We’re planning on doing an extension to our house at some point in the not too distant future and are not 100% sure what the impact will be on the existing roof structure. Can you please provide details on the previous ground installed system with particular reference to the support structure?
From review of the SEAI code of practice for installers, it would appear that it is up to the installer to determine the suitability of the support structure as opposed to any particular building regulations. Perhaps the previous installers can offer guidance on this?
Below are extracts from the SEAI Code of Practice for the Installer.
4.3.4. Ground and Car-Port Mounting Systems - Installation
When considering a ground mounted or car port mounted PV system the Installer must assess the
• The design and specification of the PV ground or carport mounting system shall consider the
requirements of Section 4.3.2 and
- Strength and suitability of the ground area, soil conditions, stability, and risk of subsidence
- Ground mounted systems over exposed soil/grass, shall have a minimum clearance of
300mm from the ground level to the bottom of the solar PV modules to allow for
vegetation/grass growth, and maintenance of same.
- Cables from the ground mounted system to the dwelling shall be installed underground, in
a suitable duct.
4.3.2. Roof Mounting Systems – Loading and Structure
When considering roof mounted PV system, the Installer must consider and assess the below.
• The design and specification of the PV mounting system for all installation types shall consider;
- Building Regulations TGD A – Structure.
- Building Regulations TGD D – Materials and Workmanship.
- SR 50-2 “Code of Practice for Building Services Part 2: Thermal Solar Systems” and Agrément
Certificates for Solar Thermal and Solar PV systems.
- Site specific design wind and snow loads – derived from Eurocode-1 (and Irish National
- Appropriate safety factors – derived from Eurocode-0 (and Irish National Annex).
- Strength and suitability of the supporting structure.
- Strength of the fixing – using fixing data from Eurocode-5 (for standard fixings).
- Proposed mounting system and suitability for roof supporting structure and roof tile system.
- Weather sealing of any impacted parts of the roof for mounting system and cable access.
- Impact of any additional stress or strain on the overall roof structure and roof tile system,
particularly over time and during multiple temperature changes.
• The roof structure shall be checked to ensure it can withstand the imposed loads from the solar
PV system. This should include a site inspection by a competent person.
• Where there is any doubt to the suitability of the roof structure to withstand the imposed
loads, a qualified structural engineer should be consulted. Reasons for consulting a qualified
structural engineer may include, but are not limited to;
- Signs of structural distress
- Signs of post construction modification
- Shallow roof pitch (<30°)
- Roof design has potential for snow build up (e.g., dormers, valleys, parapets)
- The roof is an unusual, non-standard, construction.
• The Installer must retain documentary evidence of the calculations and assessment undertaken
in the design of the mounting system showing that site specific structural and wind risks have
been considered appropriately in the design.