Most skylight dome replacement jobs start the same way. The dome has gone hazy or yellow, fine cracks have crept out from the corners, and the light coming through is a fraction of what it used to be. Left long enough, an acrylic dome that has spent twenty years under the WA sun will crack through on its own or shatter the first time it takes a decent hailstone.

BCJ Plastic Products vacuum-forms replacement domes at our Perth workshop, in acrylic or polycarbonate, to whatever size you need. That matters more than it sounds. A large share of the skylights on Perth roofs were installed by companies that no longer exist, in sizes nobody stocks any more, which is exactly the job an off-the-shelf catalogue cannot solve.

Signs your skylight dome needs replacing

Plastic skylight domes do not fail suddenly. They degrade over years, and the warning signs appear well before anything breaks.

Yellowing and hazing. The clearest early sign. UV exposure gradually breaks down the surface of the plastic, which scatters light instead of transmitting it. If the room below has quietly got darker over the last few years, the dome is the reason.

Crazing. A network of fine surface cracks, usually starting at corners and around fixings where the material is under the most stress. Crazing means the plastic has become brittle. It will not stop or reverse.

Brittleness. A dome that has gone brittle will crack rather than flex. If you can hear it creak or tick as it heats and cools through the day, it is near the end.

Visible cracks or holes. At this point water is already getting in, even if you cannot see a drip yet.

Chalky white residue. A powdery surface film that comes back after cleaning is degraded material, not dirt.

One thing worth checking before you order anything. If your only symptom is a leak with no visible damage to the dome itself, the problem is more likely the flashing, the seal or the upstand than the plastic. Replacing a perfectly good dome will not fix a flashing leak.

Acrylic vs polycarbonate skylight domes

Both work. They fail differently, and the right choice depends on what your roof is actually exposed to.

For most domestic skylight dome replacement work in Perth, acrylic is the right answer. Cast acrylic holds its clarity for a very long time under UV and costs less, and the impact advantage of polycarbonate rarely justifies the price on a suburban roof.

Polycarbonate earns its place where impact matters. Industrial and warehouse roofs, sites with a genuine hail history, anywhere the skylight is walked near, or spans large enough that a brittle sheet becomes a hazard rather than an inconvenience.

If you go polycarbonate, the UV layer is not optional. Uncoated polycarbonate yellows noticeably within a few years in WA conditions, which defeats the point of paying more for it in the first place.

How to measure for a replacement dome

Getting the sizes right the first time saves a second trip onto the roof. Measure and photograph the following before you get in touch.

1. The base dimensions. Measure the outside of the dome’s flange, the flat lip that sits on the roof, both length and width. Do not measure the glass area or the internal opening.
2. The rise. The height from the flange to the highest point of the dome. This determines the profile and it is the measurement most people forget.
3. The corner radius. Most rectangular domes have rounded corners rather than square ones. A rough radius is enough.
4. Skin count. Look at the edge of the dome. A single skin is one layer of plastic. A double skin has two with an air gap, used for insulation and to reduce condensation.
5. Photographs. One straight down from above, one from the side showing the profile, and one of the flange edge.

If the dome is broken or missing, measure the upstand or kerb it sat on and tell us. We can work back from that.

Skylight cover replacement for commercial and industrial roofs

Skylight cover replacement on a factory, warehouse or workshop roof is a different job to a domestic dome. The panels are usually larger, often profiled to match the roof sheeting, and the consequences of leaving a degraded one in place are more serious.

A skylight panel that has gone brittle looks identical to a sound one from underneath. On an industrial roof that is a genuine fall hazard, because a degraded panel will not hold the weight of someone who steps or falls onto it, and roof sheeting gives no warning of where the panel starts. Anyone maintaining an older industrial roof should treat aged skylight panels as a safety item rather than a maintenance one.

We supply replacement covers and panels in acrylic and polycarbonate to suit commercial and industrial applications, cut and formed to the profile and size required. We also supply flat sheet plastic cut to size if you would rather form or fit the panels yourself. Send the sheeting profile along with your sizes and we can match it.

Skylight dome replacement questions we get asked