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Case Studies
25 Mar 2026
by Gray Gibson

Solar Risks: When Solar PV is Installed on End-of-Life Roofs

As rooftop solar becomes more common, NFRC businesses are reporting that more systems are being fitted without an adequate assessment of the roof beneath.

This case study highlights the risks of installing solar PV on roofs that are already at, or close to, the end of their service life. Without a thorough roof condition survey before installation, there is a risk the roof will fail long before the solar system reaches the end of its 20–30-year design life.

Industry Perspective

Josh Morrison, Director at JR Roofing Lancs Ltd and NFRC North West Regional Chair said: “Over the last decade we have seen a huge push towards solar, and rightly so. It is a brilliant long-term investment when installed properly.

“However, we are increasingly attending properties where solar panels have been fitted onto roofs that were already at, or very near, the end of their lifecycle. In many cases, no thorough roofing assessment was carried out prior to installation.”

He added: “Solar installation is not just an electrical job. It is a roofing decision too. “A roof should have sufficient remaining lifespan to justify a 20-to-30-year solar system being mounted to it. If it does not, the correct approach is simple. Address the roof first.”

How Solar PV Affects the Roof

Solar PV directly alters the existing roof system, whether it is an in or on roof system that is being installed.

  • Fixings penetrate the roof covering.
  • Panels add weight to the structure.
  • The array changes how water drains across the surface.

If the roof is already nearing the end of its life, failure is more likely to occur well before the solar system itself needs replacing. Common consequences can include: 

  • Premature roof failure and deterioration of roof coverings
  • Water ingress and leaks beneath the panel array
  • Restricted access for inspection and repair
  • Costly removal and reinstatement of panels if the roof fails prematurely
  • Disputes between trades over responsibility

Morrison commented: “That is a costly and frustrating situation for property owners and clients, and it is completely avoidable. This is not about criticising electrical contractors or dedicated solar installers. It is about bridging the gap between trades and raising standards across the industry.”

The Solution

The most important element of safeguarding is ensuring the contractor carries out a pre-installation roof condition assessment before committing to installing solar. If the roof does not have sufficient remaining lifespan, it should be replaced before solar panels are fitted.

Solar should be a long-term investment. Installing panels on a roof that is already near failure creates avoidable cost, disruption, and risk for homeowners.

MCS Solar Design and Installation Requirements

The Microgeneration Certification Scheme (MCS), sets the standards for solar PV design and installation. The current Solar PV: Installation Standard (MIS 3002: 2025 ISSUE 1.0) states:

“The MCS Contractor shall ensure the building is assessed by a competent professional experienced in solar photovoltaic systems to ensure that it is suitable for the installation and, by undertaking the proposed works, the building’s compliance with the Building Regulations (in particular those relating to energy efficiency) is not compromised.”

In practical terms, this means an MCS Contractor is required to ensure the roof and building are properly assessed before installation. The assessment must confirm:

  • The building is suitable for solar PV.
  • The proposed works will not compromise compliance with Building Regulations.

NFRC recommends that MCS Contractors appoint an NFRC Member with relevant solar experience to carry out this assessment. If you are a homeowner, it can be worthwhile to ensure your solar installer has consulted appropriate roofing expertise during this process, or if they are using internal staff, ensure that this staff has the appropriate competencies. An experienced roofing contractor will understand how the solar installation affects:

  • Weatherproofing Structural performance
  • Long-term durability

This helps ensure the correct course of action is identified early, whether that is proceeding with installation, carrying out roof repairs first, or replacing an end-of-life roof.

MIS 3002 goes on to further emphasise that “PV systems should not adversely affect the weather tightness or structural integrity of the building to which they are fitted. The system should be designed and installed to ensure this is maintained for the life of the system.” Where an NFRC Member is not used, MCS Contractors must still undertake appropriate due diligence. They must satisfy themselves that the professional appointed has the necessary roofing and solar competence to:

  • Assess the condition and remaining life of the roof Identify defects or risks
  • Advise whether remedial works are required before installation

Failure to carry out a competent assessment risks non-compliance with MCS standards, premature roof failure, and avoidable remedial costs.

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