PV roof mounting: the components explained
A PV roof mounting kit is built from aluminium rails, mid and end clamps that hold the modules, and a roof anchor sized to the roof type: a roof hook for tiles or a hanger bolt for trapezoidal sheet, all tied together with T-bolts and sliding nuts. The aluminium is EN AW-6060 T6 and the roof anchors that carry the load are stainless, so the whole assembly resists corrosion for the twenty-five-year-plus life of the array. This guide explains each component, how the parts fit the roof covering, and how many fixings a module needs. For the full system see our guide to PV mounting systems.
What a roof mounting kit has to do
The mounting kit has one structural job: to transfer the weight of the modules, and the wind and snow loads on them, into the roof structure without leaking and without corroding. It does this through a chain of parts, from the module clamp down to the roof anchor and into a rafter. Every link in that chain has to carry the load and survive the weather, which is why the metals and the fixings are chosen with care rather than left to chance. ULAMEX supplies the mounting components, not the modules or the electrical parts.
Mounting rails
The rails are the backbone of the system. They run across the roof, fixed to the roof anchors, and the modules clamp onto them, so the load from every module is spread into the anchors and down into the roof. ULAMEX rails are extruded from EN AW-6060 T6 aluminium, a corrosion-resistant architectural alloy with a proof strength around 150 MPa, and the PV profile is a 40 x 40 mm section with a hex channel sized for M8 and M10 bolts. The rail is supplied in a range of lengths so a run can be built up to suit the array, and rails are spliced with connectors where a row is longer than a single length.
Mid clamps and end clamps
The clamps hold the modules to the rails. A mid clamp sits between two neighbouring modules and grips the frame of both at once, while an end clamp secures the last module in a row. Both are aluminium, matched to the rail, and are made in a range of heights, typically 30 to 50 mm, to fit the frame thickness of standard modules, including the 400 W, 500 W and larger bifacial panels now common. The clamp is tightened to a set torque onto the module frame, which both holds the module and, on many systems, bonds it electrically to the rail for earthing.
Roof hooks for tiled roofs
On a pitched tiled roof the rail is carried on roof hooks, which are stainless steel brackets that reach under a tile, screw to the rafter or a batten, and bring a fixing point out above the tile for the rail. The hook is shaped to the tile profile, so there are different hooks for a concrete interlocking tile such as the Frankfurter Pfanne, for a plain clay tile such as the Biberschwanz, for an S-tile, and for slate. ULAMEX makes the load-bearing roof handles from stainless V2A (1.4301), because a hook takes the full pull-out load of the array in a wind gust and must never corrode where it sits hidden under the tile.
Hanger bolts for trapezoidal and standing-seam roofs
A metal roof needs a different anchor. On trapezoidal steel sheet and similar profiled roofs the rail is fixed with a hanger bolt, a double-threaded stud that screws into the roof structure at one end and takes a nut and the rail bracket at the other, sealed with a bonded washer so the penetration stays watertight. Standing-seam roofs can often be clamped without any penetration at all, using a seam clamp that grips the fold. Choosing the anchor to match the roof covering, and sealing every penetration, is what keeps a mounted array both secure and leak-free.
Flat roofs: ballast and triangles
A flat roof is usually not drilled at all. Instead the modules sit on triangular support frames that set the tilt angle, and the whole assembly is held down by ballast rather than by fixings into the roof, which protects the waterproof membrane. The ballast is arranged to resist wind uplift across the array, in south-facing or east-west layouts, and ULAMEX supplies ballast in aluminium and in Magnelis-coated galvanised steel, in Z-type and standard forms. This non-invasive approach suits commercial flat roofs where the membrane must stay intact. For the zinc-magnesium coating see our guide to galvanised steel and DX51D.
Bolts, nuts and connecting hardware
The small parts tie the system together. T-bolts drop into the rail channel and lock with a quarter turn, sliding nuts let a fixing be positioned anywhere along the rail, and connectors splice two rails into a continuous run. Hanger bolts, sliding nuts, end caps and earthing hardware complete the kit. Every fastener that sits in the weather is stainless, so it does not rust and does not set up a galvanic cell against the aluminium rail. Matching the fastener grade to the exposure, A2 inland and A4 near the coast, is a small detail that protects the whole array.
Earthing and bonding
A mounted array has to be electrically bonded so that every metal part sits at the same potential and any fault current has a safe path. The mounting system carries earthing components for this, from bonding clips that bite through the anodised layer to make a connection, to lugs that take an earthing conductor. The structural bonding is part of the mounting kit; the electrical connection and the earthing design itself belong to the installing electrician. Getting the bond right also stops stray currents from driving corrosion at the joints over the life of the array.
How many fixings per module
The number of clamps and roof anchors is a structural question, not a guess. As a rule of thumb a module is held at four points in a standard wind zone, and up to six where the wind or snow load is high, but the exact figure comes from the wind and snow calculation for the site to the Eurocode, EN 1991. A roof on an exposed coast or in a mountain snow region needs more anchors and a stronger rail than a sheltered inland roof. Sizing the fixings to the real load, before installation, is what keeps the array on the roof through a storm.
