Mounting solar panels on an Onduline roof

Fixings and rails

• Onduline: Hanger bolt M10×200 into the rafter → rafters. The sheet is not load-bearing, penetrations may void the Onduline warranty. Do not overtighten — you will dent the corrugation.
• Combustible roof covering. Running external wiring above combustible roofs is prohibited (НАПБ А.01.001-2014, sect. IV ch. 1 cl. 1.18): route DC cables in metal trays or conduits, not on the roof covering; penetrations made of non-combustible materials. Check the roof covering’s combustibility group against the certificate (ДБН В.1.1-7:2016 Annex A).

Check before installation

• The sheet manufacturer’s warranty terms: what they say about penetrations.
• Where the rafters run. The fixing goes into the rafter only; the sheet holds nothing.
• The roof covering’s fire class. It decides how cables may run over the roof.

Calculation for three cities

A typical 12 × 7 m slope at 30°, rafters every 600 mm, 20 panels of 2,350 × 1,100 mm in 2 rows. Snow and wind under DBN V.1.2-2:2006 for the regional centre; a 6 m high house.

Uplift and pressure are the design forces on one fixing next to the typical capacity the calculation assumes. An array near the eaves or the gable lies in the wind edge zone, where the calculation places fixings closer together.

In all three cities the typical roof passes with the fixing spacing the calculation chose.

Drawings

Bill of materials for the typical roof (Kyiv)

20 panels, 11.00 kW. Quantities from the calculation for Kyiv; open the constructor for your own roof.

Installation step by step

The Solispec engine writes the steps for the typical roof in Kyiv: rafter numbers, marking out and quantities come from the same calculation. Steps that depend on the roof covering are given in full, those shared by all pitched roofs in short.

1. Roof inspection: from the attic, check the rafters (section ≥ 50×150 mm, no rot or cracks, spacing ~600 mm) and the condition of the roof covering.
2. Mark out the 11 180 × 4 720 mm array: 1 190 mm from the eaves, 410 mm from the left gable.
3. Fixings: on rafters №2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 drill the sheet at the corrugation crest Ø12, pilot Ø7 into the rafter. Hanger bolt M10×200 (72 pcs) ≥ 70 mm into the rafter, EPDM + sealant. Do not overtighten, so as not to crush the corrugation.
4. Rails: fix the rails to the brackets with T-bolt M8 (1 per fixing, 72 pcs), adjusting the bracket height so that the rails are in one plane.
5. Earth the array: bond the rails of each row to each other and to the rails of other rows with a 6 mm² Cu conductor via rail earthing clamps.
6. Make the cable penetration through the roof covering above the array: a penetration with an EPDM collar or a cable gland, sealant under the flashing.
7. Install the panels from bottom to top, starting from the gable.
8. Fix the cables to the frames and rails with stainless steel clips every 300–400 mm so that they do not lie on the roof covering or rub against its edge.
9. Install snow guards above the eaves below the array across the full width of 11 180 mm, fixed into the rafters.
10. Check the penetrations after the first rain (from the attic — for any traces of water).

The shared steps in full are on the section page

Common mistakes

• Over-tightening the hanger bolt. The sheet is soft and the corrugation gets crushed.
• Drilling in the trough. Drill only on the crest, with an EPDM washer and sealant.
• Running DC cables over the roof covering. The roof is combustible: cables in metal trays or conduit.