EWI to top of monopitch, with small overhang over existing verge [Version ID #362]

Author details

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Detail summary

EWI detail for insulation running up to the top of an existing monopitch verge; forming a low parapet with stainless steel cap flashing. New lead flashing to junction of roof with insulation and stainless steel cap flashing over insulation and render. New EWI verge to side of parapet to aid water run-off.

Technical description

Section detail. EWI to monopitch verge to form parapet. New flashing and capping over EWI.

Suggested Installation Sequence:

  1. Fix new ply to existing fascia.
  2. Fix EWI, cutting back the flexible board to fit at top.
  3. Fix capping.

Reference Specification:

New flashing and membrane to BS EN 10088-2 and BS EN ISO 9445-1 or -2. with sealant to flashing to BS EN ISO 11600.

Natural slates to BS EN 12326-1 and -2. Battens, counterbattens and ridge/ hip fixing battens Timber species: To BS 5534, clause 4.12.1. Fasteners to BS 1202. All breathable membranes under Slating to be Agrément certified. Bitumen sheet to BS8747 Annex B.

Battens, counterbattens and ridge/ hip fixing battens Timber species: To BS 5534, clause 4.12.1. Fasteners to BS 1202. All breathable membranes under Slating to be Agrément certified. Bitumen sheet to BS8747 Annex B.

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.

Lead sheet: Rolled lead sheet to BS EN 12588. Tolerance (by weight): ±5%. Colour marked for thickness.

Soakers and step flashings (slate or tile roofs): Lead Soakers:

  • Length: Slate/tile gauge + lap + 25mm.
  • Upstand: 75mm (min)
  • Underlap: 100mm (min).


Lead step flashings:

  • Length: 1500mm (max).
  • End to end joint: laps 100mm (min).
  • Cover: overlap to soaker upstands 65mm (min) cover. Lead wedges at every course.
  • Fixing: lead wedges at every course.


Step and cover flashings (single lap tile roofs) in sheltered/ moderate exposure locations.

  • Length: 1500mm (max).
  • End to end joint: laps 100mm (min).
  • Upstands 85mm (min).
  • Fixing: Lead wedges at every course. Clipped at 500mm (max) centres along free edge.


Single step and cover flashings (single lap tile roofs) in exposed locations.

  • End to end joint: laps 50mm (min).
  • Cover: Overlap to soaker upstands 65mm (min) cover.
  • Fixing: Lead wedges at every step.


Lead cover flashings:

  • Length: 1500mm (max).
  • End to end joint: laps 100mm (min).
  • Upstands: 85mm (min).
  • Cover to roof: 150mm (min) and over first tile corrugation.
  • Fixing: turned over head of tiles. Clipped at first 500mm (max) centres along free edge. Upstand plugged and screwed to abutment in top third of each length only.

Notes

Care should be taken to ensure air-tightness. Seal all service penetrations. Lap and tape all membranes.

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: 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.

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) System With Rendered Finish [EW01]

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

    • Insulation back board: 100mm UdiTherm SK.
    • Insulation top board: 100mm 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. Product Reference: UdiFRONT.

  • Stainless Steel Flashings [RF09]

    To BS EN 10088-2 and BS EN ISO 9445-1 or -2. with sealant to flashing to BS EN ISO 11600.

    • Manufacturer: Contractor's Choice
    • Austenitic alloy grade 1.4301 (304).
    • Thickness: 0.4 mm.
    • Finish: Mill finished.
    • Minimum lap to roof covering: As drawing.
    • Fixing: Adhesive fix to membrane below.

    Contractor's choice

  • H71b Lead flashing [RF09]

    H71b lead sheet flashings and weathering. Rolled lead sheet to BS EN 12588.

    • Soakers: 1.50 to 1.75mm (code 3) lead sheet.
    • installation: Dressed over existing monopitch verge flashing, up and under stainless steel capping. (Refer to Lead Sheet Association LSA publication 'Rolled Lead Sheet: The Complete Manual'.

    Contractor's choice

Revisions

  1. Admin - 2015-05-01 09:23:51

    Title amended to match drawing.

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  2. Admin - 2015-04-29 15:07:49

    DWG file uploaded. General formatting amendments.

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  3. Admin - 2015-03-27 17:03:37

    Preview image and .pdf file updated.

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  4. Admin - 2015-03-24 18:10:37 [Displayed version]

    General formatting. Introduction expanded. Technical description approved doc links expanded. Notes added. Parts list updated with suppliers links.

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  5. Admin - 2015-03-24 18:10:04

    General formatting. Introduction expanded. Technical description approved doc links expanded. Notes added. Parts list updated with suppliers links.

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  6. Admin - 2015-03-13 16:00:22

    Technical description updated.Parts list updated.

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  7. Admin - 2015-03-06 13:52:10

    First version

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