Fixing Polycarbonate Sheeting to Roofs

Published: 16th August 2011
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Polycarbonate roofing and cladding sheets are one of the toughest building and roofing materials to be developed in the construction industry in recent years. Believe it or not, polycarbonate sheets are over 200 times stronger than glass and, being almost 5 times lighter, offer innumerable possibilities to the builder, tradesman and DIY enthusiast.

The material's strength is in the twin-wall or triple-wall designs. It can deliver many more advantages to the construction industry, including:

• Its overall strength and shatterproof characteristics.

• Flexibility: the sheets expand and contract with climate and temperature changes in Great Britain and Europe. They are housed and secured in special 20mm aluminium glazing bars which are fixed to a building's roofing joists by screws. These glazing bars allow for any polycarbonate sheets' expansion or contraction, resulting from temperature changes.

• They deliver superb insulation, almost as good as a sealed unit double glazing system, but they are a lot less costly to purchase and install.

• Maintenance free: polycarbonate sheets only need to be washed using non-abrasive brushes and soapy water, and then hosed down for the removal of dirt.

• Up to 90% of available light can be transmitted through any polycarbonate panels, making them ideal for conservatory roofs; greenhouse roofs and walls; glazing panels and glazed porches; car port roofs or their partially-enclosed walls; and perfect for the roofing of workshops and sheds, or household garages and professional garage workshops as they let in the maximum daylight.

• Polycarbonate sheets are growing in stature and appeal, because where modern building design requires maximum natural light penetration and an aesthetic finish, the sheets have become a much improved alternative to the heavier, old-fashioned, wired glass panels or corrugated metal sheeting, and with considerably less weight to distribute across a building.

• They are perfect for delivering effective insulation on a gently sloping workshop or animal enclosure roof, and are far cheaper to install than the more costly, double glazing roof panels.

• Supplied in twin-wall or triple-wall designs for additional strength and insulation purposes.

• Their double-sided UV protection is resistant to yellowing in sunlight.

• They are supplied in 10mm and 16mm thicknesses.

• Sheet sizes: 2, 5, 3 and 4 metre lengths x 900mm standard widths. Other sizes can be found in specialist Builders' Merchants. Ask at your local suppliers before planning your polycarbonate roof installation.

Cutting to Size

Despite its enduring strength, polycarbonate sheets can easily be cut to size using a fine toothed electric power saw or hand saw. Always try to cut to a width close to the outside of the sheet's internal wall structures. Having an assistant holding the sheet and firming it up during sawing will prevent excessive vibrations from occurring.

Do not remove the polythene film covering until all of your sheets are cut to size and ready to fit.

Do not remove the seals on the end of each sheet, unless you are trimming a vertical panel to size, and then it is essential you leave the top end seal intact and only remove the seal at the bottom as you cut it to length. Apply a cover bead profile once the sheet has been cut to size and any dust fibres are removed from within. Do not leave dust or moisture in any of the sheeting flutes. Only use an airline to remove dust or debris in the flutes, even if this means temporarily removing the top edge seal, and replacing it afterwards. Always store polycarbonate sheets flat and in dry areas, not outside on grass or lawns.

Allow a 65 mm polycarbonate sheet overhang to deliver all rainwater off a roof and into any surrounding guttering.


Once cut and laid into place, each panel is held in position through a clever, snap down cover strip placed over the aluminium glazing bars. Add the glazing bars' end panels after you have snapped on the covers. They will provide a professional finish to your roofing glazing bars when fitted. At no time should a builder stand on polycarbonate sheeting when fitting it onto a roof. Protect your panels by using a plywood boarding sheet to spread any builder's body load across the panels and roof area. Aluminium glazing bars are screwed into the joists at 920mm centres to allow for the panels' eventual expansion [from 900mm] in warmer weather and any prevailing hot summer conditions.

Polycarbonate roofing sheets can be butted up to a house wall using lead flashing cut into the brickwork mortar and overlapping the panelling where a glazing bar and its surface cover has been placed next to the wall and supported by a horizontal wooden rafter stretched across the adjoining house wall.

In order to allow for heat expansion and contraction, a non-hardening silicone seal should be applied wherever advised. Ask at your Builders' Merchants supplier for advice on using the right flexible silicone sealant on the carbonate roof structure.

Extra Fixing and Protection

With the prevailing weather in Great Britain becoming more extreme, we strongly advise all DIY enthusiasts and builders to add an EXTRA fixing button screw in the centre of each carbonate roofing sheet near the bottom edge and screwed into a wooden rafter; plus add a further button in the centre of each supporting wood purlin.

Drill the roof button entry hole to a 15mm diameter to allow for heat expansion of the polycarbonate sheeting. Add the foam washer to the underside of the screw head. Drive in the screw and fit the head cover without making the application too tight as this could distort your roofing sheet.


Polycarbonate roofing sheets are supplied together with roofing trims, including universal edge flashing, anti-dust tape, polycarbonate roofing button fixing sets, plus universal glazing bars, covers and end cover caps. Polycarbonate end bead profiles are also available for fixing and sealing any sawn and shortened roof panels. Everything is available to create a professional finish.

The Right Tools

Fitting polycarbonate roofing, you’ll need the following tools:

Power drill, drill bits and driver. Electric power saw. Hoover (to collect dust after cutting a sheet).

Goggles and a facial dust mask.

Power tools will cut down on the amount of time it takes to complete a job and ensure a perfect finish to your cutting and installing.

Advantages of Polycarbonate Roofing

Polycarbonate roof panels offer many advantages to building contractors, roofing contractors, farmers and DIY enthusiasts, including cost savings, good insulation and easy to install, lightweight materials.

Talk to your local Builders' Merchants trade experts today about the benefits of polycarbonate roofing panels.

David writes on behalf of Anglia Tool Centre, a leading stockist and supplier of power tools within the UK. Supplying advice, guidance and DIY equipment to home owners, professionals and DIY enthusiasts.

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