Mounting solar panels on a flat roof: ballast and frames

How much ballast: three supports, three cities

One row of 5 panels at 15°, two supports per line, middle of the roof, a 6 m high building. Each cell shows the row’s ballast and how much is needed against wind uplift alone under DBN V.1.2-2:2006. «Passes» means every check passed: uplift, sliding, overturning and supports.

Light lintels are heavy enough against uplift but fail on sliding and stability where the wind is stronger. The calculation takes a reference friction between support and roof covering — confirm it for your roof.

A row on «Бордюр дорожній БР 100.30.15 · 108 kg» supports in Kyiv

• Ballast 1 296 kg ≥ 290 kg against uplift (ДБН В.1.2-2:2006 as amended by No. 1 (2007) and No. 2 (2020): wind 286 Pa × c_f 1.10). Sliding: ≈ 589 kg needed (μ = 0.40, PVC/TPO + rubber mat — for reference, confirm by measurement).
• Roof load-bearing capacity not checked. The array imposes ≈ 290 kg/m² (ultimate, with snow), under a support ≈ 1 051 kg/m². Enter the permitted load from the survey or the roof slab design (“Permitted roof load” field).

Bill of materials for the typical roof (Kyiv)

5 panels, 2.75 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 row in Kyiv: part marks, quantities and tightening torques come from the same calculation.

1. Prepare the parts in the workshop: cut and drill per the “Parts” section (К1, О1, С1, С1а, С2, Х1, Р1), holes Ø11. Deburr, paint cut edges and holes with zinc paint, write its mark on each part with a marker. Close the tube ends with 42×42 end caps, drill a Ø6 drain hole at the lowest point of each part. Check: the number of parts of each mark matches the bill of materials.
2. Mark out the row: length 5 720 mm, 6 trusses at 1 040 mm spacing, end ones — 260 mm from the rail ends. Node points A (front) and B (rear) — 1 980 mm apart. Check: diagonals of the rectangle between the end trusses 5 564 mm each, difference ≤ 10 mm.
3. Place 10 mm rubber mats (12 pcs) under every support: the mat projects beyond the support by ≥ 50 mm and does not cover drains or membrane seams. Check: every support sits fully on its mat; check the roof load against the “Roof” section of the calculation.
4. Install the supports: 12 × BR 100.30.15 along the row. Level the top with a level or string line. Check: all supports in one plane ±5 mm, in line ±10 mm.
5. Assemble 6 trusses on a level area: О1 + С1 at node B (via a spacer insert, one bolt M10×150), К1 to О1 (node A) and to С1 (node C), then С2. Bolts M10×110 grade 8.8 — 2 per node (36 in total), washers under the head and nut, spring washer under the nut. Tighten “hand-tight” only. Check: top chord angle 15.0° ±0.5° (inclinometer), trusses identical when stacked on top of each other.
6. Node M: the top chord and the inner strut lie in planes one profile apart — between them a spacer insert cut from the same profile, bolt M10×150 through both profiles and the insert. Node B: the rear post sits on the other side of the top chord — back to back with the base, also via a spacer insert and bolt M10×150.
7. Place the trusses on the supports at the marked points, О1 along a string line. Fix to the supports with chemical anchors: threaded rod M10×165 grade 5.8 (24 pcs), hole Ø12 90 mm deep exactly on the support axis, ≥ 50 mm from the edge; clean: 2× blow-out + 2× brush + 2× blow-out, resin from the bottom to 2/3; load only after curing per the datasheet (+20 °C ~1 h, +5 °C up to 6 h), washer 40×40×4, 20 N·m. Check: С1 plumb (spirit level, ±2 mm over the height), spacing 1 040 ±5 mm, diagonals 5 564 mm.
8. Braces Х1 between rear posts С1 (cross in the end bays (4 pcs)): bolts M10×110, 1 per end. Before tightening, plumb the posts once more.
9. Lay rails Р1 on top chords К1 at 420, 1 730 mm from lower node A (holes already made), overhang 260 mm on each side. Every rail/top chord crossing — bolt M10×110 (12 in total).
10. Align and tighten: stretch a string line along the top of each rail — deviation ≤ 3 mm over the panel length and ≤ 5 mm per row, rails parallel. Then tighten all M10 with a torque wrench: 25–30 N·m (tube — do not crush), spring washer fully compressed. Check: spot-check 10% of the bolts, re-measure the diagonals 5 564 mm.
11. Earth the frame: to the first and last truss of each row — PV-3 flexible wire 6 mm² (green-yellow) via a cable lug under bolt M8 with a serrated washer on an area cleaned of paint. Bond the rows together, run the wire to the building's earthing system / MET (if there is lightning protection — per the design, with separation distance). Check: test the continuity of the protective conductors and the connection to the MET with an instrument (resistance — per the electrical design).
12. Install the panels from bottom to top, starting from one end of the row. End clamps for 35 mm frames (4 pcs) — on the first and last panel, ≥ 20 mm from the rail end. Mid clamps (8 pcs) — between panels, gap 20 mm. Bolt M8×100 A2 through the rail with self-locking nut DIN 985 and a wide washer underneath (12 pcs). Rails must be at 520 mm from the short panel ends — check against the clamping zone in the datasheet. Tighten to 14–16 N·m. Check: the panel does not move, the clamps are not skewed.
13. Fix the panel cables to the rails and frames with stainless steel clips or UV-resistant black cable ties every 300–400 mm. MC4 connectors do not lie on the roof covering or the ground and do not hang loose; there is a drip loop. Earth the module frames: an earthing clip under each mid clamp or a cable lug in the frame's ⏚ hole.
14. Re-tighten all bolts after 2–4 weeks and after the first strong wind: M10 — 25–30 N·m (tube — do not crush), clamps — 14–16 N·m. Check that the ballast and mats have not shifted and that there are no scratches on the galvanising (touch up). Then — inspect yearly.

Common mistakes

• Counting uplift only. The calculation also checks sliding and overturning — in the table above they are what fails the light lintels.
• Setting supports straight on the membrane. A rubber mat goes under every support, clear of drains and seams.
• Not knowing the roof slab’s capacity. Enter the allowed load from a survey or the design — the calculation compares it with ballast and snow.