Accessories for Roofs
Accessories for Roofs are the small parts that turn a rail kit into a finished, watertight installation: roof hooks and hanger bolts, EPDM sealing washers, flashings and collars, end and mid clamps, rail joiners, earthing clips, cable entry glands and roof cable trays. Choose them by covering, by module frame height and by fastener grade, A2 stainless inland and A4 in coastal or industrial air. They complete every pitched roof and rail profile layout. Guide
Related accessory categories
- Rail profiles
- Shingle roof fixings
- Trapezoidal roof fixings
- Seam clamps for folded metal
- Electrical installation material
What is in a roof accessories order
A mounting order splits into four groups. Fixings get the load into the building: adjustable roof hooks for tile, hanger bolts for boarded decks, self-drilling screws for sheet. Sealing parts keep water out at those points: bonded EPDM washers, flashings and membrane collars. Rail hardware makes the array one structure: end and mid clamps matched to frame height, rail joiners and expansion splices, T-bolts and channel nuts. Electrical parts finish it: earthing clips, cable entry glands and cable trays. Fastener grade runs through all of it: A2 stainless inland, A4 with added molybdenum in coastal and industrial air.
FROM THE FIELD
"The parts that hold up a job are never the rails, they are the twenty-cent items. A van short of end clamps in the right frame height stops an array at ninety percent complete. I order clamps by measured frame height, not by module name, and I carry spare EPDM washers: one driven and backed off is scrap."
Ladislav Proc · Mounting systems specialist, ONSA Plus
How to choose roof mounting accessories
Work from the roof outwards. The covering decides the fixing and its seal, the module frame decides the clamps, rail length decides the joiners, and the environment decides the stainless grade. Get those four right and the parts list follows.
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Matching the fixing and seal to the covering
Each covering has one correct fixing family and one correct way of sealing it, and mixing them is the commonest cause of a leak.
- Adjustable roof hooks: stainless brackets for clay and concrete tile, adjustable in two or three axes so the arm clears the tile without bearing on it. The rafter takes the load.
- Hanger bolts: double-threaded studs, wood thread into the rafter and metric thread to the rail foot, for boarded decks under shingle or felt. Supplied with a bonded EPDM washer that is compressed once, to torque, and never reused.
- Flashings and collars: a metal flashing slides under the shingle course above the fixing, a membrane collar is welded into felt. Both give a mechanical water path, not just an elastomer.
- End and mid clamps: selected by measured frame height, commonly 30 to 40 mm. End clamps carry the outer edge, so an undersized one is what lets a module lift.
- Rail joiners: a plain splice for short runs, a sliding expansion splice on long ones, since aluminium moves roughly 23 µm per metre per kelvin and a rigid run bows against its fixings.
Earthing, cable entry and cable routing
Anodised aluminium is a surface insulator, so a bolted rail joint is not a reliable bonding path. Where bonding of the array frame is required, use toothed earthing clips or jumpers that cut through the anodic layer, terminated with an outdoor rated lug. Where the DC cabling leaves the roof, use a cable entry gland with an IP66 body and a drip loop before it, never a hole and sealant. Along the roof, DC cable belongs in a cable tray or UV-stable clips on the rail, never on the covering.
Tip from practice
Watch what touches what. Aluminium rail against copper flashing, or a bare steel screw through an aluminium foot, sets up a galvanic cell that a wet roof runs free of charge. Keep A2 or A4 stainless with aluminium and use an isolating pad wherever the alloys differ.
Stainless grades: A2 or A4
Both are austenitic stainless and look identical on the shelf, so the grade is specified before delivery, not chosen on the roof. A2 is chromium nickel and suits inland roofs in normal atmospheres. A4 adds molybdenum, which is what resists chlorides, so it belongs within a few kilometres of the coast, near industrial exhaust, around pools and where de-icing salt reaches the roof. Both pair safely with aluminium rail.
Frequently asked questions about roof accessories
What is the difference between a roof hook and a hanger bolt?
A roof hook is an adjustable stainless bracket that reaches over a tile and bolts to the rafter, so the covering carries no load. A hanger bolt is a double-threaded stud driven through a boarded deck into the rafter and sealed with an EPDM washer.
How do I choose the right module clamps?
By measured module frame height, commonly 30 to 40 mm, and by position: mid clamps between two modules, end clamps at the row ends. They must sit inside the clamping zone the module manual specifies.
Should I use A2 or A4 stainless fasteners?
A2 is the default for inland roofs in normal atmospheres. A4 contains molybdenum and resists chlorides far better, so specify it near the coast, around swimming pools and where de-icing salt is in the air.
Can an EPDM sealing washer be reused?
No. The elastomer is compressed once to a specified torque and takes a permanent set. A washer driven and then backed off no longer seals, and neither does the hole it came out of. Fit a new fastener in fresh material.
Do aluminium rails need separate earthing clips?
Where bonding of the array frame is required, yes. The anodic layer on aluminium is an insulator, so a bolted rail joint is not a dependable conductor. Use toothed bonding clips or jumpers that cut through to clean metal.
How should DC cable be routed on the roof?
In a cable tray or UV-stable clips fixed to the rail, never loose on the covering where grit abrades the insulation. Where it leaves the roof, use an IP66 rated gland with a drip loop before it, not a hole sealed with mastic.
Fixings and sealing components must suit the specific covering, the structure below it and the fastener grade required at the site.
About ONSA Plus
Why installers across Europe order roof accessories from us
ONSA Plus is a European B2B distributor of photovoltaics, battery storage, heat pumps and EV charging stations. In our own EU warehouses we keep over 1,500 products from 25+ brands, including Huawei, Solis, SolaX and Dyness.
We are not just a trading company. We design and service energy systems ourselves, so we answer questions on roof fixings, sealing and earthing from engineering practice, not from a catalogue. You handle a warranty claim directly with us and you buy per job.
