibre external wall insulation system, with render stop and seal at junction point with existing perpendicular wall.

Suggested Installation sequence:

  1. Measure critical distances on site before ordering window/ door.
  2. Install door or window.
  3. Install external wall insulation.

Installation: by system manufacturer, or a contractor approved by the system manufacturer.

  • Weathertight under all anticipated conditions.
  • Capable of resisting all dead loads and design live loads, including impact and wind loads, and accommodating all thermal movements without damage.


Materials/ Surfaces: Do not use frozen materials and do not apply materials to frost bound surfaces.

Adhesives/ Mortars/ Renders: Do not apply when air temperature is at or below 5 °C on a falling thermometer or below 3 °C on a rising thermometer, or when temperature of the air or wall surface is above 30 °C and the surface is not protected. Temperature of the work: Maintained above minimum level recommended by manufacturer until adhesive/ mortar/ render has fully hardened.

Newly rendered surfaces: Protected against rain and snow by covering when precipitation occurs. Coatings damaged by rain or frost: Replace.


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/substrate: Before work- remove any existing loose material from external wall and prepare in accordance with manufacturer's requirements. Substrate to be structurally sound, adequately true and level, dry, free from contamination by dirt, dust, efflorescence or other deleterious substances, and in a suitable condition to receive specified coatings.

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

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.

Parts list

  • External Wall Insulation (Woodfibre), 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 (Woodfibre) accessories [EW01]

    Render stop to exposed insulation edge. Corner beading.

    Contacts: As EWI manufacturer.


  1. Admin - 2015-04-29 13:55:16 [Displayed version]

    DWG file uploaded. Formatting amendments.

  2. Admin - 2015-03-27 16:43:38

    Preview image and .pdf file updated.

  3. Admin - 2015-03-24 15:06:08

    General formatting. Technical description updated. Parts list suppliers links added.

  4. Admin - 2015-03-13 13:32:11

    Title updated. Technical reference updated. Parts list added.

  5. Admin - 2015-02-27 17:26:47

    Version 1

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