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Installing Polycarbonate Roofing Sheet

There are 3 key steps to follow when installing Polycarbonate Roofing Sheets. We hope by following the steps below, you will achieve a safe and successful project.

Step 1 - Preparation

- Check that the pitch of your roof is at least 5°(or 88mm rise per metre.)  This will ensure adequate water drainage.

- You must allow for ventilation, especially at the highest point, to minimise heat build-up and provide effective air circulation. Good ventilation will also minimise the chances of condensation forming.

- For roofing, purlin/batten spacings should be no more than those shown in the table below:

 

Profile

End Span (mm)

Mid Span (mm)

Corrugated

800

1000

Greca

900

1200

Trimdek

900

1200

Note:For walls, nogging spacings should be no more than 1200mm.

- Use Noise Stop Tape to avoid creaking caused by the sheet expanding & contracting. Buy Noise Stop Tape here

- Also use Eave Infill Strips at eaves to avoid rain, dust & wind entering. Buy here

- For installations under a gutter, neaten up around the sides with flashing

STEP 2 – Fixing your sheets

- Ensure that the UV protected side faces upwards. This is normally the side the label is on.   When installed as a wall or fence it is recommended that the UV protected side is facing the most sun during the day.

- The sheet can be easily cut with a pair of shears, a fine-toothed handsaw or a circular saw with a cut-off blade suitable for plastic

- When laying the roof, start with the lower sheets first, keeping side laps away from the prevailing wind. Allow an overhang of 50mm into the gutter. Temperature changes will cause expansion and contraction, so make allowances for thermal movement. Resistance to movement can cause buckling.

- Side laps differ slightly by profile. For corrugated profiles you need 1.5 corrugations. For all other profiles 1 corrugation is sufficient.

- To ensure maximum performance and to avoid buckling, it is necessary to oversize the holes and centre the fixings. It is recommended that Clearfix self-cutting screws are used. (you can buy these here) They come complete with their own hole saw that cuts an expansion hole as you insert them. The screw is centred every time and the cutter holds the plug of material removed. If using polycarbonate screw & dome seal screws (buy these here), pre-drill your fixing holes. Use a 10mm drill for sheets up to 4.2mm long and a 12mm drill for sheets longer than 4.2mm. Fix the sheet through the centre of the pre-drilled holes, perpendicular to the purlins/battens. A (5/16”) Drill hex driver bit should be used (buy this here). Only tighten the fixings enough to prevent rattling. Over tightening may cause distortion and undue stress with possible failure resulting. In normal conditions, use the fixing spacings shown below:

 

Profile

End Purlin

Mid Purlin

Corrugated

Every 2nd Crest

Every 3rd Crest

Greca

Every 2nd Crest

Every 3rd Crest

Trimdek

Every Crest

Every Crest

 

As a guide, you will need approximately 7 fixings per metre. This will depend on your purlin spacings and usual wind conditions. In high wind areas fix Roma and Greca on every second corrugation on each purlin/batten. It is suggested that barge capping be used. Fix the sheet through the valleys for walls with polycarbonate screw and dome seals.

- End overlaps should be 150mm for steep pitch or 200mm for shallow pitch

STEP 3 – Cappings & flashings

- For an Apex roof:

Use barge capping to the edge of the sheet and ridge capping to the apex. Secure using Clearfix self- cutting screw and dome seals. (buy all these products here)

- For under a gutter, against a wall: Fit flashing and make weather tight

- for edge of fascia:Fit barge capping to neaten up edge. Secure using Clearfix self cutting screw & dome seals

To download this page in a printable PDF format, click here