Patios by Constructora Acuña

​How to install polycarbonate roofing sheets for your patio

Johannes van Graan Johannes van Graan
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It’s a fact that some man-made materials, despite being useful in the construction industry, can still give off harmful fumes or gases if handled or disposed of incorrectly. But what’s the general consensus when it comes to polycarbonate translucent roof sheeting?

Polycarbonate is a versatile material used extensively as a roof light glazing. It is highly resistant to impact, transmits high levels of light, is relatively easy to use, and it has a good fire rating. 

This durable and practical roofing material is perfect for conservatoriespatios, terraces and deck areas, yet not recommended to be used as an entire roof for a house. And while it’s less aesthetically pleasing than tiles, tiles are completely opaque and won’t allow a glimmer of that South African sunshine to gleam through your patio roof. Or allow you to scope out that rainstorm while you sit, safe and dry, underneath it, right?

And even though we firmly advise that you allow a professional to take care of the physical installation process, it will go something like this…

Step 1: Safety first

First, make sure you have all the correct safety equipment. A scaffold and safety harness isn’t recommended, but crucial if you’re going to be working high up. Always exercise extreme care when walking on a roof; appropriate footwear is also necessary. Never walk on or apply your weight directly to sheeting.

Step 2: Right side up

Before installing, find a sticker showing you which side of the sheet faces the sun. It’s imperative that this is followed as there is only one side of the sheet that’s UV protected. The life of the sheet may be shortened and discolouration may occur if the unprotected side is exposed to the sun.

To start the installation process, lay out the purlin tape over the rafters to prevent expansion noise. Then cut your sheets to size. Sheets 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.

Step 3

Start with the lower sheets first, keeping the openings where the sheets overlap away from prevailing wind. Allow an overhang of 50mm into the gutter.

Step 4

Keep in mind that polycarb sheets naturally move with temperature, so you will need the correct fixings to allow this to occur without issues. Polycarbonate screws will pre-cut a hole wide enough to allow for this expansion, which will prevent the sheets from buckling. 

The large rubber on the screw will also seal on the sheet and stop any water from penetrating the roof. It’s important that your fixings go through the crest of the corrugations on your sheet.

Step 5

The frequency of screws required for corrugated and greca sheets is every 2nd crest for end purlins, every 3rd crest on the mid purlins and on Trimdek sheets use a screw on every crest. If you’re in a high-wind area, fix corrugated and greca sheets on every second corrugation on each purlin/ batten

Step 6

You need to tighten those fixings adequately to prevent rattling. But keep in mind that over-tightening may cause distortion and excessive stress with possible failure in the sheets. Please also only use the correct branded fixings as recommended by the manufacturer, as these are designed to be compatible with that specific brand of polycarbonate roofing.

Step 7

After installing all of your roof sheets you will need to finish off the structure with suitable metalgoods such as a ridge cap and barge caps. These will all fit over the top of your sheets and prevent air and water from penetrating your structure, thereby making it practical in addition to beautiful.

Next up: How to paint your unfinished wooden furniture.

Would you consider polycarbonate for your patio roof?
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