Structural loading capacity
Modern warehouse buildings (post-2010) are typically designed with sufficient structural loading reserve to accept ballasted PV systems (15-20 kg/sqm typical) without structural reinforcement. Older buildings (pre-2000) sometimes require structural assessment and occasional reinforcement, particularly where the roof was originally designed only for snow load and live load without renewable retrofit allowance. Our standard structural survey produces a Building Engineer's report for each install — the loading reserve is the key output.
Roof material assessment
Modern profiled steel roofs (Kingspan, Tata, Corus) accept both ballasted and mechanically fixed PV systems and are typically the optimum substrate. Membrane roofs (single-ply, EPDM, modified bitumen) accept ballasted-only systems and require careful UV protection. Asbestos cement roofs (pre-2000) cannot be retrofitted — combined re-roof + PV is the only viable path and adds £150-500k to project capex. Mansard or pitched roofs require different mounting systems and longer install programmes.
Sprinkler and fire suppression clearances
LPC sprinkler clearance standards mandate 1m clear to deflector and 0.6m at high-bay spray heads. PV layout must respect these clearances. Sometimes existing sprinkler heads need relocation to achieve target system size — adds £2-15k to project capex. Insurer pre-design review is mandatory for buildings above 5 MW capacity or where consequential loss exposure is high (cold chain, food production, pharmaceutical).
Electrical infrastructure
Modern warehouses typically have 800A or 1200A three-phase supplies that absorb significant PV without main switchboard upgrades. Older buildings may require switchboard modifications (£15-50k) or new dedicated PV switchboards. Power factor correction is sometimes needed where existing motors have poor PF.
DNO grid connection capacity
G99 grid connection is the rate-limiting step on most warehouse PV projects. We submit G99 immediately after structural survey to start the clock. For systems above 1 MW, expect a G99 study to take 65-90 working days followed by 6-14 months for connection on capacity-constrained networks. Some sites have unconstrained capacity (rare); some have severe constraints requiring expensive grid reinforcement (rare).
Common questions
What's the maximum PV system size for a typical warehouse roof?
Modern logistics buildings of 200,000-800,000 sqft can accommodate 1-5 MW of rooftop PV. Smaller industrial units of 30,000-80,000 sqft typically take 200-600 kW. The binding constraint is rarely roof area — usually DNO capacity, structural loading, or sprinkler clearance reduces the achievable system size.
Can asbestos cement roofs be retrofitted with solar?
No. Asbestos cement roofs cannot be retrofitted with rooftop PV — neither structurally nor health-and-safety wise. The right path is combined re-roof + PV, replacing the asbestos roof with profiled steel and installing PV on the new roof. The PV business case sometimes pays for the re-roof over project lifetime; always flagged in the proposal.
How much does a structural survey cost?
£3-8k for typical warehouse, £8-25k for older heritage or unusual structures. Mandatory before mounting design. Included as standard project deliverable in our scope.