Never stand on it
Laserlite, a polycarbonate sheet maker, says never to walk on its sheets or put your weight on them, and recommends safety mesh under installations more than 3 m up. On a steel roof with clear sheets, Lysaght tells roofers to stay at least one pan away from them. If a ball or branch lands up there, reach it from below with a pole or call a roofer.
What you're buying
Laserlite's corrugated sheet is a typical example: an 840 mm sheet covers about 760 mm once the side laps are allowed for. Grades differ. Laserlite says its 3000 range is 0.8 mm thick, comes in lengths up to 9 m and blocks up to 99.9% of UV.
Its 2000 and 3000 sheets carry a 10 year warranty against weather breakage from hail up to 25 mm across, and a light transmission warranty limiting loss to 11% over the first 15 years. Those are the maker's figures, so compare the terms on whatever brand you're quoted. We have no connection with Laserlite; we quote its guide because it's specific.
Over a patio: polycarbonate, steel or insulated panel?
| Polycarbonate | Steel sheeting | Insulated panel | |
|---|---|---|---|
| Light underneath | Lets daylight through | Blocks it | Blocks it |
| Sun's heat | Comes through with the light | Blocked, though the sheet itself gets hot | Blocked by the insulated core |
| Can a roofer walk on it? | Never | Yes, on the right spots | Follow the maker's guide |
| Lowest pitch | 5 degrees (Laserlite) | 5 degrees for corrugated, lower for some profiles | Depends on the product |
| Hail | Some makers offer a breakage warranty | BlueScope says dents don't usually shorten a Colorbond roof's life | Ask the maker |
What a good install looks like
Most problems come from fixing polycarbonate like steel. It expands and contracts a lot with temperature, so Laserlite says holes must be drilled oversize (10 mm for sheets up to 4.2 m, 12 mm for longer), with the screw centred and tightened only enough to stop rattling. It also sells a foam tape for between the purlins and sheets to quieten the creaking that movement causes.
The UV-protected side, the one with the label and inkjet printing, must face the sun; fitted upside down, a sheet can discolour and won't last as long. Laserlite wants a screw every second rib on end purlins and every third on the ones between, end laps of 150 mm on steep roofs or 200 mm on shallow ones, a 50 mm overhang, and side laps facing away from the prevailing wind.
Sealants are out. Laserlite says they can damage the UV layer and stop the sheet moving; if one is unavoidable, it should be 100% neutral cure and made for polycarbonate.
Keeping it clear
Wash it with warm soapy water and a soft sponge or brush, from the ground with a long handle where you can. Never use a water blaster: Laserlite says it strips part of the UV layer and shortens the sheet's life.
A cracked or discoloured sheet is a small job for a roofer to swap out, and it's worth doing before leaves and water work their way underneath.
What to ask the installer
- Which brand and grade are you quoting, and what does its warranty cover?
- What's the pitch, and does it meet the maker's minimum?
- How will you drill and fix the sheets to allow for movement?
- Will there be safety mesh underneath?
What you can do, and what you can't
You can
- Wash the sheets from below or the ground with a soft long-handled brush
- Check from underneath for cracks, loose screws or yellowing
Leave to a roofer
- Anything that means being on or above the sheets
- Replacing sheets and fixing leaks at laps or flashings
What we'd put up
Over a spot you want bright, like a clothesline area or a patio that doesn't get much sun, polycarbonate makes sense. Over an outdoor living area that cops the afternoon sun, we'd lean towards steel or insulated panel, perhaps with a couple of clear sheets for light. Either way, ask the installer to show you the UV label facing up before the screws go in.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.