Ballasted systems
Ballasted mounting uses concrete or steel weight to hold the PV array against wind uplift, no penetration of the roof membrane. Standard for membrane roofs (single-ply, EPDM) and increasingly for profiled steel where roof warranty would be voided by mechanical fixing. Typical ballast load 15-20 kg/sqm.
Mechanically fixed systems
Mechanical fixing penetrates the roof to attach to structural purlins beneath. Lower dead load (5-10 kg/sqm) but penetrates the membrane — requires careful waterproofing detail and may void roof warranty. Standard for profiled steel where structural reserve is lower.
Wind loading to BS EN 1991-1-4
All mounting designs must withstand site-specific wind loading per BS EN 1991-1-4 (Eurocode 1). Coastal and exposed sites require higher wind loading specification. We have completed installs at port sites with 35 m/s design wind speeds — design envelope is well-defined.
Sprinkler clearances
LPC sprinkler clearances mandate 1m clear to deflector and 0.6m at high-bay spray heads. PV layout must respect these. Sometimes existing sprinkler heads need relocation to achieve target system size.
Common questions
Ballasted or mechanically fixed?
Depends on roof type and warranty considerations. Membrane roofs: ballasted only. Profiled steel: either, but ballasted increasingly preferred to preserve roof warranty. Mansard/pitched: mechanical only.
Will mounting void our roof warranty?
Mechanical fixing typically does void the roof warranty. Ballasted does not. We work with the roofing manufacturer (Kingspan, Tata, Corus) on warranty preservation where critical.