The short answer
Solar panels are fixed to a typical UK pitched roof using a mounting system that anchors into the roof timbers, not the tiles. Installers lift a tile or slate, bolt a roof hook (or bracket) to the rafter or batten beneath, and refit the tile over it. Aluminium rails are then attached across the hooks, and the panels are secured to those rails with clamps. This is the common on-roof method, where panels sit a few centimetres above the tiles. An alternative is in-roof mounting, where panels replace the tiles and sit flush within the roof surface. Either way, the load is carried by the roof structure, and flashing or weatherproof seals keep the roof watertight. Done correctly, the fixings hold the array securely against UK wind for the system's life.
Panels need to stay put through decades of British weather, so how they attach to the roof matters. This page explains the fixing method step by step and how the roof stays watertight.
Key facts
- Anchored intoRoof timbers (rafters/battens), not tiles
- Holds the panelsRoof hooks, rails and clamps
- On-roof mountingPanels sit above the tiles
- In-roof mountingPanels replace tiles, sit flush
- WeatherproofingFlashing and seals keep roof watertight
The on-roof fixing method, step by step
Most UK domestic installations use the on-roof method, which works with existing tiles or slates. The sequence is broadly:
- Locate the rafters. The installer finds the roof timbers, because the fixings must anchor into structural wood, not just the tile.
- Fit roof hooks. A tile is lifted and a roof hook (or bracket) is bolted to the rafter or batten beneath, then the tile is refitted over it, sometimes trimmed slightly to sit flat.
- Mount the rails. Aluminium mounting rails are bolted across the protruding hooks, forming a level framework above the roof.
- Clamp the panels. Panels are lifted onto the rails and held with clamps — mid-clamps between panels and end-clamps at the edges.
- Wire and earth. The panels are connected together and the metalwork is earthed for safety.
The result is an array sitting a few centimetres above the tiles, with air able to circulate underneath — which helps keep the panels cool and slightly more efficient.
Each of these steps is governed by the mounting manufacturer's instructions and the array's structural design, so the spacing of the hooks and rails is not arbitrary. The hooks are positioned to spread the load across enough rafters to carry the weight of the panels and to resist the wind trying to lift the array, and the clamps are torqued to set figures. This is why a well-installed array looks tidy and evenly spaced: the geometry is dictated by the engineering, not just the appearance.
On-roof vs in-roof mounting
The two mounting approaches suit different situations:
- On-roof is the standard, lower-cost option. Panels sit on rails above the existing tiles. It is quicker to fit, works on most roofs, and leaves the original roof covering intact.
- In-roof (integrated) mounting sets the panels into the roof in place of the tiles, so they sit flush with the surface for a sleeker look. It is popular on new builds and re-roofs and is sometimes preferred for appearance or in conservation-sensitive settings, but it costs more and is more involved to fit.
Both are secure and weatherproof when installed properly. The choice usually comes down to appearance, cost and whether the roof is being recovered anyway — fitting in-roof panels during a re-roof avoids doubling up on labour.
| Aspect | On-roof | In-roof |
|---|---|---|
| Position | Above the tiles | Flush, replacing tiles |
| Appearance | Slightly raised | Sleeker, integrated |
| Relative cost | Lower | Higher |
| Best suited to | Most existing roofs | New builds / re-roofs |
| Panel cooling | Good (airflow beneath) | Less airflow beneath |
Comparison for guidance only. Source: Energy Saving Trust.
Keeping the roof watertight and sound
A common concern is whether drilling and lifting tiles risks leaks. A competent installation keeps the roof watertight because the fixings are designed for the job: roof hooks are shaped to let the tile sit back down over them, and any penetration is sealed or flashed. In-roof systems use purpose-made flashing kits to channel water around the panel array.
The roof structure also has to bear the extra weight of the panels and mounting, which is modest for a typical array but should be checked by the installer, especially on older or unusual roofs. A pre-installation survey assesses the roof's condition and load capacity. If the roof covering is near the end of its life, it is often sensible to recover it before fitting panels, since removing and refitting an array later adds cost. Installed correctly by an MCS-certified installer, the fixings hold the panels securely against UK wind loads and the roof remains weatherproof for the life of the system.
Different roof coverings and structures
The exact fixing hardware varies with the roof covering, and a competent installer matches the method to your roof:
- Concrete or clay tiles — the most common UK pitched roof. Roof hooks are fitted to the battens or rafters and the tile is refitted over the hook, sometimes trimmed slightly to sit flat.
- Slate — more brittle, so installers use slate-specific hooks or hangers designed to avoid cracking the slates while anchoring securely to the structure.
- Metal or profiled sheet roofs — use clamps or brackets suited to the profile, often without penetrating the sheet.
- Flat roofs — panels sit on tilted frames, either anchored down or held by ballast (weights), set at an angle to catch the sun since the roof itself is level.
Whatever the covering, the principles are the same: the load is carried by the building's structure, penetrations are weatherproofed, and the array is fixed firmly enough to resist wind uplift. The survey establishes the roof type, its condition and its load capacity before any design is finalised, which is why two homes can end up with visibly different mounting hardware. On unusual or older roofs the installer may bring in a structural check. The takeaway is that solar mounting is a well-established trade with proven methods for every common UK roof, and a properly certified installer will choose and fit the right system so the panels stay secure and the roof stays sound for decades.
Frequently asked questions
Will fixing solar panels damage my roof or cause leaks?
A competent installation should not. Roof hooks are designed so the tile sits back over them, and any penetration is sealed or flashed to stay watertight. The installer should survey the roof first to check its condition and that it can bear the load. Using an MCS-certified installer reduces the risk of poor workmanship.
Are the panels bolted to the tiles or the roof structure?
To the structure. The mounting hooks or brackets bolt onto the rafters or battens beneath the tiles, so the roof timbers carry the load. The tiles are lifted to fit the hooks and then refitted over them. Fixing to the tiles alone would not be strong enough to resist UK wind.
What if my roof needs replacing soon?
It is usually best to recover the roof before fitting panels, because removing and refitting an array later adds cost and disruption. If you are re-roofing anyway, in-roof (integrated) panels can be fitted at the same time. An installer's survey will flag whether the existing covering has enough life left.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific home. They are guidance, not a quotation or guaranteed saving.