Roofing Inspection

Roof load-bearing structures must be designed and constructed in accordance with DIN EN 1995-1-1 (Eurocode 5 for timber structures) or the applicable material Eurocode, with national application via the German National Annex. Timber roof structures must additionally comply with DIN 1052 for traditional detailing conventions. All structural members must be correctly sized for the design loads including self-weight, imposed loads, snow loads (DIN EN 1991-1-3 with NA), and wind loads (DIN EN 1991-1-4 with NA). Timber must be strength-graded in accordance with DIN 4074 and bear the appropriate grade stamp. Connections must use approved fasteners and be executed per the structural engineer's design. Structural timber must be protected from moisture during construction and achieve a moisture content below 20% at the time of enclosure.

1. Verify member sizes and spans against the approved structural drawings and static calculation

2. Check timber grading marks — confirm strength class (e.g. C24) per DIN 4074 on each member

3. Inspect connections — correct fastener types, quantities and spacings per the structural design

4. Measure timber moisture content with a pin-type meter — must be below 20% before enclosure

5. Confirm bracing and stability elements are installed as shown on the structural drawings

6. Check bearing points for correct support conditions and adequate bearing length

- Timber members installed with moisture content exceeding 20%, risking shrinkage and fungal decay

- Connections with missing or incorrect fasteners compared to the structural design specification

- Bracing elements omitted or incorrectly positioned, compromising lateral stability

- Notches or holes cut into structural members without engineering approval, reducing load capacity

Roof underlayment and vapor control layers must be designed and installed in accordance with DIN 4108-3 (moisture protection) and the ZVDH (Zentralverband des Deutschen Dachdeckerhandwerks) technical rules. The underlayment beneath pitched roof coverings must be a water-resistant, vapor-permeable membrane classified per DIN EN 13859-1, with laps and connections sealed in accordance with ZVDH guidelines. A vapor barrier or vapor retarder must be installed on the warm side of the insulation, with its sd-value selected based on a moisture calculation per DIN 4108-3 or a Glaser calculation to prevent interstitial condensation. Membrane overlaps must achieve the minimum widths specified by the manufacturer and the ZVDH — typically 100 mm horizontal and 150 mm vertical. All penetrations and connections to adjacent construction must be sealed airtight.

1. Verify the underlayment membrane classification and sd-value match the specification and DIN 4108-3 requirements

2. Check lap widths — minimum 100 mm horizontal and 150 mm vertical as per ZVDH and manufacturer requirements

3. Inspect lap sealing — tapes or adhesive applied to clean, dry surfaces with full adhesion and no wrinkles

4. Confirm the vapor barrier is positioned on the warm side of the insulation with no interruptions

5. Check sealing at penetrations (pipes, cables, rooflights) — airtight connections with appropriate grommets or tapes

- Vapor barrier positioned on the wrong side of the insulation or interrupted by penetrations without sealing

- Underlayment membrane laps not properly sealed, allowing wind-driven rain to penetrate

- Sd-value of vapor control layer not matched to the roof build-up, causing interstitial condensation risk

- Membrane damaged during subsequent trades (e.g. tile battens nailed without self-sealing capability)

Pitched roof coverings must be installed in accordance with the ZVDH Fachregeln (technical rules) for the specific covering type. Concrete roof tiles must comply with DIN EN 490 and clay roof tiles with DIN EN 1304. Slates must meet DIN EN 12326. The minimum roof pitch for the selected covering type must be observed as defined in the ZVDH rules — if the actual pitch falls below the standard minimum, additional measures (enhanced underlayment, reduced lap reduction) are required per the ZVDH Regeldachneigung tables. Tile and slate fixing must follow the ZVDH wind load calculation based on DIN EN 1991-1-4 with the German National Annex, ensuring adequate mechanical fixing in edge, corner and field zones. Ridge, hip and verge details must be executed per ZVDH standard details.

1. Confirm roof pitch meets or exceeds the ZVDH minimum for the selected covering type — verify additional measures if below standard pitch

2. Check tile or slate product markings for compliance with DIN EN 490, EN 1304 or EN 12326 as applicable

3. Inspect mechanical fixing — verify clip or screw fixing pattern matches the ZVDH wind load zone calculation for edge, corner and field areas

4. Check headlap dimensions against ZVDH requirements for the given roof pitch

5. Inspect ridge, hip and verge details for compliance with ZVDH standard details and correct mortar or dry-fix installation

- Roof pitch below the ZVDH minimum without the required additional underlayment measures

- Insufficient mechanical fixing of tiles in exposed edge and corner zones per the wind load calculation

- Headlap reduced below the ZVDH minimum for the actual roof pitch, risking water ingress

