EWI to Existing Parapet Eaves

Author details

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Detail summary

A detail for external wall insulation, designed to deal with potential cold bridge at eaves; where new or existing loft or roof insulation meets external wall insulation. Where there is a limited overhang at the existing eaves, an integral gutter is required to enable water run-off. Here the EWI is brought up to form a verge, which is then capped with stainless steel flashing and associated gutter.

Technical description

Section detail. EWI to existing wall. Up to existing overhanging eaves, with loft insulation joined to EWI.


  1. Carefully remove minimum 750mm of tiles or slates, putting to one side for reuse. Note positions of existing roofing battens. Remove roofing battens to at least 600mm up the roof from the existing eaves.
  2. Roll back existing loft insulation to reveal junction between ceiling and roof. Remove any debris. Ensure gap between rafters is clear to either eaves board or 200mm beyond outer edge of wall (where no eaves board), whichever is the smaller.
  3. Glue battens to upper surface of the eaves insulation boards 100mm in from each edge. On leading edge of the slab taper batten thickness to minimise risk of obstruction on installation.
  4. Once glue has set, push slabs into the gap over the top of the sole plate up to the eaves board or 200mm past, whichever is the smaller. Fix Eaves board over top of existing parapet eaves to EWI.
  5. Fix external wall insulation (FAB EW01) to form new parapet.
  6. Install breathable membrane/ roof underlay [RF06c] approx 500mm up roof slope from front edge of EWI. Pin in place to rafters with galvanised clouts at upper edge. Dress over EWI outer layer so as not to protrude beyond the front face.
  7. Insert stainless steel gutter system over the top of the breather membrane/ roof underlay and EWI as shown on drawing. Fix in place with self drilling fixings to every third rafter at inner upper edge.
  8. Roll original membrane back over new stainless gutter to lap new gutter by 200mm. If required replace roofing battens in original locations up to approx 600mm above bottom edge of gutter. Dress the existing membrane over this reinstalled batten. Insert last batten at approx 350mm up from the edge of the gutter.
  9. Roll the original membrane over the top of the polycarbonate vent strip.
  10. Replace slates/tiles, dressing last slate/tile so as to be just below the upper edge of the gutter.
  11. Install loft insulation (FAB RF01) - making sure it meets the back of the eaves insulation (FAB RF06c)

Reference Specification:

All guttering to BS EN 12056-3, clauses 3–7 and National Annexes. Collection and distribution of rainwater: Complete, and without leakage or noise nuisance.

Tiling work: Clay tiles to BS EN 1304/ concrete (non interlocking) to BS EN 490. All battens/counterbattens and ridge/hip fixing battens to be timber species to BS 5534, Clause 4.12.1. All fasteners to BS 1202 as appropriate to fastener type.

For all works to existing roofs refer to Approved document C (resistance to contaminants and moisture), with reference to Section 2, and section 6.

Reference should be made to Document H (drainage and waste disposal). Approved Document F (ventilation) should be referred to with regards to ventilation to existing roofs and over eaves ventilation. Document L1b should be referred when working on existing dwellings, with particular attention to sections 5 and 6 regarding material alterations. Document L2b should be referred to with existing buildings other than dwellings.


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

  • Insulation to Eaves (rigid) [RF06c]

    • Manufacturer: Contractor's choice.
    • Phenolic foam.
    • Size: 50mm thickness
    • Width: cut to suit rafters.
    • Length: 750mm PLUS distance to eaves board or 200mm (whichever smallest).
    • Thermal conductivity: 0.023W/m2k.
    • Installation: Continuous with roof insulation, no gaps, to avoid cold bridging. Friction fit between rafters from inside loft, being careful not to damage existing roof membrane or structure or block existing ventilation paths.

    Contractor's choice

  • Breathable Membrane [RF06c]

    Roof underlay. Sealed to phenolic foam insulation and dressed to drainage point at the end of each run of guttering to allow water to exit construction.

    Green Building Store. Tel: 01484 461705. Email: info@greenbuilding store. Web: http://www.greenbuildingstore.co.uk
    Product Reference: Solitex Plus

  • Stainless Steel Gutter system [RF06c]

    Flashing at junction between flat roof verge and external wall insulation. To BS 460, and BS EN 12056-3, clauses 3–7 and National Annexes.

    • Manufacturer: Contractor's choice.
    • Profile: As drawing.
    • Gauge: 1.2mm min.
    • Jointing: Joints to be avoided where possible. If required must be fully welded and tested. Could be glued and blind riveted subject to approval.
    • Size: Contractor's choice- to suit existing roof dimensions and cover depth of external wall insulation. Ensure provides adequate capacity for rainwater discharge from roof.
    • Finish as delivered: Self finished Stainless Steel grade 304.
    • Setting out: To falls.
    • Fasteners: as manufacturers recommendations.
    • Accessories: As welded stop ends.
    • Testing: Test on completion.

    Contractor's choice

  • Breathable membrane to loft insulation [FL01]

    Breathable membrane/ wind-tight layer.

    • sd value : 0.01m
    • Installation: Laid over top of loft insulation to prevent thermal bypass - joints to be lapped and taped.

    DuPont Tyvek. Web: http://tyvek.co.uk/Tyvek_EMEA_Landing/en_GB/index.html
    Product Reference: Tyvek Housewrap

  • Loose laid loft insulation [FAB L01a]

    Flexible formaldehyde free glass mineral wool. Should be laid continuous to eaves: level, covering all parts of the ceiling to meet any eaves/ internal wall insulation to prevent cold bridge. All service holes sealed, debris removed before laying insulation. Eaves ventilation should be unobstructed. Any electric cables overlaid by insulation should be sized accordingly. Where water cistern platforms located on ceiling joists: Insulation below omitted.

    • Recycled content: 85% (minimum) to BS EN ISO 14021.
    • Thermal Conductivity: 0.040 W/mK. GWP 0.
    • Thickness to 400mm

    Knauf Reference: Knauf Earthwool loft roll 40

  • Double/Single-sided air seal tape [DP09b/a]

    Tape for junctions critical to air-tightness.

    • Location: see detail drawings - generally critical junctions for air-tightness. Size: 60mm (Single sided)/ 85mm (double sided).
    • Accessories: ORCON F sealant and TESCON PRIMER RP (for use on rough/old surfaces to assist adhesion)

    Back to Earth: Tel: 01392 861763. Web: http://www.backtoearth.co.uk/
    Product reference: TESCON VANA/ TESCON PROFIL - 2 release tapes (single sided) \ Contega SL (double sided)

  • 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

    Product Reference: UdiFRONT.

  • Sealing to ceiling edges [DP03]

    • Location: all ceilings.
    • Description: Seal all ceilings and repair any cracks in plastre to ensure no air leaks.
    • Product: Standard decorators caulk

    Contractor's choice.


  1. Admin - 2015-03-27 16:21:59 [Displayed version]

    Preview image and .pdf file updated.

  2. Admin - 2015-03-27 12:26:20

    Woodfibre EWI added to parts list. Air sealing to ceiling added to parts list. codes amended to match drawing.

  3. Admin - 2015-03-23 15:02:08

    General formatting. Technical description updated and installation sequence revised. Parts list updated with codes and suppliers links.

  4. Admin - 2015-03-12 15:58:51

    Intro and technical description updated and expanded. BS and Approved doc information added. Parts list added.

  5. Admin - 2015-03-03 15:12:57

    Preview image updated. Parts list added.

  6. Admin - 2015-02-26 15:36:58

    First Version

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