Lessons learned on-site

By Steve Pester, BRE

With the new push towards PV installations on commercial roofs, Steve Pester, BRE, runs through tips for best practice garnered via BRE’s own 32kWp system, and its numerous inspections of others

If you are an installer who is just dipping your toe into the commercial roofs market, or thinking about it, here are a few on-site issues that can happen in real life:

  • FiT deadlines – as in the domestic market, these cause huge dashes to get systems commissioned before the degression date. Extra checks on workmanship are needed if working to tight deadlines.
  • Out-of-hours work may be required to hit the deadline, but it may also be required in order to avoid noise and disruption to the building occupants.
  • ‘Flat’ roofs are not usually flat! They have a drop-of for drainage and are often uneven; you may need to allow for this in the mounting design.
  • You absolutely must have someone who is competent to do correct wind loading calculations for you. A new version of the well-known BRE Digest 489 has been published, which gives guidance on this issue.
  • You must also use a professional to assess the roof type and strength before deciding on the method of restraint. If you are using ballast, double-check that the materials delivered are to specification (e.g. BS EN 1339 for slabs
  • Obviously, you must have a good, clear method statement before starting work, covering all aspects of the installation. For example, how will the personnel be safe when working at height?
  • If you need permanent guard rails, have these been allowed for in the shading assessment?
  • Plan the safe movement of materials meticulously. If you intend to crane the materials onto the roof, think about what will happen in windy conditions. Are there any nearby occupied buildings?

An information paper with fuller details of these and other issues will shortly be available on the National Solar Centre website and a new code of practice will shortly be available from the IET.