Inspect the membrane before fixing the array layout

An aerial image shows open space. A roof inspection reveals seams, repairs, drains and different construction phases. Map areas that can be retained, areas needing repair and sections requiring renewed waterproofing before finalising the array.

This simple distinction gives the roofing contractor and PV installer a shared starting point. It can prevent the preferred layout from occupying an unsuitable or inaccessible part of the roof.

Retained and renewed membranes need different approaches

A mineral layer may be installed above suitable retained bitumen waterproofing. VLOEI is applied to prepared mineral-surfaced bitumen; its datasheet specifies 3 mm thickness and individual substrate suitability assessment. WEER is the board alternative above waterproofing beneath PV.

When the membrane is renewed, SHEET can be placed on insulation beneath it. The construction sequence is different because the board becomes part of the membrane substrate. Our roof-layer guide explains this early decision.

Check the actual load path

Dividing total weight by roof area is only a first indication. PV feet transfer forces through limited contact areas. Ballast, maintenance and wind affect the loads at particular locations. The roof assembly must transfer them to the supporting structure.

Combine module and ballast layouts with mounting-system load data. RVO identifies this information as part of structural roof assessment. Include the actual mass of the protective layer; it does not create spare structural capacity. [2]

Keep drainage accessible beneath the installation

Decide how drains, leaf guards and surrounding details will be inspected after installation. Protection boards and supports must not create unintended water barriers. Access should be visible on the plan rather than left for a maintenance team to improvise.

WEER is intended for direct installation on the named membranes without a generally required separation layer. Drainage and wind restraint remain separate design details. For VLOEI, preparation, interfaces and specified thickness belong in the installation method.

Use an agreed first section to resolve interfaces

A small initial work area helps both trades see where a protective layer ends, how a drain stays accessible and where a cable route runs. It does not replace technical evidence, but makes the intended detail tangible. VdS 3145 provides further general guidance for planning and operating PV systems. [1]

Prepare a useful project enquiry

Send roof photographs, a section and the proposed array layout. Include membrane type, roof condition and programme. VlamShield can then compare VLOEI and WEER above retained waterproofing, or SHEET beneath a new membrane, with the interfaces and sequence in view.

Choose the protective layer from the actual roof condition and assembly, then develop the installation detail around it.