One of the common enquiries we hear at The Plastic People is about roof glazing and we understand what a challenging task it is. Twin-wall and multi-wall polycarbonate tends to be the material we are mostly asked about by customers wanting to undertake a roofing project. This blog is written to offer some guidance.
Start off with a basic drawing of your roofing project. Show all sections of wall, roof and any existing support rafters. The purpose of this is to show the size of the area that you need to cover and to help you decide how many twinwall sheets you will need.
Deciding how much twinwall or multiwall you need. If you already have support rafters in place this will determine the size of each multi-wall sheet (eg it will be the size of the distance between your support rafters) and play a part in how thick your multi-wall sheets should be. Essentially the wider apart your support rafters are, the thicker the multi-wall you need to use. As a guide, if your support rafters are 980mm apart then 16mm thick multi-wall would be a minimum thickness for your roofing project. Due to varying factors of pitch, wind loading and snow loading we recommend that you do not exceed 1050mm distance between rafters. The narrower the widths the stronger your roof will be.
Choose your multiwall polycarbonate sheets. Sheets come in different sizes upto 5m x 2m. It is best to use sheets no wider than 1050mm wide to allow for adequate expansion and contraction. You can buy them cut to the size you need or you can cut them yourself using a fine tooth jigsaw or circular saw. Think whether you would like clear, bronze or opal twin-wall or multi-wall polycarbonate. Opal lets in less available light so may make a better choice if you want more shading
When you use your multi-wall, position the sheets so that their channels run vertically which will allow for condensation (if any) to drain. Bearing this in mind, the twin-wall or multi-wall polycarbonate sheets can be cut so that you get the best use of the material.
Select your fixings. Use your sheet dimensions as a guide to doing this – each joining sheet will require a glazing bar. You can buy gable bars where the last rafter is free standing and wall bars for the end rafters that butt against a rising wall. At the bottom slope we recommend closing the sheets off with an aluminium end stop bar which also helps to keep the multiwall sheet even more rigid. Glazing bars are normally supplied with necessary fixings and gaskets you require – like the ones here.