Verandah Restoration and Repair – Polycarbonate Roofing Project (Dingley Village)

Project location: Dingley Village, Melbourne

The existing verandah roof was fitted with corrugated polycarbonate sheets that had been in place for over a decade. The sheets were showing clear signs of ageing and yellowing, and the customer wanted to replace them with a clear, glass-like polycarbonate roofing solution.

The verandah had a slope of more than 5 degrees, with an existing gutter and frame in good condition. Timber rafter spacing was 800mm centre-to-centre, with battens (purlins) sitting on top of the rafters.

Choosing the Right Polycarbonate Roofing Installation Method

There are two common ways to install polycarbonate roofing onto a supporting structure:

1. On top of purlins/battens — Fixing screws pass through aluminium joiners and into the purlins to hold the sheets in place. This is the most common method when battens are already present.
2. On rafters only — Used when there are no purlins. Aluminium H-bar joiners sit directly on top of the rafters.

For this project, the sheets were installed on top of the existing purlins.

Product Selected: Excelite W800 Solid Polycarbonate Locking System

After consultation, the customer approved the Excelite W800 Solid Polycarbonate Locking Roofing System — a flat sheet system with standing edges that lock securely into aluminium H joiners, providing excellent waterproofing without penetrating the sheet surface.

• Sheet thickness: 4mm
• Colour: Clear (transparent)
• Length: 3,600mm (standard size — zero wastage for this project)
• Sheets used: 7

The Excelite team completed the full removal of the old roofing and installation of the new system in a single day. All edges were covered with flashing, except at the sides where water drains into the existing gutter.

How Much Overhang Should Polycarbonate Roofing Have Into the Gutter?

As a general rule, polycarbonate roof sheets should overhang 50mm into the trough of the gutter to ensure proper water drainage.

Accurate measurement of the overhang and drip edge is critical — any incorrect cuts to polycarbonate are irreversible. Take extra care during the measurement phase before cutting.

How to Stop Cracking and Creaking Noises from Your Pergola Roof

Two types of noise are common when polycarbonate roofing is not installed correctly:

1. Thermal Expansion Cracking

If polycarbonate sheets are screwed directly into the frame without an expansion gap, the sheets will crack and pop as temperatures change throughout the day. This is caused by the natural thermal expansion and contraction of polycarbonate.

Solution: Use aluminium joiners instead of direct penetration fixings, and leave adequate expansion space within the joiner channels.

2. Wind-Induced Rattling

When polycarbonate sheets make direct contact with purlins (battens), wind movement causes rattling and creaking — particularly noticeable in Melbourne's variable weather conditions.

Solution: Apply anti-noise foam tape to the top of all battens before laying the polycarbonate sheets. The tape cushions the sheet, eliminates direct contact with the timber, and significantly reduces noise.

Anti-noise tape is placed on the purlins (the battens running perpendicular to the sheet direction) before the polycarbonate is laid. Fixing screws pass through the tape. It does not need to be applied to the rafters.

Project Result

The completed verandah now features a clean, glass-like appearance with excellent light transmission, proper waterproofing, and a noise-free installation. The customer was able to retain the existing frame and gutter, keeping the project cost-effective.

Considering a similar verandah or pergola roofing upgrade? Browse our Solid Polycarbonate Locking Roofing System or contact the ExcelitePlas team for a consultation.