Solar Mounting Systems

What the mounting system is

Everything between the roof structure and the panel. On a pitched roof that means a set of anchors fixed into the rafters, aluminium rails spanning between them, and clamps holding the panel frames to the rails. It is unglamorous hardware and it decides more about the long-term outcome than the panel choice does.

Two jobs. It has to carry the load — the weight of the array plus whatever the wind does to it — into the structure. And it has to leave the roof as watertight as it found it.

How the load path works

An array is light in itself. What matters is wind. A panel above a roof surface is a flat plate in an airstream, and the uplift force on it in a gale far exceeds its weight. That force goes through the clamps into the rails, through the rails into the anchors, and through the anchors into the rafters.

Every element in that chain has to be sized for the site: how exposed it is, how high the roof is, how close the array sits to the ridge and the verges where pressures are highest. Positions near an edge see much greater uplift than the middle of a slope, which is why arrays are set back from edges and why anchor spacing is often closer at the perimeter.

This is a calculation, done for the specific property. It is not a matter of putting a hook every metre because that is what was done last time.

Fixings go into rafters

This deserves stating plainly because it is where most poor installations fail. The anchor bolts into a rafter or another structural member. It does not bolt into a batten, which is a thin timber intended to hold tiles and nothing else, and it is not fixed to the covering.

Rafter spacing on older houses is frequently irregular, and the array layout has to be set out against what is actually there rather than an assumed centre. This is one of the reasons a physical survey with loft access matters more than an aerial measurement.

Covering types

Concrete and interlocking clay tiles. A tile hook passes under the tile above and bolts to the rafter. The tile beneath is relieved so it sits flat rather than rocking on the hook.

Slate. Brittle and unforgiving. Hooks and fixings for slate differ, and the number of slates disturbed has to be minimised because a cracked slate is a leak. Slower work, and priced accordingly.

Metal and profile roofs. Clamps that grip the standing seam without penetrating, where the profile allows, or purpose-made fixings into the structure where it does not.

Flat roofs. Ballasted frames sitting on protection mats spread the load without piercing the membrane, which is the preferred approach where the structure will take the weight. Where it will not, mechanically fixed frames are used and every penetration is detailed and sealed by a roofer.

In-roof. The covering under the array is removed and a proprietary tray or flashing system takes its place, with the panels forming the weathering layer.

Suitability and structural limits

Not every roof will take an array. Long-span rafters at wide centres, previous alterations, cut roofs on older properties and known spread are all reasons to bring in a structural assessment before designing a layout. A flat roof carrying ballast almost always needs one.

Installation implications

The mounting sets the programme. It goes on first, it needs scaffolding, and the roof is open at the fixing points while the work proceeds — so weather matters. Earthing continuity between rails and frames is part of the installation, not an afterthought.

Warranty and cost

Mounting manufacturers warrant their systems on the condition that they are installed to the published method, with their own components. Mixing parts between systems voids that.

On cost, mounting is a modest proportion of the quotation on a straightforward tile roof and a significant one on slate, in-roof or flat-roof work, where labour and additional materials rise sharply. Your quotation identifies the specific system and method for your covering.