Polycarbonate sheets are known for being easy to work with, but small mistakes during installation can cause problems later. Leaks, noise, movement, or reduced lifespan often come down to a few avoidable issues.

If you’re planning a pergola, patio, or carport, it’s worth getting these basics right from the start.

1. Not allowing for expansion and contraction

Polycarbonate expands and contracts with temperature changes. If sheets are fixed too tightly, they can warp, crack, or make noise over time.

What to do instead:
Allow a small gap around fixings and edges so the sheets can move naturally.

2. Incorrect sheet orientation

Some sheets have a UV-protected side that must face upward. Installing them the wrong way reduces their lifespan.

What to do instead:
Check the label or protective film before installation and make sure the UV side faces the sun.

3. Using the wrong fixings

Standard screws without proper washers can lead to leaks or stress points in the sheet.

What to do instead:
Use fixings designed for polycarbonate, with sealing washers to keep water out and reduce pressure on the sheet.

4. Poor support spacing

If the structure underneath isn’t spaced correctly, sheets can sag or flex too much.

What to do instead:
Follow the recommended support spacing for your specific sheet type.

5. Sealing edges incorrectly

For multiwall sheets, sealing the ends the wrong way can trap moisture or allow dust and insects inside.

What to do instead:
Use the correct tapes and closures so the sheets can breathe while staying clean.

6. Ignoring roof pitch

A flat or low-pitch roof can lead to water pooling instead of draining properly.

What to do instead:
Make sure your structure has enough slope for water runoff.

7. Cutting sheets without proper tools

Rough cuts can lead to cracks or uneven edges, especially with solid sheets.

What to do instead:
Use sharp, appropriate tools and support the sheet properly while cutting.

Getting it right from the start

Most installation issues don’t come from the material itself, they come from small details being overlooked. Taking the time to plan properly will save you from fixing problems later.

Need guidance?

If you’re unsure about sheet type, spacing, or installation details, Polyguru can help you choose the right setup before you start.