Roofing Systems

Per EN 1991-1-1, permanent loads (self-weight of roofing, battens, insulation) must be accurately determined. Snow loads must be calculated per EN 1991-1-3 using the characteristic ground snow load for the site location and roof shape coefficients. Wind loads per EN 1991-1-4 must account for uplift on the roof covering, including higher local pressures at edges and corners. The structure must be designed to Eurocodes EN 1993 (steel), EN 1995 (timber), or EN 1992 (concrete).

1. Verify roof structure design has been checked for the combination of dead, snow, and wind loads per Eurocodes

2. Confirm timber sizes, grades, and spacing match the structural engineer's specification per EN 1995-1-1

3. Check truss or rafter connections — nail plates, hangers, straps — are installed per design details

4. Inspect bracing layout matches structural drawings (diagonal bracing, binders)

5. Verify roof structure members are free from damage, excessive notching, or unauthorised modifications

- Bracing omitted or incomplete, leading to instability under wind load

- Truss nail plates not fully embedded due to poor pressing during manufacture

- Timber members notched or drilled for services without structural engineer approval

- Snow load not correctly assessed for the site altitude and roof geometry

Per EN 13859-1, underlays for discontinuous roofing (tiles, slates) must meet declared performance characteristics for water penetration resistance, tensile strength, and UV resistance during exposure. Vapour control layers per EN 13984 must be installed on the warm side of the insulation in cold roof constructions to prevent interstitial condensation. Laps and junctions must be sealed per manufacturer's requirements.

1. Verify underlay product carries CE marking per EN 13859-1 with declared performance values

2. Check underlay is correctly draped with minimum 10 mm sag between rafters to allow drainage

3. Confirm lap widths meet manufacturer's requirements (typically 100–150 mm horizontal, 150 mm vertical)

4. Verify vapour control layer is installed on the warm side of insulation per EN 13984 where required

5. Inspect sealing of vapour control layer at all penetrations, laps, and perimeter details

- Underlay installed too taut, preventing water drainage to eaves

- Horizontal laps insufficient, allowing wind-driven rain to bypass the underlay

- Vapour control layer punctured by services or fixings without being sealed

- Vapour control layer omitted in cold roof construction, leading to interstitial condensation

- UV-degraded underlay due to prolonged exposure before roof covering installed

Concrete tiles must comply with EN 490 and clay tiles with EN 1304, each with CE marking and declared frost resistance. Bitumen shingles must meet EN 544. Tiles must be fixed according to the manufacturer's fixing specification, which accounts for roof pitch, site exposure, and tile type. Minimum headlap and sidelap requirements vary by tile profile and roof pitch. Battens must be treated softwood graded to appropriate standards.

1. Verify tile or covering product carries CE marking per EN 490, EN 1304, or EN 544

2. Check batten gauge (spacing) matches the tile manufacturer's requirement for the specific roof pitch

3. Confirm fixing pattern complies with manufacturer's specification for the site wind exposure zone

4. Verify headlap and sidelap dimensions meet minimum requirements for the roof pitch

5. Inspect ridge, hip, and valley details for correct installation with mechanical fixings

- Batten gauge incorrect, resulting in reduced headlap and risk of water ingress

- Insufficient tile fixings for the wind exposure zone, leading to uplift risk

- Ridge and hip tiles bedded in mortar only without mechanical fixings

- Valley tiles cut too short, reducing the effective gutter width

- Battens not treated or of incorrect cross-section for the rafter span

Reinforced bitumen sheet membranes must comply with EN 13707, with declared values for tensile strength, tear resistance, and flexibility at low temperature. Single-ply plastic and rubber sheet membranes must meet EN 13956. Where green roofs are installed, root resistance must be verified per EN 13948. Minimum falls of 1:40 (designed) to achieve 1:80 (as built) are recommended to prevent ponding.

1. Verify membrane product carries CE marking per EN 13707 or EN 13956 as applicable

2. Check membrane is fully bonded, mechanically fixed, or ballasted as specified by the design

3. Confirm laps meet manufacturer's minimum width (typically 75–100 mm) and are correctly welded or bonded

4. Verify falls are adequate to drain water to outlets without ponding (minimum 1:80 as built)

5. Inspect membrane at all penetrations, upstands, and perimeter details for continuity

- Ponding due to insufficient falls or deflection of the roof deck under load

- Membrane laps poorly welded or bonded, creating water ingress paths

- Upstand heights insufficient (minimum 150 mm above finished roof level recommended)

- Membrane punctured by foot traffic or subsequent trades without repair

Metal flashings for roofing must comply with EN 14782 (self-supporting) or EN 14783 (fully supported). Flashings at abutments must be stepped or continuously dressed into the wall construction with a minimum upstand of 75 mm above the roof covering. All penetrations (pipes, vents, rooflights) must be detailed with proprietary or site-formed flashings to maintain weathertightness. Materials must be compatible to avoid bimetallic corrosion.

1. Verify flashing materials comply with EN 14782 or EN 14783 and are compatible with adjacent materials

2. Check abutment flashings are correctly stepped into or chased into mortar joints with minimum 75 mm upstand

3. Inspect penetration flashings for continuity and secure fixing around pipes, vents, and rooflights

4. Confirm edge trims and verge details are mechanically fixed and weathertight

5. Verify expansion joints are provided in long runs of metal flashings per manufacturer's guidance

- Abutment flashings with insufficient upstand, allowing wind-driven rain behind the flashing

- Bimetallic corrosion where incompatible metals are in contact (e.g. aluminium and copper)

- Penetration flashings not dressed tightly to pipe, leaving gaps for water entry

- Lead flashings not properly bossed or welded at corners, creating wrinkles that hold water

Roof drainage design must comply with EN 12056-3 for gravity systems, considering rainfall intensity for the building location. Half-round gutters must meet EN 607 and eaves gutters and fittings per EN 612. Gutter sizing must accommodate the effective roof area, with outlets positioned to limit flow length. Downpipes must discharge to a suitable drainage system and be securely fixed to the building.

1. Verify gutter size is adequate for the effective roof area per EN 12056-3 calculations

2. Check gutter falls are adequate (minimum 1:350 recommended) towards outlets

3. Confirm gutter brackets are spaced per manufacturer's requirements (typically 600–900 mm centres)

4. Verify downpipe connections are secure and discharge to the below-ground drainage system

5. Inspect leaf guards or balloon gratings at outlets where trees are in proximity

- Gutters undersized for the effective roof area, causing overflow in heavy rainfall

- Insufficient gutter fall resulting in standing water and silt accumulation

- Gutter joints leaking due to failed sealant or incorrectly assembled fittings

- Downpipes discharging onto the ground surface instead of connecting to the drainage system

- Snow guards not installed where required, allowing snow slides to damage gutters