Farm solar and roof replacement timing

For UK farms with older buildings, the question of when to do solar PV typically intersects with the question of when to replace the roof. Getting the timing right delivers both energy generation and modernised buildings as a single coordinated investment. Here’s the 2026 framework.

Two timing scenarios

Scenario 1: Roof has substantial remaining life (15+ years). Modern profiled steel cladding installed post-2000 typically has 30-40 years of remaining life. PV can be installed directly with no re-roof. The PV system’s 25-year operational life sits well within the remaining building life.

Decision: install PV now. Don’t wait for roof replacement that’s still 15+ years away. PV economic case stands alone.

Scenario 2: Roof is past nominal life or has asbestos cement. Pre-2000 buildings with asbestos cement cladding cannot accept PV directly. Other buildings with deteriorated cladding (visible damage, missing fixings, weather penetration) need replacement before PV.

Decision: combined re-roof + PV. The PV business case routinely pays for 60-100% of the re-roof over the 25-year system life. The re-roof was needed anyway; PV makes the combined project economic.

How to assess remaining roof life

For each building, evaluate:

Cladding age. Buildings constructed post-2010: 20+ years of remaining nominal life. 2000-2010: 15-20 years. 1990-2000: 0-15 years remaining nominal life (likely past nominal). Pre-1990: past nominal life, often asbestos cement.

Visible condition. Look for: surface weathering (Plastisol coating wearing thin); cracks in fibre cement; deteriorating sealant at penetrations; missing or rusted fixings; visible structural deflection.

Internal condition. Look for: water staining inside the building (penetration); condensation marks indicating poor weather sealing; structural concerns at purlin level.

Asbestos testing. For pre-2000 buildings, sample test the cladding ($40-80 per sample via UKAS-accredited lab). The result determines whether direct PV is possible (positive fibre cement) or requires re-roof first (positive asbestos cement).

Combined re-roof + PV economics

For pre-2000 buildings with asbestos cement (the most common combined scenario):

• HSE-licensed asbestos cement removal: £30-50/sqm
• Profiled steel re-cladding: £45-80/sqm
• PV install on the new roof: £700-950/kW

For a 2,000 sqm livestock building:

• Re-roof cost: £150,000-£260,000
• PV cost (250 kW): £180,000-£237,500
• Total project cost: £330,000-£497,500
• Annual PV saving: £55,000+
• 25-year PV revenue: £1.4m+

The PV alone justifies its capex (typical 4.5-7 year payback). The ‘combined’ value is that the re-roof was needed anyway — so the PV business case extends to fund both elements as one investment.

When NOT to combine

Situations where the combined approach doesn’t work:

• Building scheduled for demolition or major use change within 5-10 years (PV economic life not achieved)
• Building’s structural frame is also compromised (frame replacement is a different scope)
• Roof condition is critical and replacement cannot wait for PV planning timeline (typically 6-12 months)
• Very limited capital with strict prioritisation (re-roof only, defer PV to later phase)

Phasing across multiple buildings

For multi-building farms with mixed roof conditions:

• Phase 1: PV on the building with the best roof (highest payback, lowest complexity)
• Phase 2: PV on the building with the second-best roof (typically 6-12 months later)
• Phase 3: Combined re-roof + PV on the older building requiring asbestos removal (typically 12-24 months after Phase 1)

This approach delivers fastest cash-flow generation while preserving capital for the more capital-intensive combined re-roof + PV in Phase 3.

What to do as a farm operator

For each building you’re considering for PV:

1. Confirm cladding type (sample test for pre-2000 buildings)
2. Assess remaining roof life (visual inspection + structural assessment)
3. Decide: direct PV install, or combined re-roof + PV, or defer PV until building replacement
4. Plan a multi-year programme prioritising the best-payback buildings first
5. Schedule asbestos and re-cladding work alongside PV install to capture mobilisation efficiency

We provide this assessment as part of every farm feasibility study. The structural and asbestos assessment is typically £400-£1,200 per building including sample testing — included in our standard scope when the project proceeds.

How we deliver combined re-roof + PV

Standard programme for a 2,000 sqm asbestos cement re-roof + 250 kW PV:

• Weeks 1-2: contract, kick-off, programme finalisation
• Weeks 2-4: G99 application submitted; asbestos contractor 14-day notification to HSE
• Weeks 4-8: procurement (panels, inverters, racking, cladding materials)
• Weeks 8-13: asbestos removal (5-week period for 2,000 sqm; full HSE-licensed work)
• Weeks 13-17: profiled steel re-cladding (4-week period)
• Weeks 17-20: PV install on new roof (3-week period for 250 kW)
• Week 20: commissioning and handover

Total project: 5 months from contract to commissioning. Single contractor coordinating asbestos removal, re-cladding, and PV install delivers material savings vs sequential delivery.