Why the metals matter
A rooftop array is fixed for a quarter of a century in all weather, so the corrosion behaviour of every part decides how long it lasts. Aluminium forms a self-healing oxide and does not rust, which is why the rails and clamps are EN AW-6060 T6. Stainless is used for the roof hooks and fasteners that take the load, because those parts must not fail hidden under a tile. Galvanised steel with a Magnelis coating gives long life on ballast. Keeping to these metals, and never mixing a bare carbon-steel part into a wet joint, is what lets the mounting outlast several changes of inverter. For the aluminium side see our guide to whether aluminium corrodes.
Cable management
The direct-current cabling between the modules and down to the inverter has to be held clear of the roof and out of standing water, so cable management is part of the mounting kit. Cable clips and clamps fix into the rail channel and route the cables along the rail, off the roof surface, while edge protection stops a sharp rail edge chafing the insulation. Keeping the cables clipped up, rather than lying on the tiles, protects them from ultraviolet light, abrasion and pooling water and keeps the array tidy for inspection. On a metal roof the cables are kept off the hot sheet for the same reason, and every clip is a small part that adds years to the cabling.
Matching the kit to the module and roof
A mounting kit is specified to two things: the module and the roof. The clamp height is chosen to the frame thickness of the modules, the rail length and count to the array size and layout, and the roof anchor to the exact covering, whether that is a concrete tile, a plain clay tile, slate or trapezoidal sheet. The pitch of the roof and its rafter spacing decide where the anchors land, and the wind and snow zone sets how many are needed. Because these vary from roof to roof, ULAMEX quotes the kit against the roof type, the module and the site rather than from a fixed bill of materials, so the parts that arrive fit the job.
PV mounting components from ULAMEX
ULAMEX manufactures PV mounting components under EN 1090 and has supplied the trade since 1988.
| Component | Detail |
|---|---|
| Rails | EN AW-6060 T6 aluminium, PV profile 40 x 40 mm, hex channel for M8 and M10 |
| Clamps | Aluminium mid and end clamps, 30 to 50 mm to fit standard and bifacial frames |
| Roof hooks | Stainless V2A (1.4301) for concrete tile, plain tile, S-tile and slate |
| Metal roofs | Hanger bolts with bonded washers; seam clamps for standing-seam |
| Flat roofs | Triangle supports with aluminium or Magnelis ballast, Z-type and standard |
| Hardware | T-bolts, sliding nuts, connectors, end caps, earthing components |
Planning a PV project? Send the roof type, module count and site, and ULAMEX will return a non-binding quotation with lead time and availability. Browse the photovoltaic mounting range, read the full PV mounting systems guide, or view our supply capabilities. Contact the export desk at [email protected] or +48 504 424 761.
Frequently asked questions
What are the main parts of a PV roof mounting kit?
Aluminium rails run across the roof and the modules clamp onto them with mid and end clamps. The rails are carried by a roof anchor matched to the covering: a stainless roof hook for tiles or a hanger bolt for trapezoidal sheet. T-bolts, sliding nuts, connectors and earthing hardware tie it together. ULAMEX supplies these components, not the modules or electrics.
What aluminium is used for PV rails?
EN AW-6060 T6, a corrosion-resistant architectural alloy with a proof strength around 150 MPa. The ULAMEX PV profile is a 40 x 40 mm section with a hex channel sized for M8 and M10 bolts, supplied in a range of lengths and spliced with connectors for longer rows. Aluminium does not rust, so the rail lasts the life of the array.
What roof hook do I need for my roof?
The hook is matched to the tile profile. There are different stainless hooks for a concrete interlocking tile such as the Frankfurter Pfanne, a plain clay tile such as the Biberschwanz, an S-tile and slate. On trapezoidal steel sheet a hanger bolt with a bonded washer is used instead, and a standing-seam roof can often be clamped without any penetration.
How are modules fixed on a flat roof?
Usually without drilling. The modules sit on triangular support frames that set the tilt, and the assembly is held by ballast rather than fixings, so the waterproof membrane stays intact. ULAMEX supplies ballast in aluminium and Magnelis-coated galvanised steel, in Z-type and standard forms, in south-facing or east-west layouts.
How many fixings does each module need?
As a rule of thumb a module is held at four points in a standard wind zone, and up to six where the wind or snow load is high. The exact number comes from the wind and snow calculation for the site to the Eurocode, EN 1991. Exposed coastal and mountain sites need more anchors and a stronger rail.
Does ULAMEX supply the solar panels too?
No. ULAMEX supplies the mounting system: the aluminium rails and clamps, the stainless roof hooks and hanger bolts, the ballast and the fasteners, all under EN 1090. The modules, inverters and electrical work are handled by the installer. Send the roof type and module count and the export desk will quote the mounting components.