- Ridge and hip tiles poorly bedded or dry-fix systems incorrectly installed, allowing wind uplift

Flat roof waterproofing must be designed and installed in accordance with DIN 18531 (waterproofing of roofs and balconies). The waterproofing classification must match the usage category (K1 for non-utilized or K2 for utilized roofs) and the design life requirement. Minimum waterproofing thickness and number of layers must comply with DIN 18531-2 for the selected material system — bituminous membranes, synthetic single-ply membranes (PVC, TPO, EPDM) or liquid-applied systems. The roof must achieve a minimum fall of 2% (1.2 degrees) toward drainage points as recommended by DIN 18531. All upstands must extend a minimum of 150 mm above the finished roof surface or above the maximum expected water level. Joints, overlaps and connections must be executed per manufacturer specifications and DIN 18531-3 installation rules.

1. Verify the waterproofing system classification meets the DIN 18531 category (K1 or K2) for the intended roof use

2. Measure falls to drainage points — minimum 2% gradient, check for ponding areas or backfalls

3. Check upstand heights at parapets, walls and penetrations — minimum 150 mm above finished surface level

4. Inspect membrane joints and overlaps — correct overlap width, full adhesion or welding without wrinkles

5. Verify detail execution at corners, outlets and penetrations per DIN 18531-3 and manufacturer guidelines

- Insufficient falls resulting in ponding water that accelerates membrane degradation

- Upstand heights below 150 mm at parapets or door thresholds, creating water ingress risk

- Membrane lap joints incompletely welded or bonded, providing a path for water penetration

- Penetration flashings not properly integrated with the membrane system, causing localized leaks

- Root protection layer missing on green roof areas, allowing plant roots to damage the membrane

Roof flashings and penetration details must be executed in accordance with ZVDH technical rules for pitched roofs and DIN 18531 for flat roofs. All junctions between the roof covering and abutting walls, chimneys, dormers, roof windows and service penetrations must be weatherproofed with appropriate flashing systems. Metal flashings must be formed from materials suitable for the application — typically zinc (DIN EN 988), aluminum, copper or stainless steel — with adequate allowance for thermal movement. Lead flashings, where used, must comply with DIN EN 12588. On pitched roofs, stepped and cover flashings at abutments must be dressed into mortar joints or chase-cut grooves and sealed. Pipe penetrations must use proprietary roof penetration collars or custom-fabricated flashings that integrate with the underlayment and outer covering systems.

1. Inspect all wall abutment flashings — verify correct step and cover flashing installation with adequate chase depth and sealant

2. Check chimney flashings for continuous weathertight detail on all four sides including the back gutter

3. Verify roof penetration collars are correctly sized, sealed to the pipe and integrated with both the underlayment and the outer covering

4. Inspect metal flashing material and gauge — confirm suitability and compliance with the relevant DIN EN standard

5. Check for thermal movement allowance in long flashing runs — expansion joints at recommended intervals

- Stepped flashings not properly chased into masonry or sealed, allowing wind-driven rain penetration

- Chimney back gutters undersized or poorly formed, causing water to back up behind the chimney

- Penetration collars not properly sealed to the pipe surface, especially on corrugated or profiled coverings

- Dissimilar metals in contact causing galvanic corrosion — e.g. copper flashings on zinc gutters without isolation

Roof drainage systems must be designed in accordance with DIN EN 12056-3 (gravity roof drainage) and DIN 1986-100 (drainage systems on private ground). Gutter and downpipe sizing must be calculated based on the effective roof area and the local rainfall intensity (r5,5 value from KOSTRA-DWD 2020 data for the site location). Gutters must be installed with a minimum fall of 0.5% toward the outlets. Overflow provisions are required per DIN 1986-100 for flat roofs — emergency overflow scuppers or secondary drainage outlets must be sized to handle the century rainfall event (r5,100). Materials must be suitable for the application and compatible with the roof covering and facade materials. Rainwater downpipes must connect to the site drainage system or rainwater harvesting system as specified in the drainage design.

1. Verify gutter and downpipe sizing calculations against the effective roof area and KOSTRA rainfall intensity for the location

2. Check gutter gradient — minimum 0.5% fall toward outlets, no backfalls or ponding sections

3. Inspect overflow provision on flat roofs — emergency overflows correctly positioned and sized per DIN 1986-100

4. Confirm downpipe connections to the below-ground drainage system or rainwater harvesting tank

5. Check material compatibility — no galvanic corrosion risk between gutter, fixing and facade materials

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

- Missing or undersized emergency overflow provision on flat roofs, risking structural overloading

- Gutter installed without adequate fall, leading to standing water, debris accumulation and accelerated corrosion

- Downpipes not connected to the drainage system, discharging water against the building foundation