Skylight Replacement: Why Acrylic Is the Smart Choice

If you've got a yellowed, cracked, or leaking skylight, you're not alone. Skylights cop a lot of punishment — UV exposure, hail, thermal cycling, and decades of Queensland sun all take their toll. The good news is that skylight replacement doesn't have to mean calling a glazier and waiting weeks. With the right sheet material and a clean cut, most skylights can be replaced as a straightforward DIY or trade job.

This guide covers the materials used in skylight replacement, how to choose between them, what to measure, and how to get your sheet cut to size — so you can get light back into the room without the drama.

What Skylights Are Actually Made From

Most residential and commercial skylights are made from one of three materials: glass, acrylic (perspex), or polycarbonate. Glass is heavy, expensive to handle, and shatters on impact — which is why it's rarely used in flat or low-pitch skylight applications. The two plastics dominate the market, and for good reason.

Acrylic sheet — also sold under the brand name Perspex — is the most common skylight material. It's lightweight, optically clear, easy to cut, and transmits light exceptionally well. It does yellow over time with UV exposure, which is why you're probably replacing it now. Modern UV-stabilised acrylic grades hold their clarity significantly longer.

Polycarbonate sheet is tougher — it's virtually unbreakable — but it scratches more easily and can also yellow without proper UV coating. It's the better choice where impact resistance is a priority, such as in industrial buildings, skylights over machinery, or areas prone to hail.

For most residential skylight replacement jobs, UV-stabilised acrylic is the right call. It's cost-effective, widely available, and gives you the optical clarity you want from a skylight.

Acrylic vs Polycarbonate for Skylight Replacement

Choosing between the two comes down to your application. Here's a practical breakdown:

Choose acrylic when:

You want maximum light transmission (acrylic transmits around 92% of visible light, slightly better than polycarbonate). You're replacing a domestic skylight in a roof with a frame that supports the sheet. Budget is a consideration. You want a cleaner, more glass-like appearance. The existing skylight was acrylic and you're doing a like-for-like replacement.

Choose polycarbonate when:

The skylight is in an area exposed to impact risk — hail, falling branches, or foot traffic on the roof. You need a thicker, structural sheet that can span a larger opening without a full frame. The application is industrial or commercial. You need multiwall (twinwall or triwall) polycarbonate for insulation properties.

P&M Plastics stocks both acrylic sheet and polycarbonate sheet and can help you determine the right grade and thickness for your specific skylight replacement job.

Thickness: What You Need for a Skylight

Thickness matters more than most people realise. Too thin and the sheet will flex, bow, or crack under load. Too thick and you're adding unnecessary weight and cost. For skylight replacement, the general guidelines are:

3mm acrylic — suitable for small skylights (up to around 400 x 400mm) that are fully supported by a frame on all four edges.

4–5mm acrylic — the most common choice for standard residential skylights up to around 600 x 900mm. Provides enough rigidity to handle wind load and minor deflection.

6mm acrylic — recommended for larger spans, heavier frames, or where additional rigidity is needed. Also a good choice if the original sheet was 6mm.

If in doubt, match the thickness of the sheet you're replacing. Remove the old panel, measure it with a vernier or digital caliper, and use that as your reference. Don't guess — a sheet that's too thin will cause problems down the track.

How to Measure for a Replacement Skylight Panel

Accurate measurement is the most important part of a skylight replacement job. A panel that's even 5mm too large won't fit; one that's too small will leak. Here's how to measure correctly:

First, remove the old skylight panel if it's still in place. Measure the rebate — the channel or lip that the sheet sits in — not the visible opening. The sheet needs to overlap the frame by enough to be held securely and seal against weather. Typically this is 15–25mm on each side, but check your existing frame.

Measure in at least two places in each direction — frames can be out of square, especially in older buildings. Use the smaller dimension if there's a discrepancy, and confirm the frame is actually square before ordering. If it's not square, you may need to supply a template or exact corner-to-corner diagonal measurements.

Allow for thermal expansion. Acrylic expands and contracts with temperature — around 0.07mm per metre per degree Celsius. For a 1000mm panel in Queensland's climate, that's a meaningful movement. Don't cut the sheet to a tight fit; leave a small gap (2–3mm per side) and seal with a flexible sealant.

Getting Your Skylight Sheet Cut to Size

Once you have your dimensions, you have two options: cut the sheet yourself or have it cut professionally. For most skylight replacement jobs, professional cutting is the better choice. Acrylic can crack or chip if cut incorrectly, and a clean, straight edge is important for a good seal and a tidy finish.

P&M Plastics offers acrylic cut to size from our Gold Coast facility. You supply the dimensions, we cut the sheet to your exact specifications. Cuts are made on precision CNC equipment, so edges are clean and consistent — no chipping, no cracking, no rework.

If your skylight has a non-standard shape — curved edges, cutouts, or an irregular profile — our CNC router service can handle it. Bring in your old panel as a template, or supply a drawing with dimensions, and we'll cut it to match.

Installation Tips for Acrylic Skylight Panels

A few practical points to make your skylight replacement last:

Leave the protective masking on the sheet until installation is complete. This prevents scratching during handling and fitting.

Use a neutral-cure silicone sealant — not an acetic-cure (vinegar-smell) product, which can craze acrylic over time. Apply sealant to the frame rebate before laying the sheet, then seal the top edge once the panel is in position.

If using screws or fasteners, drill pilot holes slightly larger than the fastener diameter to allow for thermal movement. Never over-tighten — acrylic will crack around a fastener that's been torqued too hard.

Clean the new panel with a soft cloth and mild soapy water. Avoid ammonia-based cleaners (like window spray) — they degrade acrylic over time. For ongoing care, our acrylic care guide has everything you need to keep the panel clear for years.

Where to Source Your Replacement Skylight Sheet

P&M Plastics is a Gold Coast-based plastic fabrication company with full sheet stock and cut-to-size capability. We supply acrylic and polycarbonate sheet to tradespeople, builders, and homeowners across South East Queensland. Whether you need a single panel cut to size or multiple sheets for a commercial rooflight replacement, we can turn it around quickly.

Our cut-to-size plastic service is available for both trade and retail customers. Bring in your measurements, your old panel, or a drawing — and we'll get you sorted.

Need a skylight panel cut to size? Contact P&M Plastics on the Gold Coast — we stock acrylic and polycarbonate sheet and can cut to your exact dimensions, fast. Get in touch with our team to discuss your skylight replacement job.