UK roofs present a range of challenges that mounting manufacturers must address: high wind speeds particularly in Scotland and coastal areas, a mix of concrete interlocking, clay plain, and slate tiles, and the increasing demand for aesthetically sensitive installations in conservation areas or on period properties.
MCS-certified installers must use mounting systems with appropriate test data for UK wind and snow loads. This is not a minor specification detail — incorrectly mounted panels can become a structural risk in storms and will void your roof guarantee with most building materials suppliers.
K2 Systems
K2 Systems is a German manufacturer with one of the largest installed bases among UK solar installers. Their modular rail-based systems accommodate virtually every roof tile type through an extensive range of compatible roof hooks.
K2 CrossRail for Pitched Roofs
The CrossRail system uses aluminium rails fixed to the roof structure via tile hooks, with panels clamped to the rails using mid and end clamps. Key features:
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- Compatible with concrete interlocking, clay plain tile, fibre cement slate, and natural slate
- Wind load calculations provided by K2's online planning tool (tested to BS EN 1991-1-4)
- 10-year product warranty on aluminium components
- Typical material cost: £400–£700 for a 12-panel system
- Black anodised finish available for enhanced aesthetics
K2 Flat Roof Solutions
For flat roofs (typically EPDM, felt, or GRP), K2 offers ballasted and mechanically fixed systems. The FlexRack system tilts panels at 10–15° to optimise output while minimising wind loading. Ballasted systems avoid roof penetrations, which is important for maintaining flat roof warranties.
Schletter
Schletter is another German market leader, well-regarded among UK commercial installers and increasingly popular for premium residential projects. Their FixGrid system is a distinctive cross-rail design that reduces the number of roof penetration points compared to parallel rail systems.
Schletter FixGrid for Pitched Roofs
- Cross-rail design with fewer roof hook fixings than parallel systems
- Particularly well-suited to fragile natural slate and clay plain tile roofs
- Integrated cable management channels within the rail profile
- Wind load tested to EN 1991-1-4; UK-specific calculation tool available
- Typical material cost: £500–£850 for a 12-panel system
- 30-year structural warranty on aluminium components
Schletter for Flat Roofs
Schletter's FlatFix Fusion system is designed for large flat roof commercial installations but is available for residential flat roofs. For smaller domestic flat roofs, installers often prefer simpler ballasted tilt-frame systems from specialist UK suppliers.
GSE In-Roof Integration
GSE In-Roof (Groupe Solaire d'Europe) is the most popular integrated mounting system in the UK — where the panels replace the roof tiles entirely rather than sitting on top of them. The result is a flush, flush appearance that is increasingly specified on new builds, planning-sensitive properties, and premium refurbishments.
How GSE In-Roof Works
- Existing tiles are removed from the installation area
- A GSE aluminium frame is fixed to the roof rafters
- Panels slide into the frame and are sealed with EPDM gaskets
- Adjacent tiles butt up to the frame perimeter
The system is waterproofed through the frame gaskets rather than conventional flashing, and the slimmer profile (panels sit within the tile plane rather than above it) reduces wind uplift compared to on-roof mounting.
GSE In-Roof Considerations
- Higher installation labour cost (typically £500–£1,200 more than on-roof)
- Reduced ventilation behind panels may marginally lower output in hot summer conditions (typically 1–3% loss)
- Excellent aesthetics — particularly valued in conservation areas and on Listed Building planning applications (though planning permission is still required for listed buildings)
- Compatible panel depth restrictions: panels must be 35–40mm thick; not all panel models are compatible
- 20-year product warranty
Mounting System Comparison
| Factor | K2 CrossRail | Schletter FixGrid | GSE In-Roof |
|---|---|---|---|
| Roof type | Pitched (all tile types) | Pitched (all tile types) | Pitched (tiles removed) |
| Aesthetics | Standard | Standard | Integrated / flush |
| Ventilation | Full | Full | Reduced |
| Wind load rating | High | High | Lower profile / better |
| Relative material cost | Low | Medium | High |
| Installation complexity | Standard | Standard | Higher |
| Best for | Budget-conscious installs | Fragile tile roofs | Planning-sensitive sites |
