Polycarbonate canopies for schools: what you need to know

Why polycarbonate is the usual choice

Walk round most schools with a canopy and the roof will be polycarbonate. It is a tough, clear plastic that is far lighter than glass, much harder to break, and lets daylight reach the space underneath and the classrooms next to it. It can be curved, so it suits curved and wave roofs as well as straight ones, and it costs less than glass.

The main alternatives are steel sheet, which is cheaper but blocks the light, glass, which looks smart at entrances but is heavy and costs much more, and fabric, which is used for shade sails and tensile canopies.

Solid or multiwall sheets

Polycarbonate roofs come in two main forms.

Solid sheet

A single solid sheet, often 3 mm to 6 mm thick on canopies. It is the clearest option, looking almost like glass, and very impact resistant. It shows dirt and scratches more and lets more heat through.

Multiwall sheet

Two or more layers joined by internal ribs, like a very stiff corrugated card. Thicknesses range widely; one published aluminium school canopy uses 35 mm structured polycarbonate panels. Multiwall sheets are lighter for their stiffness, span further between rafters and diffuse the light, so there are fewer harsh shadows. They are less clear and the ribs can collect dirt or algae at the ends if they are not sealed.

Clear, opal or tinted

The colour of the sheet matters more than people expect.

• Clear lets the most light through. Good next to classrooms that are already dark, but the space underneath can get hot and bright in summer.
• Opal is milky white. It diffuses the light, cuts glare and reduces heat build-up. It is a common choice for playground and dining canopies.
• Bronze or tinted cuts heat and glare further but makes the space darker.

Ask for the sheet’s light transmission and solar heat figures and compare like with like. If a canopy sits in front of classroom windows, think about how it will change the light inside.

Safety: fragile and non-fragile roofs

Schools have one worry that homes do not: pupils climbing, and balls or bags landing on the roof. A fragile roof is one that could give way under a person’s weight. Ask the installer to confirm in writing whether the roof as installed has been assessed as non-fragile, and on what basis, including the sheet type, thickness and how it is fixed. Also ask how the design deters climbing, such as smooth posts and gutters out of reach.

Wind, snow and site calculations

A canopy roof is a big, light surface that wind tries to lift. Polycarbonate sheets have to be fixed and supported to suit the loads at your site, which depend on where you are, how high the canopy is and how exposed the spot is. Ask for site-specific structural calculations covering wind and snow, not just a generic rating. One published school walkway system lists a wind resistance of 23 m/s, which shows the kind of figure to ask for and compare.

Lifespan and warranty

Good polycarbonate sheets have a UV protective layer on the outside face. Without it, the sheet yellows and becomes brittle. Check that the sheet is installed the right way up, and ask for:

• the sheet warranty, which is often separate from the frame warranty
• the frame warranty, for steel or aluminium
• what the warranty requires, such as cleaning or inspections

Cleaning and maintenance

Polycarbonate is easy to look after if you avoid the wrong products.

• Clean with mild soapy water and a soft brush or cloth.
• Avoid abrasive pads and strong solvents, which can scratch or cloud the surface.
• Clear leaves from gutters each autumn so water does not back up.
• Check the end caps and seals on multiwall sheets once a year.
• Never let staff walk on the roof to clean it unless it is designed and assessed for access.

How it compares on price

Most school canopy prices quoted per square metre assume a steel frame with a polycarbonate roof. Published installed prices run from about £350 to £750 per square metre before VAT, with the higher rate for small canopies up to 50 square metres and the lower rate for large areas over 100 square metres.

Frame style changes the price more than the sheet does. On one supplier’s published list prices, a curved roof starts about 8% above a straight monopitch roof, a wave roof about 23% above, and a cantilever about 29% above. Glass roofs are usually priced on survey and cost noticeably more.

Our school canopy price guide uses these figures to give a range for your size and style.

Polycarbonate for different canopy types

• Playground canopies: opal multiwall or solid sheet is common, for diffuse light and less heat.
• Covered walkways: clear or opal sheet keeps routes and nearby windows light.
• Entrance canopies: solid clear sheet or glass for a smarter look.
• Dining canopies: opal or tinted to keep eating areas cooler.

Questions to ask an installer

1. Solid or multiwall, and what thickness?
2. Clear, opal or tinted, and what are the light and heat figures?
3. Is the roof as installed assessed as non-fragile?
4. Are there site-specific wind and snow calculations?
5. What are the sheet and frame warranties, and what keeps them valid?
6. How are rainwater and leaves dealt with?

A polycarbonate canopy is a sensible default for most school canopies. Get the sheet, colour and safety details in writing, and two quotes on the same specification are easy to compare.