System Types
Cantilever Canopies: Single-Post Solar Structures
Cantilever canopies use a single column on one side of the car bay, with the structure cantilevering over the vehicles. No column in the middle of the bay — maximising access and enabling higher clear heights for ambulances and HGVs. Below: full spec, cost by size, foundations and a worked payback.
Get a cantilever designIn short: Cantilever canopies put the column on one side only — unobstructed bays, 4.0–5.5m clear heights — at £1,150–£1,600/kWp, about 20–35% over mono-pitch; the only design for ambulance and accessible bays.
What Is a Cantilever Solar Canopy?
A cantilever canopy places its structural columns on one side of the bay only (usually the rear boundary of the car park or the wall of an adjacent building). The canopy structure then extends horizontally over the parking spaces without any column in the bay itself.
This creates a completely unobstructed bay — no column to drive around, no central post to restrict door opening, no obstruction for tall vehicles. The trade-off is a more structurally demanding design: the cantilevering moment requires larger column sections and deeper foundations.
Key Advantages of Cantilever Design
Unobstructed access: No columns within the bay. Essential for:
- Hospital A&E drop-off zones (ambulance access)
- Disabled/accessible parking bays (wheelchair transfer needs clear space)
- Loading bays requiring forklift access
- Luxury car parks where door-ding risk must be minimised
Higher clear heights: Because columns are at the perimeter, the underside of the canopy can be raised to 4.0-5.5m clear height without structural compromise — allowing ambulances, fire appliances, and HGV cabs to pass beneath.
Bifacial panel advantage: With no structure beneath the panels (other than the perimeter column), bifacial solar panels can capture reflected light from the ground surface below. On light-coloured tarmac or concrete, bifacial gain of 8-15% versus monofacial is achievable.
Structural Design
Cantilever canopies carry significantly higher structural loads than mono-pitch or T-frame alternatives. Our standard specification:
| Element | Specification |
|---|---|
| Columns | 250x250 or 300x300 CHS, wall thickness 10-16mm, hot-dip galvanised |
| Foundation | Bored in-situ pile, 600-900mm diameter, 6-9m depth (site-specific) |
| Cantilever arm | Fabricated welded steel assembly, structural S355 or S460 |
| Purlins | Aluminium extruded or galvanised steel, designed for combined wind uplift and panel load |
| Panel attachment | Stainless mid-clamp and end-clamp, tested to EN 61215 mechanical load spec |
| Cantilever span | 3.5-5.5m from column face (vehicle bay depth) |
| Column spacing | 5.5-6.5m along bay length |
| Clear height | 3.5m minimum, up to 5.5m on request |
Foundation Depth and Ground Investigation
Because cantilever foundations carry both vertical load and a significant bending moment (from the wind and snow loading on the cantilevering structure), they require more substantial foundations than standard canopy types. A geotechnical investigation is essential before detailed design. Typical foundation:
- 600mm bored pile, 7m deep: for soft clay with N-value 10-20
- 450mm bored pile, 5m deep: for firm to stiff clay with N-value 20-40
- Ground screw (where applicable): suitable on dense cohesive soils, avoids excavation
We commission a site investigation report (preferably Phase 2 geotechnical with CPT or trial pits) as part of the detailed design process for all cantilever projects.
Cantilever Canopy Cost by Size
Cantilever canopies cost approximately 20-35% more per kWp than mono-pitch due to the higher structural cost per bay — indicatively £1,150–£1,600 per kWp installed:
| System size | Approx. bays | Indicative installed cost | Annual generation |
|---|---|---|---|
| 50 kWp | 14–16 bays | £62,000–£80,000 | ~47,500 kWh |
| 100 kWp | 28–32 bays | £130,000–£180,000 | ~95,000 kWh |
| 250 kWp | 70–80 bays | £300,000–£400,000 | ~237,500 kWh |
| 500 kWp | 140–160 bays | £575,000–£760,000 | ~475,000 kWh |
Bifacial gain partly offsets the premium: with unobstructed sky view from below, a cantilever array typically yields 98–102% of an equivalent mono-pitch despite the structural cost. A 100 kWp cantilever saving ~£20,000/yr at current commercial rates pays back in 6.5–9 years, or faster with the 100% Annual Investment Allowance applied. See the full solar canopy cost guide.
However, for applications where access is paramount (NHS, ambulance zones, MSCP perimeter), there is no alternative — the cantilever is the only design that meets the access requirement. For standard car parks where access is not constrained, a mono-pitch canopy or T-frame canopy will typically be more cost-effective.
Applications
- NHS hospital drop-off zones: Ambulance access height, unobstructed bay access
- Accessible parking: Unobstructed bay allows full door opening and wheelchair transfer
- Luxury car parks (hotels, premium retail): No door-ding risk
- Loading areas: Forklift access beneath canopy
- Multi-storey car park roofs: Cantilever from parapet wall avoids roof penetrations
Get a Cantilever Feasibility Study
We assess whether a cantilever is the right structural choice for your site or whether a mono-pitch or T-frame would be more cost-effective. Free desk-based feasibility within 5 working days includes structural scheme recommendation, access height assessment, PVSyst yield model, and 25-year DCF.